13. Habitat restoration and creation
© Book authors, CC BY 4.0 https://doi.org/10.11647/OBP.0234.13
Background
Habitat destruction is one of the largest threats to mammal species and populations and habitat protection remains one of the most important and frequently used conservation interventions. However, in many parts of the world, restoring damaged habitats, improving habitats through altering management regimes or creating areas of new habitat may also be possible.
Habitat restoration or creation is often required by law as a response to activities that destroy large areas of natural habitats. Restoration activities may include planting vegetation, removing invasive species or creating breeding or shelter habitats, for example.
Studies describing the effects of interventions that involve restoration through processes such as fire and water management are discussed in the chapter Threat: Natural system modifications, and those that involve the control of invasive species in the chapter Threat: Invasive and other problematic species and diseases.
13.1. Remove topsoil that has had fertilizer added to mimic low nutrient soil
https://www.conservationevidence.com/actions/2544
- We found no studies that evaluated the effects on mammals of removing topsoil that has had fertilizer added to mimic low nutrient soil.
’We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.
Background
Removing topsoil may help to reduce fertility of soils as well as removing seeds that are found in topsoil. Both of these outcomes may help the establishment of native plant species, which may in turn influence the abundance of mammal species.
13.2. Manage vegetation using livestock grazing
https://www.conservationevidence.com/actions/2545
- Six studies evaluated the effects on mammals of managing vegetation using livestock grazing. Four studies were in the USA1–4, one was in Norway5 and one was in Mexico6.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): A replicated, controlled, before-and-after study in the USA4 found that introduction of livestock grazing increased the abundance of Stephens’ kangaroo rat after two years.
BEHAVIOUR (5 STUDIES)
- Use (4 studies): One of four studies (three replicated controlled studies and a before-and-after study), in the USA1,2,3 and Norway5, found that sheep-grazed pasture was used by feeding reindeer more than was ungrazed pasture5. One found mixed effects on Rocky Mountain elk use of grazed plots1 and another found no response of Rocky Mountain elk to spring cattle grazing2. The forth study found cattle grazing to increase the proportion of rough fescue biomass utilized by elk in the first, but not second winter after grazing3.
- Behaviour change (1 study): A replicated, paired sites study in Mexico6 found that in pastures grazed by cattle, Tehuantepec jackrabbits spent more time feeding than they did in pastures not grazed by cattle.
A before-and-after study in 1948–1974 in a predominantly grassland wildlife management area in Oregon, USA (1) found that when cattle grazing was reintroduced, there was a mixed effect on Rocky Mountain elk Cervus canadensis abundance. Four years after cattle were first reintroduced, elk numbers (325) were similar to those before cattle reintroduction (120–500), although disturbance by snowmobiles during this period may have reduced abundance. After nine years, elk numbers (1,191) were higher than before reintroduction (120–500). In 1960 the site was designated as a wildlife management area. Cattle grazed ceased in 1960 but was reintroduced in 1965 at a rate of 340 animal unit months (AUMs — a grazing measure based on forage requirement). Cattle grazing was increased to 700 AUMs in 1967 and 900 AUMS in 1969–1974. Cattle grazing was managed to optimise forage conditions and prevent accumulation of residual unpalatable vegetation. Elk were counted from horseback, along fixed routes, five times each winter, in 1948–1974.
A randomized, replicated, controlled study in 1971–1974 of a grassland in Washington, USA (2) found that spring grazing by cattle did not increase pasture use by Rocky Mountain elk Cervus canadensis nelsoni the following winter. There were no significant differences in the numbers of elk using cattle-grazed and ungrazed plots in the first winter (grazed: 60; ungrazed: 68 elk days/ha) or third winter (grazed: 38; ungrazed: 51 elk days/ha) after cattle grazing commenced. In the second winter, fewer elk used grazed plots (71 elk days/ha) than used ungrazed plots (98 elk days/ha). Three plots (9.3 ha each) were randomly assigned to be grazed by cattle and three were ungrazed. Grazing was at a rate of one mature cow or equivalent/2.4 ha, from mid-April to early-June in 1971–1973. Elk pellets were counted each spring to assess elk use of plots in winters of 1971–1972, 1972–1973, and 1973–1974.
A replicated, controlled study in 1983–1987 of a rough fescue Festuca scabrella-dominated grassland in Montana, USA (3) found that cattle grazing increased the proportion of rough fescue biomass utilized by elk Cervus canadensis nelsoni in the first, but not second winter after grazing. Over the first winter, a higher proportion of rough fescue was utilized by elk in cattle-grazed plots (58%) than in non-cattle-grazed plots (24%). There was no difference between plots the following winter (cattle grazed: 78%; ungrazed: 69%). Additionally, the proportion of rough fescue plants grazed by elk over the four years from outset of the experiment did not differ between plots grazed (26–98%) or ungrazed (15–97%) by cattle. Cattle-grazing entailed 104 cow/calf pairs on a 104-ha pasture, from 18 October 1983 to 22 December 1983. There were three ungrazed control plots, 2 ha each in extent. Six caged and six non-caged samples on each treatment were clipped in April 1985 and 1986 to determine elk utilization by biomass. Additionally, utilization of rough fescue was assessed by determining the proportion of plants grazed by elk by inspecting the closest plant to 50 points along each of two transects per plot.
A replicated, controlled, before-and-after study in 1998–2000 in five grassland sites in California, USA (4) found that using livestock grazing to manage vegetation had mixed effects on the abundance of Stephens’ kangaroo rat Dipodomys stephensi. One year after grazing started, there was no difference in the density of Stephens’ kangaroo rat (9 animals/ha) compared to before grazing started (9 animals/ha). However, after two years, their density had increased to 22 animals/ha. Areas that were grazed had a lower density of kangaroo rats both before grazing started and after one year when compared to ungrazed areas (9 animals/ha vs 28 animals/ha), but after two years there was no longer a significant difference (22 animals/ha vs 28 animals/ha). In 1998 and 1999, two sites were grazed by sheep for between four hours and three days, and two sites were not grazed in either year. An unspecified number of Sherman live traps were placed in each site. In 1996–2000, at unspecified times of year, trapping was conducted over three consecutive nights. Traps were opened in the evening and checked at midnight and at dawn and animals caught were individually marked.
A replicated, controlled study in 2003–2005 of pasture at a site in northern Norway (5) found that sheep-grazed pasture was used by feeding reindeer Rangifer tarandus more than was ungrazed pasture. Reindeer spent more time feeding in low-intensity sheep grazed plots (30% of all feeding observations) and high-intensity sheep grazed plots (28%) than in ungrazed plots (17%). Sixteen plots were established in each of two 0.3-ha fields. Each field contained four plots of each high-intensity sheep grazing, low-intensity sheep grazing and ungrazed pasture. Low-and high-intensity sheep grazing comprised two (ewe and yearling) and four (ewe and three lambs) sheep respectively, for 10 days at the beginning of July in 2003 and 2004, contained within temporary internal fencing. Four 2-year-old male reindeer were grazed on each field for two weeks in autumn 2003, spring and autumn 2004 and spring 2005. Reindeer feeding patch choice was determined by timed observations.
A replicated, paired sites study in 2014 in 10 pastures in Oaxaca, Mexico (6) found that in pastures grazed by cattle, Tehuantepec jackrabbits Lepus flavigularis spent more time feeding than they did in pastures not grazed by cattle. When in pastures with cattle, Tehuantepec jackrabbits spent more time feeding (75%) than when in pastures without cattle (66%). The study was conducted in five pastures with cattle (average of 16 cows/pasture) and five pastures without. Pastures averaged 11 ha extent and were located next to each other. Cattle moved freely within each pasture. In March 2014, twenty-two adult jackrabbits were captured, radio-tagged and released at the capture site. Animals were followed for ≤10 days in March and September 2014. Additionally, jackrabbit behaviour was recorded from five fixed observation sites throughout the study area. The behaviour (eating, resting and socializing) of jackrabbits was recorded between 6:00–10:00 h and 17:00–20:00 h in pastures with or without cattle.
(1) Anderson E.W. & Scherzinger R.J. (1975) Improving quality of winter forage for elk by cattle grazing. Journal of Range Management, 28, 120–125.
(2) Skovlin J.M., Edgerton P.J. & McConnell B.R. (1983) Elk use of winter range as affected by cattle grazing, fertilizing, and burning in Southeastern Washington. Journal of Range Management, 36, 184–189.
(3) Jourdonnais C.S. & Bedunah D.J. (1990) Prescribed fire and cattle grazing on an elk winter range in Montana. Wildlife Society Bulletin, 18, 232–240.
(4) Kelt D.A., Konno E.S. & Wilson J.A. (2005) Habitat management for the endangered Stephens’ kangaroo rat: the effect of mowing and grazing. The Journal of Wildlife Management, 69, 424–429, https://doi.org/10.2193/0022-541x(2005)069<0424:hmftes>2.0.co;2
(5) Colman J.E., Mysterud A., Jørgensen N.H. & Moe S.R. (2009) Active land use improves reindeer pastures: evidence from a patch choice experiment. Journal of Zoology, 279, 358–363, https://doi.org/10.1111/j.1469-7998.2009.00626.x
(6) Luna-Casanova A., Rioja-Paradela T., Scott-Morales L. & Carrillo-Reyes A. (2016) Endangered jackrabbit Lepus flavigularis prefers to establish its feeding and resting sites on pasture with cattle presence. Therya, 7, 277–284, https://doi.org/10.12933/therya-16-393
13.3. Manage vegetation using grazing by wild herbivores
https://www.conservationevidence.com/actions/2548
- Two studies evaluated the effects on mammals of managing vegetation using grazing by wild herbivores. One study was in the USA1 and one was in South Africa2.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (2 STUDIES)
- Abundance (2 studies): A site comparison study in the USA1 found that areas with higher numbers of wild herbivore grazers hosted more small mammals than did areas grazed by fewer wild herbivores. A study in South Africa2 found that grazing by Cape mountain zebras did not lead to a higher population of bontebok.
BEHAVIOUR (0 STUDIES)
Background
Using grazing to manage vegetation can limit succession that would otherwise lead to an increase in woody plant species. This may help to increase the abundance of mammal species that depend on early-succession habitats. As well as managing vegetation using domestic herbivores, in some cases wild herbivore numbers can be manipulated with similar aims.
A site comparison study in 1998–1999 at a forest site in Tennessee, USA (1) found that in areas grazed by high numbers of wild herbivores, of three species, there were more small mammals than in areas grazed by fewer wild herbivores with just one species present. More small mammals were caught in areas with high wild herbivore abundance (145 small mammals) than in areas with low wild herbivore abundance (96 small mammals). Numbers caught in areas with high and low herbivore abundance were: white-footed mouse Peromyscus leucopus (130 vs 69), northern short-tailed shrew Blarina brevicauda (8 vs 22), woodland vole Microtus pinetorum (2 vs 5), golden mouse Ochrotomys nuttalli (4 vs 0), southern flying squirrel Glaucomys volans (1 vs 0) (species-level results were not statistically tested). Small mammals were surveyed at six plots inside a 324-ha enclosure, where elk Cervus canadensis and bison Bison bison were released in 1994, and six plots outside the enclosure, where no elk or bison occurred. White-tailed deer Odocoileus virginianus occurred both inside and outside the enclosure. Herbivore density was 46/km2 inside the enclosure and 6–10/km2 outside the enclosure. Small mammals were sampled 13 times at each plot, from June 1998 to May 1999, using 15 Sherman live traps, along a 100-m transect, for three nights each time.
A study in 1987–2009 in a shrubland protected area in Western Cape, South Africa (2) found that following the introduction of Cape mountain zebras Equus zebra zebra to manage vegetation and facilitate improved grazing for bontebok Damaliscus pygargus pygargus, numbers of bontebok did not increase. Twenty-two years after Cape mountain zebras were introduced, bontebok numbers were approximately one-third lower (187) than at the time of zebra introduction (298). Authors suggest that zebras and bonteboks may compete for similar resources. In 1987–1990, twelve Cape mountain zebras were translocated into a 3,435-ha national park. Between 1987–1990 and 2009, zebra numbers increased from 12 to 48 individuals. Population monitoring details for bonteboks and zebras are not provided.
(1) Weickert C.C., Whittaker J.C. & Feldhamer G.A. (2001) Effects of enclosed large ungulates on small mammals at Land Between The Lakes, Kentucky. The Canadian Field-Naturalist, 115, 247–250.
(2) Watson L.H., Kraaij T. & Novellie P. (2011) Management of rare ungulates in a small park: habitat use of bontebok and Cape mountain zebra in Bontebok National Park assessed by counts of dung groups. South African Journal of Wildlife Research, 41, 158–166, https://doi.org/10.3957/056.041.0202
13.4. Replant vegetation
https://www.conservationevidence.com/actions/2549
‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.
13.5. Remove vegetation by hand/machine
https://www.conservationevidence.com/actions/2550
- Twenty studies evaluated the effects on mammals of removing vegetation by hand or machine. Eleven studies were in the USA1,3–6,8,9,10,16,18,19, and one each was in Canada2, South Africa15, Israel7, Norway11, Portugal12, France13, Spain14, the Netherlands17 and Thailand20.
COMMUNITY RESPONSE (1 STUDY)
- Richness/diversity (1 study): A site comparison study in the USA3 found that mechanically clearing trees within woodland reduced small mammal diversity.
POPULATION RESPONSE (12 STUDIES)
- Abundance (11 studies): Eight of 11 site comparison or controlled studies (nine of which were replicated), in the USA1,3,4,5,9,10,19, Israel7, Portugal12, Spain14 and the Netherlands17, found that clearing woody vegetation3,5,10,12,14,19 or herbaceous and grassland vegetation4,9 benefitted target mammals. Population or density increases were recorded for small mammals3,5, European rabbits12,14 and Stephens’ kangaroo rat9 while black-tailed prairie dog10 and California ground squirrel19 colonies were larger or denser and Utah prairie dog colonies established better than in uncleared areas4. Two studies found mixed results of clearing woody vegetation, with hazel dormouse abundance declining, then increasing17 and small mammal abundance increasing, then declining in both cleared and uncleared plots alike1. One study found no effect of scrub clearance from sand dunes on habitat specialist small mammals7.
- Survival (1 study): A replicated, site comparison study in the USA16 found that mechanical disturbance of woody vegetation within forest (combined with reseeding, follow-up herbicide application and further seeding) increased overwinter survival of mule deer fawns.
BEHAVIOUR (8 STUDIES)
- Use (8 studies): Four of seven studies (of which six were site comparisons or controlled), in the USA6,8,18, Canada2, Norway11, France13 and Thailand20, found that areas cleared of woody vegetation13,20 or herbaceous and grassland vegetation2,11 were utilized more by mule deer2, reindeer11, mouflon13 and gaur20. One study found that clearing woody vegetation promoted increased use by white-tailed deer in some but not all plots6, one found that it did not increase use by mule deer18 and one found that carrying out a second clearance on previously cleared plots did not increase use by white-tailed deer8. A before-and-after study in South Africa15 found that clearing woody vegetation from shrubland increased wildebeest and zebra abundance following subsequent burning but not when carried out without burning whilst other mammals did not show consistent responses.
Background
Regular disturbance may maintain vegetation in a desirable, semi-natural state — particularly in early-successional habitats. Removal of vegetation may help to maintain habitats in an early-successional state, which may benefit mammal species that depend on such habitats.
This intervention includes removal of annual vegetation (e.g. herbs and grasses removed by mowing) as well as scrubby vegetation and trees. Tree clearance studies included here are those where woodland had colonised previously open areas and was cleared for conservation purposes, without being part of commercial forest management. For studies of partial clearance in long-established or commercially managed forest, see Biological Resource Use — Clear or open patches in forests.
A replicated, controlled, before-and-after study in 1966–1970, of pinyon-juniper woodland and grassland at six sites in Utah, USA (1) found that, after clearance of pinyon-juniper and seeding with grassland species, small mammal abundances in both cleared and uncleared plots followed similar patterns. Comparisons between treatments were not tested for statistical significance. Two years after clearance and seeding, more deer mice Peromyscus maniculatus were caught in cleared plots (107–118 from 180 trap nights) and in uncleared plots (89 from 180 trap nights) than were caught before clearance and seeding (19 from 270 trap nights). However, after three to four years, abundance in cleared plots declined (16–37 mice from 180 trap nights) and abundances in uncleared plots also declined (27–30 from 180 trap nights). Trees were cleared by dragging a heavy chain or were bulldozed. Aerial seeding followed. Felled wood was gathered into lines and left in place or burned, or was dispersed during a second pass of the chain. In 1966–1970, small mammals were sampled using snap-traps over a range of dates in August–November.
A replicated, controlled study in 1975–1977 on grassland in British Columbia, Canada (2) found that in mown areas, bluebunch wheatgrass Agropyron spicatum was consumed more by foraging mule deer Odocoileus hemionus than in unmown areas. Deer took a higher average number of bites/observation of bluebunch wheatgrass in mown plots (12 bites) than in unmown plots (two bites). Plots were studied at two sites in sagebrush and two in Douglas fir Pseudotsuga menziesii forest. At each site, plots (1.25 × 5 m) were established in a block. In each block, in October 1975, three plots were clipped using a lawnmower and electric-powered sickle and three were uncut. In April 1976, three deer were fenced onto the block and their selection between plots was assessed through direct observations at intervals through the day. The same three deer were used on all blocks and observed twice/block for one day each time. In April 1977, four deer were observed, on two blocks combined, over four days.
A site comparison study in 1977 of five areas within a pinyon-juniper woodland in Colorado, USA (3) found that mechanically clearing trees increased small mammal abundance but reduced diversity. More small mammals were caught in area cleared areas (175–295 individuals) than in the uncleared area (102 individuals). However, diversity was lower in cleared areas than in the uncleared area (results reported as Shannon-Weaver diversity index). Small mammals were sampled in four study areas (≤28 km apart). One area was mature pinyon-juniper woodland whilst other areas comprised woodland that had been cleared by chaining (a heavy anchor chain was dragged between two bulldozers) 1, 8, and 15 years previously. Small mammals were live-trapped on three grids in each area (32 trap stations/grid). Trapping was conducted concurrently on all areas, during two trapping sessions of eight days each, in mid-July and mid-August 1977.
A controlled study in 1978–1981 of grassland at four sites in a national park in Utah, USA (4) found that mechanical disturbance of vegetation promoted establishment of translocated Utah prairie dogs Cynomys parvidens. In the first year of translocation, more prairie dogs (8–16) were counted on sites where vegetation was disturbed than on sites where vegetation was not disturbed (0.3). The same pattern held over the second year (disturbed: 9–14; undisturbed: 0 prairie dogs) and third year (disturbed: 15–16; undisturbed: 0 prairie dogs) after translocation. In August 1978, vegetation in one site was disturbed using a rotobeater. In another site, four railroad rails were dragged twice over the site. Vegetation was not disturbed at a third site. Sites were 5 ha each. On each site, 200 artificial burrows were created. In early-summer 1979, a total of 200 prairie-dogs were translocated and released across four sites (these three sites and a fourth site, not detailed here). Counts were conducted through summer and autumn of 1979 and in summer 1980–1981.
A replicated, controlled study in 1981–1983 of a pinyon-juniper woodland in New Mexico, USA (5) found that 13–18 years after treatment, felled or thinned stands had more small mammals than did undisturbed stands. The number of animals caught in stands that were thinned (432) or bulldozed (433) did not differ from each other but both were greater than the number in undisturbed stands (246). Species composition differed, with more grassland species in bulldozed stands (bulldozed: 95–175; thinned: 35; undisturbed: 46) and more woodland mice in thinned stands (thinned: 58; bulldozed: 6–11; undisturbed: 26). Plots, approximately 120 ha each, were established in each of two woodland blocks, one in 1965, one in 1970. In each block, one plot was thinned (trees ≥6.1 m apart), one was bulldozed (trees pushed over and left) and one was undisturbed. Small mammals were trapped in the second and third week of September, each year, in 1981–1983. Each plot was sampled for four days each year.
A randomized, controlled, before-and-after study in 1981–1983 of forest and grassland on a ranch in Texas, USA (6) found that after partial clearing of woody vegetation, there was a mixed response in white-tailed deer Odocoileus virginianus use of these areas. Changes in use of partially cleared areas were not tested for statistical significance. In two of four plots that were partially cleared, average deer numbers increased (after: 22–24 deer/100 ha; before: 3–13 deer/100 ha). In the other two plots that were partially cleared, average deer number declined (after: 11–15 deer/100 ha; before: 13–15 deer/100 ha). In the plot that was not cleared, deer numbers declined (after: 20 deer/100 ha; before: 27 deer/100 ha). On a 20,000 ha ranch, five plots (120 ha each, ≥4 km apart) were studied. Two tractors dragged a heavy-duty chain in a U-shape to partly clear four plots of woody vegetation in May–June 1981. Plots had 30, 50, 70, and 80% of woody vegetation cleared. Uprooted woody material was removed by burning in July 1981. A fifth plot remained uncleared. Treatments were assigned randomly to plots. Deer were counted from helicopter transects, every three months, from March 1981 to March 1983.
A replicated, controlled study in 1995–1996 of a coastal sand dune in Israel (7) found that removing scrub did not increase abundances of habitat specialist sand-living small mammals. The total number of Anderson’s gerbils Gerbillus allenbyi in cleared plots (124) did not significantly differ from that in uncleared plots (107). The same applied for Tristram’s jird Meriones tristrami, (cleared: 3; uncleared: 8). However, scrub clearance reduced numbers of invasive house mice Mus musculus (cleared: 6; uncleared: 109). All aboveground woody vegetation was removed from two 50 × 50-m plots, in September 1995. Plots were >200 m apart. Uncleared plots were located 50–200 m from each cleared plot. Small mammals were surveyed using 36 Sherman live traps in each plot, over four nights, each month, from December 1995 to September 1996.
A before-and-after study in 2001–2002 of a shrubland site in Texas, USA (8) found that carrying out a second mechanical vegetation clearance of plots already subject to an earlier mechanical clearance did not increase their utilization by white-tailed deer Odocoileus virginianus. There was no significant difference in deer track counts between plots before (37 track crossings/km) or after (47 track crossings/km) the second mechanical clearance. Plots (3–9 ha), were established in a 6,154-ha study area. In March–April 1999, five plots were cleared of woody vegetation using a mechanical aerator pulled by a tractor. Plots were mechanically cleared again in September 2000. Deer utilization was assessed by counting tracks along prepared track lanes, over three days on four occasions. Surveys were conducted once before clearance, in late-May to July 2000, and three times after clearance, in December 2000 to January 2001, May 2001 and June–July 2001.
A replicated, controlled, before-and-after study in 1996–2000 of a grassland area in California, USA (9) found that after vegetation mowing commenced, Stephens’ kangaroo rat Dipodomys stephensi abundance increased. More animals were estimated to be in mown plots two years after mowing began (mown: 21; before mowing 18) and in plots that were both mown and grazed (mown: 15; before mowing: 8). Plots that were neither grazed nor mown contained more animals than mown or mown and grazed plots, although the number after management of other plots commenced did not differ from that before management (28 vs 28 kangaroo rats). Seven plots (80 × 80 m) were surveyed. Two were mown in 1998 and 1999, three were mown in 1998 and grazed by sheep in 1999 and two were not grazed or mowed. Mowing cut vegetation as short as the mower allowed. Cut vegetation was left on site. Grazing removed all available forage. Kangaroo rats were surveyed using grids of Sherman live traps, over three consecutive nights, bimonthly, from November 1996 to October 2000.
A replicated, controlled, before-and-after study in 2002–2003 in a national park in Dakota, USA (10) found greater areas occupied by black-tailed prairie dog Cynomys ludovicianus colonies and more prairie dog burrows, in plots that were burned and mechanically cleared of woody vegetation than in plots that were not cleared or burned. The study does not distinguish between the effects of mechanical vegetation clearance and burning. At the end of the second summer after vegetation clearance, prairie dog colonies had expanded more (into 18–70% of available habitat) in burned and cleared plots compared to unmanaged plots (0–5%). In burned and cleared plots, there were more new burrows (191–458) after two summers than in unmanaged plots (41–116). At each of three prairie dog colonies, a 2-ha treatment plot, just beyond the colony boundary, underwent prescribed burning in May 2002 and mechanical removal of woody vegetation in June 2002. Similarly, selected 2-ha plots were left unmanaged. Colonies boundaries were mapped in May–September 2002 and May–August 2003. New burrows were mapped monthly during these periods.
A replicated, controlled study in 2003–2005 of pasture at a site in northern Norway (11) found that mown pasture was selected by feeding reindeer Rangifer tarandus more than was unmown pasture. Reindeer spent more time feeding in mown plots (25% of all feeding observations) than in unmown plots (17%). Sixteen plots were established in each of two 0.3-ha fields. Each field contained four replicate plots of high-intensity sheep grazing, low-intensity sheep grazing, mowing and unmanaged. Sheep grazing treatments are not reported on in the paper. Mown plots were cut in July, to 5 cm height, with cuttings removed. Four 2-year-old male reindeer grazed in each field for two weeks in autumn 2003, spring and autumn 2004 and spring 2005. Reindeer feeding patch choice was determined during timed observations.
A replicated, controlled, before-and-after study in 2000–2002 on scrubland in a nature reserve in southwest Portugal (12) found that clearing scrub (through establishing firebreaks) increased densities of European rabbits Oryctolagus cuniculus. In areas where firebreaks were established average annual rabbit pellet densities (1.1–3.6/m2) were higher than prior to establishment of firebreaks (0.5–1.5/m2). Pellet densities were also higher than in areas where no firebreaks were established (firebreaks: 1.1–3.6/m2; no firebreaks: 0.4–2.2/m2). Four 300-ha sites, ≥3 km apart, were studied. In February 2001, areas of grassland were restored by cutting 5-m-wide firebreak strips through scrub. The other two sites remained unmanaged. Rabbit pellets were counted, monthly, at fixed points along transects, from May 2001 to October 2002.
A controlled study in 2004–2008 of heather moorland at a site in southern France (13) found that cutting heather (Calluna vulgaris and Erica tetralix) resulted in greater use of it by mouflon Ovis gmelini musimon × Ovis sp. Average density of feeding mouflon was higher on cut plots (27/ha) than on uncut plots (5/ha). Prior to the study, each 360 × 80-m plot had not been modified for >40 years. Two plots were cut in spring 2004, to an average height of 5 cm, and two were left uncut. Mouflon use of plots was determined by counting feeding animals in each plot, at 20-minute intervals, for two hours up to sunset. In total, 668 such counts were made in 2004–2008.
A replicated, site comparison study in 2008–2012 in grassland and scrubland along a mountain chain in Andalusia, Spain (14) found that removing scrubland vegetation to create pasture increased abundances of translocated European rabbits Oryctolagus cuniculus in areas of high scrub coverage but not of medium-or low-scrub coverage. In high scrub cover areas, there were more rabbits around plots where scrub was cleared (5.9 latrines/km) than where scrub was not cleared (2.6 latrines/km). There was no significant difference in rabbit abundance in areas of medium cover scrub (scrub clearance: 7.1 pellets/km; no scrub clearance: 5.0 pellets/km) or low scrub cover (scrub clearance: 1.6 pellets/km; no scrub clearance: 2.1 pellets/km). In autumn and winter of 2008–2009, between 75 and 90 rabbits/ha were released into fenced plots (0.5–7.7 ha). Wooden branches and artificial warrens were added within a 500-m radius outside plots and, at some, scrubland was cleared to create pasture (number of plots/treatment and pasture sizes not reported). At the end of each breeding season in 2009–2011, small gates allowed rabbits to disperse through fences into adjacent areas. Rabbit abundance was estimated by latrine counts in four 500-m-long transects around each plot, in summer 2012.
A before-and-after study in 2009–2010 on savannah in South Africa (15) found that in areas cleared of woody vegetation, wildebeest Connochaetes taurinus and zebra Equus burchelli abundance was higher than in uncleared areas after areas were burned, but not before burning, whilst other mammals did not show consistent responses. Wildebeest faecal pellet prevalence was higher in cleared than in uncleared plots after burning (cleared: in 4–7% of plots; uncleared: 1%) but not before (cleared: 0%; uncleared: 2%). Similarly, zebra pellet prevalence was higher in cleared than in uncleared plots after burning (cleared: in 18–30% of plots; uncleared: 7%) but not before (cleared: 16–19%; uncleared: 20%). Impala Aepyceros melampus, kudu Tragelaphus strepsiceros and giraffe Giraffa camelopardalis did not show consistent differences between responses in cleared versus uncleared land. Herbivore abundance was determined by establishing presence or absence of faecal pellets for each species in plots along transects through areas on sandy soils subject to mechanical clearance of woody vegetation by barko crawler, bosvreter and chainsaw (date of clearance not stated) and uncleared areas. Pellets were counted in April–May 2009, prescribed burns were carried out in June–November 2009 and plots were resampled in June 2010.
A replicated, site comparison study in 2005–2008 of a pine-juniper forest in Colorado, USA (16) found that mechanical disturbance of vegetation (combined with reseeding, follow-up herbicide application and further seeding — referred to as advanced management) increased overwinter survival of mule deer Odocoileus hemionus fawns. Management actions were not carried out individually, so their relative effects cannot be determined. Average overwinter survival was highest under advanced management (77%), intermediate under mechanical disturbance and seeding without follow-up actions (69%) and lowest with no habitat management (67%). Mechanical management, commencing in 1998–2004, involved removing and mulching trees to create open areas. These were seeded with grasses and flowering plants. Follow-up actions in advanced management plots, two to four years later, involved controlling weeds with herbicide and further seeding with deer browse species. Fawns were radio-collared on eight study plots; two advanced management plots, four mechanical management plots and two unmanaged plots. Survival was assessed by monitoring fawns from capture (1 December to 1 January) until 15 June, in winters of 2004–2005 through to 2007–2008, three to six years after mechanical treatments.
A replicated, before-and-after, site comparison study in 2009–2013 at six forest sites in the Netherlands (17) found that after clearance of most mature trees, hazel dormouse Muscardinus avellanarius nest abundance declined briefly but then increased relative to areas where no trees were cleared. Dormouse nest numbers in cleared plots fell in the year after clearing to 32% of pre-clearance levels. Two to four years after clearance, nest numbers were higher, at 374–803% of pre-clearance levels. Data were presented as standardised indices. In uncleared plots, there was a declining trend throughout with, at the end of the study, nest numbers 21% of the count made at the start of the study. Dormouse nests were counted along transects in September and November each year in 2009–2013. In 10 arbitrarily chosen ‘managed’ segments along transects (average 92 m long), 75–100% of mature trees were cut in winter 2009–2010. Ten unmanaged transect sections (average 181 m long) were monitored as controls.
A replicated, site comparison study in 2006–2009 of pine and juniper forests interspersed with meadows on a plateau in Colorado, USA (18) found that mule deer Odocoileus hemionus densities did not differ between plots where trees were cleared and those where trees were not cleared. Average deer density was 6–37 deer/km2 on plots where trees were cleared and 5–85 deer/km2 on plots where no trees were cleared. Tree clearance was carried out on four plots, two to eight years prior to deer surveys. This comprised uprooting trees with a bulldozer, followed by mechanical roller chopping to break vegetation into smaller pieces, or hydro-axing, whereby individual trees were mulched to ground level. In two plots, no trees were cleared. Deer numbers were estimated by resighting marked individuals, in late winter each year in 2006–2009, from aerial surveys. Surveys were conducted over 15–94 km2/plot.
A replicated, controlled, paired sites study in 2011–2014 of two areas of grassland and scrubland in southern California, USA (19) found that in mown areas, California ground squirrel Otospermophilus beecheyi burrow densities were higher compared to in unmown areas. Three years after management commenced, there were more squirrel burrows in mown (11–122/subplot) compared to in unmown (12–54/subplot) areas. Each of six plots comprised a circle covering 0.8 ha, divided into three equal wedge-shaped subplots. One subplot in each plot was mown in May, for two years, at 7.5–15 cm height, with cut material removed and one was unmown. (Management details for the third subplot are not relevant to this intervention). Management commenced in 2011 (two plots) and 2012 (four plots). Squirrels were translocated into plots at a target rate of 30–50/plot. Squirrel abundance was determined by counting squirrel burrows.
A site comparison study in 2010–2012 in two secondary forest plots in Nakhon Ratchasima Province, Thailand (20) found that clearing vegetation using chainsaws increased the density of gaur Bos gaurus using these areas. Average gaur density was higher in a plot where pioneer trees were felled (8.6 individuals/km2/day) than in a plot where the vegetation was left unmanaged (4.0 individuals/km2/day). The study was conducted within an 8-km2 area, reforested since 1994. In May–September 2010, a total of 407 pioneer Macaranga siamensis trees were felled with chainsaws to open up 28% of a 5.7-ha plot. Trees were not felled in a nearby 4.7-ha plot. The ground within the felled and unfelled plots was cleared, using a tractor, in June and December 2011. Gaur dung piles were counted monthly, between February 2011 and March 2012, with the exception of June and December 2011. Dung piles were counted by 9–10 volunteers along 50-m-long transects (number not stated) with counts used to estimate guar usage of plots.
(1) Baker M.F. & Frischknecht N.C. (1973) Small mammals increase on recently cleared and seeded juniper rangeland. Journal of Range Management, 26, 101–103.
(2) Willms W., Bailey A.W. & McLean A. (1980) Effect of burning or clipping Agropyron spicatum in the autumn on the spring foraging behaviour of mule deer and cattle. Journal of Applied Ecology, 17, 69–84.
(3) O’Meara T.E., Haufler J.B., Stelter L.H. & Nagy J.G. (1981) Nongame wildlife responses to chaining of pinyon-juniper woodlands. The Journal of Wildlife Management, 45, 381–389.
(4) Player R.L. & Urness P.J. (1982) Habitat manipulation for reestablishment of Utah prairie dogs In Capitol Reef National Park. Great Basin Naturalist, 42, 517–523.
(5) Severson K.E. (1986) Small mammals in modified pinyon-juniper woodlands, New Mexico. Journal of Range Management, 39, 31–34.
(6) Rollins D., Bryant F.C., Waid D.D. & Bradley L.C. (1988) Deer response to brush management in central Texas. Wildlife Society Bulletin, 16, 277–284.
(7) Kutiel P., Peled Y. & Geffen E. (2000) The effect of removing shrub cover on annual plants and small mammals in a coastal sand dune ecosystem. Biological Conservation, 94, 235–242, https://doi.org/10.1016/s0006-3207(99)00172-x
(8) Rogers J.O., Fulbright T.E. & Ruthven D.C. III (2004) Vegetation and deer response to mechanical shrub clearing and burning. Journal of Range Management, 57, 41–48, https://doi.org/10.2307/4003953
(9) Kelt D.A., Konno E.S. & Wilson J.A. (2005) Habitat management for the endangered Stephens’ kangaroo rat: the effect of mowing and grazing. The Journal of Wildlife Management, 69, 424–429, https://doi.org/10.2193/0022-541x(2005)069<0424:hmftes>2.0.co;2
(10) Milne-Laux S. & Sweitzer R.A. (2006) Experimentally induced colony expansion by black-tailed prairie dogs (Cynomys ludovicianus) and implications for conservation. Journal of Mammalogy, 87, 296–303, https://doi.org/10.1644/05-mamm-a-056r2.1
(11) Colman J.E., Mysterud A., Jørgensen N.H. & Moe S.R. (2009) Active land use improves reindeer pastures: evidence from a patch choice experiment. Journal of Zoology, 279, 358–363, https://doi.org/10.1111/j.1469-7998.2009.00626.x
(12) Ferreira C. & Alves P.C. (2009) Influence of habitat management on the abundance and diet of wild rabbit (Oryctolagus cuniculus algirus) populations in Mediterranean ecosystems. European Journal of Wildlife Research, 55, 478–496, https://doi.org/10.1007/s10344-009-0257-4
(13) Cazau M., Garel M. & Maillard D. (2011) Responses of heather moorland and Mediterranean mouflon foraging to prescribed-burning and cutting. The Journal of Wildlife Management, 75, 967–972, https://doi.org/10.1002/jwmg.117
(14) Guerrero-Casado J., Carpio A.J., Ruiz-Aizpurua L. & Tortosa F.S. (2013) Restocking a keystone species in a biodiversity hotspot: Recovering the European rabbit on a landscape scale. Journal for Nature Conservation, 21, 444–448, https://doi.org/10.1016/j.jnc.2013.07.006
(15) Isaacs L., Somers M.J. & Dalerum F. (2013) Effects of prescribed burning and mechanical bush clearing on ungulate space use in an African savannah. Restoration Ecology, 21, 260–266, https://doi.org/10.1111/j.1526-100x.2012.00877.x
(16) Bergman E.J., Bishop C.J., Freddy D.J., White G.C. & Doherty P.F. (2014) Habitat management influences overwinter survival of mule deer fawns in Colorado. The Journal of Wildlife Management, 78, 448–455, https://doi.org/10.1002/jwmg.683
(17) Ramakers J.J.C., Dorenbosch M. & Foppen R.P.B. (2014) Surviving on the edge: a conservation-oriented habitat analysis and forest edge manipulation for the hazel dormouse in the Netherlands. European Journal of Wildlife Research, 60, 927–931, https://doi.org/10.1007/s10344-014-0849-5
(18) Bergman E.J., Doherty P.F., White G.C. & Freddy D.J. (2015) Habitat and herbivore density: response of mule deer to habitat management. The Journal of Wildlife Management, 79, 60–68, https://doi.org/10.1002/jwmg.801
(19) McCullough Hennessy S., Deutschman D.H., Shier D.M., Nordstrom L.A., Lenihan C., Montagne J.-P., Wisinski C.L. & Swaisgood R.R. (2016) Experimental habitat restoration for conserved species using ecosystem engineers and vegetation management. Animal Conservation, 19, 506–514, https://doi.org/10.1111/acv.12266
(20) Prayong N. & Srikosamatara S. (2017) Cutting trees in a secondary forest to increase gaur Bos gaurus numbers in Khao Phaeng Ma Reforestation area, Nakhon Ratchasima Province, Thailand. Conservation Evidence, 14, 5–9.
13.6. Remove vegetation using herbicides
https://www.conservationevidence.com/actions/2565
- Six studies evaluated the effects on mammals of removing vegetation using herbicides. All six studies were in the USA1–6.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (4 STUDIES)
- Abundance (2 studies): Two controlled studies (one replicated) in the USA1,6 found that applying herbicide did not increase numbers of translocated Utah prairie dogs1 or alter mule deer densities in areas of tree clearance6.
- Survival (1 study): A replicated, site comparison study in the USA5 found that applying herbicide, along with mechanical disturbance and seeding, increased overwinter survival of mule deer fawns.
- Condition (1 study): A replicated, controlled study in the USA2 found that applying herbicide did not reduce bot fly infestation rates of rodents and cottontail rabbits.
BEHAVIOUR (2 STUDIES)
- Use (2 studies): Two replicated, controlled studies in the USA3,4 found that applying herbicide increased forest use by female, but not male, white-tailed deer4 and increased pasture use by cottontail rabbits in some, but not all, sampling seasons3.
A controlled study in 1979–1981 at two grassland sites in a national park in Utah, USA (1) found that herbicide application did not increase establishment of translocated Utah prairie dogs Cynomys parvidens. In the first year of translocation, the average number of prairie dogs counted on the site sprayed with herbicide (1.7) was not significantly different to that on the unsprayed site (0.3). In the second and third year, no prairie dogs were counted on either site. One site was treated with the herbicide, 2,4-D, at a rate of 2.2 kg active ingredient/ha (date of treatment not given) and one site was not sprayed. Sites were 5 ha each. On each site, 200 artificial burrows were created. In early-summer 1979, two hundred prairie dogs were translocated and released across four sites (the sprayed and unsprayed sites and two further sites not detailed in this summary). Counts were conducted through summer and fall of 1979 and in summer 1980–1981.
A replicated, controlled study in 1986–1988 of a woodland in Oklahoma, USA (2, same experimental set-up as 3 and 4) found that applying herbicide did not reduce bot fly Cuterebra infestation rates of rodents and cottontail rabbits Sylvilagus floridanus. Prevalence of bot fly did not differ between plots treated with herbicide (present on 64 of 342 animals examined, 19%), or untreated plots (25 of 133 animals examined, 19%). Eight 32.4-ha plots were treated with the herbicides, tebuthiuron or triclopyr (at 2.2 kg/ha), in March or June 1983 and four plots were not sprayed with herbicide. Rodents were collected using snap traps in July–September and December–March during 1986–1988. Cottontail rabbits were collected by shooting in January and July of 1987–1988. Animals were examined for bot fly burden.
A replicated, controlled study in 1986–1988 of forest and grassland at a site in Oklahoma, USA (3, same experimental set-up as 2 and 4) found that herbicide-treated pastures hosted more cottontail rabbits Sylvilagus floridanus than did untreated pastures during some, but not all, sampling seasons. In three of 10 comparisons, cottontails were more abundant in herbicide-treated pastures than in untreated pastures (0.8–1.1 vs 0.1–0.2 rabbits/ha), in two cases they were less abundant on treated than untreated pastures (0.0 vs 1.9 rabbits/ha) and for the other five comparisons no difference was detected. Four 32.4-ha pastures were treated with the herbicides tebuthiuron or triclopyr at a rate of 2.2 kg/ha in March or June 1983 and two were untreated control pastures. Rabbit density was estimated by walking transects three times each July and February, from July 1986 to February 1988.
A randomized, replicated, controlled study in 1988–1989 of an upland hardwood forest with tallgrass prairie in Oklahoma, USA (4 same experimental set-up as 2 and 3) found that applying herbicide increased forest use by female, but not male, white-tailed deer Odocoileus virginianus. Female deer preferentially selected herbicide-treated plots over untreated plots in spring, summer and autumn, but there was no difference in winter. Males showed no preference between treated or untreated plots (see original paper for full results). Four blocks, each consisting of five 32-ha plots, were studied. In each block, the herbicides, tebuthiuron and triclopyr, were sprayed in 1983 in one plot each, as well as in two plots that were also burned each April, in 1985–1987. One plot was not burned or sprayed with herbicide. Two additional pastures that were burned but not sprayed along with adjacent areas that were not burned or sprayed were also monitored. Ten female and seven male deer were radio-tracked, in 1988–1989.
A replicated, site comparison study in 2005–2008 of a pine-juniper forest in Colorado, USA (5) found that herbicide application (combined with seeding and preceded by mechanical disturbance and initial seeding — referred to as advanced management) increased overwinter survival of mule deer Odocoileus hemionus fawns. Management actions were not carried out individually, so their relative effects cannot be determined. Average overwinter survival was highest under advanced management (77%), intermediate under mechanical disturbance and seeding without follow-up actions (69%) and lowest with no habitat management (67%). Mechanical management, commencing in 1998–2004, involved removing and mulching trees to create open areas. These were seeded with grasses and forbs. In advanced management plots, follow-up actions, two to four years later, involved controlling weeds with herbicide and further seeding with deer browse species. Fawns were radio-collared on eight study plots; two advanced management plots, four mechanical management plots and two unmanaged plots. Survival was assessed by monitoring fawns from capture (1 December to 1 January) until 15 June, in winters of 2004–2005 through to 2007–2008, three to six years after mechanical treatments.
A replicated, site comparison study in 2006–2009 in six pine and juniper forest sites in Colorado, USA (6) found that treatment with herbicide, alongside clearance of trees and sowing seed, did not alter mule deer Odocoileus hemionus densities compared to clearance of trees alone. The effects of herbicide and reseeding could not be separated in this study. In areas that were sprayed with herbicide, cleared, and sown with seeds, deer density was not higher (5–31 deer/km2) than in plots that were cleared but not treated with herbicide or sown with seed (6–37 deer/km2). Six sites were cleared of trees, two to eight years before deer surveys, using a bulldozer and by chopping vegetation into smaller pieces, or mulching individual trees to ground level by hydro-axing. On two of these sites, unpalatable grasses were controlled with herbicides and seeds of plant species eaten by mule deer were sown. The four remaining sites were not further managed after tree clearance. Deer numbers were estimated by sighting marked individuals during aerial surveys, in late winter each year of 2006–2009. Areas surveyed were 15–84 km2/site.
(1) Player R.L. & Urness P.J. (1982) Habitat manipulation for reestablishment of Utah prairie dogs In Capitol Reef National Park. Great Basin Naturalist, 42, 517–523.
(2) Boggs J.F., Lochmiller R.L., McMurry S.T., Leslie D.M., & Engle D.M. (1991) Cuterebra infestations in small-mammal communities as influenced by herbicides and fire. Journal of Mammalogy, 72, 322–327.
(3) Lochmiller R.L., Boggs J.F., Mcmurry S.T., Leslie Jr, D.M. & Engle D.M. (1991) Response of cottontail rabbit populations to herbicide and fire applications on cross timbers rangeland. Journal of Range Management, 44, 150–155.
(4) Leslie Jr. D.M., Soper R.B., Lochmiller R.L. & Engle D.M. (1996) Habitat use by white-tailed deer on cross timbers rangeland following brush management. Journal of Range Management, 49, 401–406.
(5) Bergman E.J., Bishop C.J., Freddy D.J., White G.C. & Doherty P.F. (2014) Habitat management influences overwinter survival of mule deer fawns in Colorado. The Journal of Wildlife Management, 78, 448–455, https://doi.org/10.1002/jwmg.683
(6) Bergman E.J., Doherty P.F., White G.C. & Freddy D.J. (2015) Habitat and herbivore density: response of mule deer to habitat management. The Journal of Wildlife Management, 79, 60–68, https://doi.org/10.1002/jwmg.801
13.7. Restore or create grassland
https://www.conservationevidence.com/actions/2566
- Three studies evaluated the effects on mammals of restoring or creating grassland. One study each was in Portugal1, the USA2 and Hungary3.
COMMUNITY RESPONSE (1 STUDY)
- Richness/diversity (1 study): A replicated, site comparison study in Hungary3 found that grassland restored on former cropland hosted a similar small mammal species richness compared to native grassland.
POPULATION RESPONSE (3 STUDIES)
- Abundance (2 studies): A controlled, before-and-after study in Portugal1 found that sowing pasture grasses into areas cleared of scrub did not increase European rabbit densities. A replicated, site comparison study in Hungary3 found that grassland restored on former cropland hosted a similar abundance of small mammals compared to native grassland.
- Survival (1 study): A replicated, site comparison study in the USA2 found that seeding with grassland species as part of a suite of actions including mechanical disturbance and herbicide application increased overwinter survival of mule deer fawns.
BEHAVIOUR (0 STUDIES)
Background
Many grasslands have been lost to agricultural intensification through conversion to cropland or through agricultural abandonment, whereby colonization by woodland or scrub may occur. Agri-environment schemes in Europe and North America support preservation or restoration of grasslands for agricultural, conservation and carbon storage reasons. Restoration of these grasslands may benefit some mammal species that are associated with them.
See also: Restore or create savannas.
A controlled, before-and-after study in 2000–2002 on a scrubland in southwest Portugal (1) found that sowing pasture grasses into areas cleared of scrub did not increase densities of European rabbits Oryctolagus cuniculus. Rabbit pellet density after sowing of seeds (1.6–3.6 pellets/m2) did not differ significantly from that before sowing (1.5 pellets/m2). Trends in rabbit density were similar on an area not sown with seed (after: 1.1–1.3 pellets/m2; before: 0.5 pellets/m2). Two 300-ha study areas were located at least 3 km apart. In February 2001, scrub was cleared in 5-m-wide strips at both sites. Cleared strips at one site were then sown with two pasture grasses, rye Secale cereale and slender oat Avena barbat, and with subterranean clover Trifolium subterraneum. At the second site, no seeds were sown. Rabbit pellets were counted monthly, at fixed points along transects, from May 2001 to October 2002.
A replicated, site comparison study in 2005–2008 of a pine-juniper forest in Colorado, USA (2) found that seeding with grassland species as part of a suite of actions including mechanical disturbance and herbicide application (referred to as advanced management) increased overwinter survival of mule deer Odocoileus hemionus fawns. Average overwinter survival was highest under advanced management (77%), intermediate under mechanical disturbance and reseeding but without follow-up actions (69%) and lowest with no habitat management (67%). Mechanical management, commencing in 1998–2004, involved removing and mulching trees to create open areas. These were reseeded with grasses and other flowering plants. Follow-up actions in advanced management plots, two to four years later, involved controlling weeds with herbicide and further seeding with deer browse species. Management actions were not carried out individually, so their relative effects cannot be determined. Fawns were radio-collared on eight study plots; two advanced management plots, four mechanical management plots and two unmanaged plots. Survival was assessed by monitoring fawns from capture (1 December to 1 January) until 15 June, in winters of 2004–2005 to 2007–2008, three to six years after mechanical treatments.
A replicated, site comparison study in 2011–2012 in a marsh and grassland site in Hungary (3) found that grassland restored on former cropland hosted a similar species richness and abundance of small mammals compared to native grassland. The average species richness in restored grassland plots (0–5.9/survey) did not differ significantly from native grassland (0–6.0/survey). Likewise, the average total small mammal catch did not differ between restored grassland (0–40/survey) and native grassland (0–48/survey). However, among restored plots, June-mown restorations had more individuals (1–40/survey) than did August-mown (0–17/survey) or sheep-grazed (0–9/survey) restorations. Restoration was carried out in 2005–2008 on former cropland. Within a 4,073-ha site, eight restored grassland plots and two natural grassland plots were studied. Plots covered 16–300 ha. Small mammals were surveyed using 36 Sherman live traps/site, over five nights and days, in spring and autumn of 2011 and 2012.
(1) Ferreira C. & Alves P.C. (2009) Influence of habitat management on the abundance and diet of wild rabbit (Oryctolagus cuniculus algirus) populations in Mediterranean ecosystems. European Journal of Wildlife Research, 55, 478–496, https://doi.org/10.1007/s10344-009-0257-4
(2) Bergman E.J., Bishop C.J., Freddy D.J., White G.C. & Doherty P.F. (2014) Habitat management influences overwinter survival of mule deer fawns in Colorado. The Journal of Wildlife Management, 78, 448–455, https://doi.org/10.1002/jwmg.683
(3) Mérő T.O., Bocz R., Polyák L., Horváth G. & Lengyel S. (2015) Local habitat management and landscape-scale restoration influence small-mammal communities in grasslands. Animal Conservation, 18, 442–450, https://doi.org/10.1111/acv.12191
13.8. Restore or create savannas
https://www.conservationevidence.com/actions/2568
- Two studies evaluated the effects on mammals of restoring or creating savannas. One study was in Senegal1 and one was in the USA2.
COMMUNITY RESPONSE (1 STUDY)
- Richness/diversity (1 study): A replicated, randomized, paired sites, controlled study in the USA2 found that restoring savannas by removing trees increased small mammal diversity.
POPULATION RESPONSE (2 STUDIES)
- Abundance (2 studies): A study in Senegal1 found that in a population of dorcas gazelle translocated into a fenced enclosure where vegetation had been restored, births outnumbered deaths. A replicated, randomized, paired sites, controlled study in the USA2 found that restoring savannas by removing trees did not, in most cases, change small mammal abundance.
BEHAVIOUR (0 STUDIES)
A study in 2009–2013 in a savanna site in Katané, Senegal (1) found that in a population of dorcas gazelle Gazella dorcas neglecta translocated into a fenced enclosure where vegetation had been restored, births outnumbered deaths. It is not clear whether these effects were a direct result of vegetation restoration or translocation into a fenced area. Over four years after release, more births (31) than deaths (4) of dorcas gazelles were recorded. Twenty-three (nine male and 14 female) dorcas gazelles were translocated between two reserves in northern Senegal in March 2009. Vegetation was restored prior to the translocation but no details regarding the restoration are provided. Gazelles were released into a 440-ha fenced enclosure that was enlarged to 640 ha in 2010. The translocated dorcas gazelles shared the enclosure with scimitar-horned oryx Oryx dammah, mhorr gazelle Nanger dama mhorr and red-fronted gazelle Eudorcas rufifrons. The enclosure fence was not impermeable to small-to-medium sized animals, including predators. Dorcas gazelles were ear-tagged and monitored from June 2009 to March 2013.
A replicated, randomized, paired sites, controlled study in 2008–2013 in five areas in a former oak savanna in Michigan, USA (2) found that restoring savannas by removing trees resulted in no change in small mammal abundance in 18 of 21 comparisons, but that small mammal diversity increased. After five years, in 18 of 21 comparisons small mammal abundance did not differ between areas where trees were removed (0.0–4.2 animals/area) and areas where trees were retained (0.0–0.6 animals/area). However, in three of 21 comparisons there were more small mammals (trees removed: 1.8–4.6 animals/area; trees retained: 0.0–1.8 animals/area). Small mammal diversity increased where trees were removed, but it declined where trees were retained (data reported as model results). In June–July 2008, five 3.2-ha blocks, each comprising four 0.8-ha plots, were designated. In each block, trees were removed from three plots and retained in one plot. In July 2010 the entire area was burnt in a prescribed burn. Once a year, in October 2008–July 2013, nine live traps baited with sunflower seeds were placed in each plot. Traps were set at 17:00–20:00 and checked at 6:00–11:00. Captured animals were individually marked to enable identification of re-captures.
(1) Abáigar T., Cano M., Djigo C.A., Gomis J., Sarr T., Youm B., Fernández-Bellon H. & Ensenyat C. (2016) Social organization and demography of reintroduced Dorcas gazelle (Gazella dorcas neglecta) in North Ferlo Fauna Reserve, Senegal. Mammalia, 80, 593–600, https://doi.org/10.1515/mammalia-2015-0017
(2) Larsen A.L., Jacquot J.J., Keenlance P.W. & Keough H.L. (2016) Effects of an ongoing oak savanna restoration on small mammals in Lower Michigan. Forest Ecology and Management, 367, 120–127, https://doi.org/10.1016/j.foreco.2016.02.016
13.9. Restore or create shrubland
https://www.conservationevidence.com/actions/2569
- Three studies evaluated the effects on mammals of restoring or creating shrubland. Two studies were in the USA1,3 and one was in Mexico2.
COMMUNITY RESPONSE (2 STUDIES)
- Richness/diversity (2 studies): Two site comparison studies, in the USA1 and Mexico2, found that following desert scrub1 or shrubland2 restoration, mammal species richness was similar to that in undisturbed areas.
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): A site comparison study in the USA1 found that restored desert scrub hosted similar small mammal abundance compared to undisturbed desert scrub.
BEHAVIOUR (1 STUDY)
- Use (1 study): A replicated, site comparison study in the USA3 found that restoring shrubland following tree clearance did not increase usage of areas by mule deer compared to tree clearance alone.
Background
Loss of shrubland may be due to a range of factors, including too many grazing animals inhibiting regeneration of shrubs, too few grazing animals or fire suppression leading to reversion to woodland, or invasion by non-native species. Shrubland restoration or creation may benefit mammals associated with the habitat.
A site comparison study in 1995 in a desert site in California, USA (1) found that restored desert scrub hosted similar small mammal species richness and abundance compared to undisturbed desert scrub. Five small mammal species were recorded in restored desert scrub, similar to the seven recorded in undisturbed desert scrub. Additionally, the average number of individuals caught of each species did not differ significantly between restored and undisturbed desert scrub (San Diego pocket mouse Chaetodipus fallax: 2.9 vs 3.5 individuals/night; spiny pocket mouse Chaetodipus spinatus: 2.9 vs 1.4; Merriam’s kangaroo rat Dipodomys merriami: 0.0 vs 0.1; desert woodrat Neotoma lepida: 7.4 vs 8.0; cactus mouse Peromyscus eremicus: 5.8 vs 3.4; deer mouse Peromyscus maniculatus: 4.5 vs 2.8; California ground squirrel Spermophilus beecheyi: 0.0 vs 0.1). Small mammals were caught in a 20-acre desert scrub site restored after construction of a dam, and in surrounding undisturbed desert scrub. During eight nights in March–May 1995, small mammals were captured with 180 Sherman live traps, divided equally between restored and undisturbed desert scrub. Traps were set in different locations each trap-night. Desert scrub was restored by topsoil replacement, direct seeding of shrubs and planting of shrub seedlings.
A site comparison study in 2009–2010 of scrubland at three sites in Mexico City, Mexico (2) found that where native shrubland vegetation was restored on degraded areas, mammal species richness was similar to that in a natural area, but more species were non-native. No statistical analyses were performed. In restored areas mammal species richness was similar (8–10 species) to that in an undisturbed shrubland (7 species). However, the restored areas had more non-native species (4 species) than did the undisturbed area (1 species). In 2005–2006, in two sites, non-native plants were removed and native shrubland vegetation was established. A nearby undisturbed shrubland was used for comparison. Small mammals were surveyed using 16 Sherman live traps on each site, over two consecutive nights, every three months, from February 2009 to May 2010. Medium-sized mammals were surveyed on day and night visits, every two weeks, from May 2009 to May 2010. Mammal latrine samples were identified to species.
A replicated, site comparison study in 2006–2009 of pine and juniper forests interspersed with grassland in Colorado, USA (3) found that restoring shrubland by sowing seeds and applying herbicide following tree clearance, did not increase densities of mule deer Odocoileus hemionus using these plots compared to plots that were cleared of trees alone. The effects of seeding and herbicide could not be separated in this study. Deer densities in cleared plots that were seeded and sprayed with herbicide (5–31 deer/km2) were not significantly different from those in plots that were just cleared (6–37 deer/km2). Six plots were cleared of trees, 2–8 years before deer surveys commenced, using a bulldozer and by chopping vegetation, or mulching trees to ground level, by hydro-axing. On two plots, at the same time as deer surveys, unpalatable grasses were controlled with herbicides and seeds, mainly of shrub species eaten by mule deer, were sown. The four remaining plots were not further managed after tree clearance. Deer numbers were estimated by sighting marked individuals during aerial surveys, in late winter each year, in 2006–2009 (not all plots were surveyed each year). Areas surveyed were 15–84 km2/plot.
(1) Patten M.A. (1997) Reestablishment of a rodent community in restored desert scrub. Restoration Ecology, 5, 156–161.
(2) San-José M., Garmendia A. & Cano-Santana Z. (2013) Vertebrate fauna evaluation after habitat restoration in a reserve within Mexico City. Ecological Restoration, 31, 249–252, https://doi.org/10.3368/er.31.3.249
(3) Bergman E.J., Doherty P.F., White G.C. & Freddy D.J. (2015) Habitat and herbivore density: response of mule deer to habitat management. The Journal of Wildlife Management, 79, 60–68, https://doi.org/10.1002/jwmg.801
13.10. Restore or create forest
https://www.conservationevidence.com/actions/2570
- Five studies evaluated the effects on mammals of restoring or creating forest. Two studies were in the USA1,2 and one each were in Colombia3, Italy4 and Australia5.
COMMUNITY RESPONSE (2 STUDIES)
- Richness/diversity (2 studies): Two site comparison studies (one replicated) in the USA1 and Colombia3 found that mammal species richness in restored forest was similar to that in established forest.
POPULATION RESPONSE (2 STUDIES)
- Abundance (2 studies): One of two replicated studies (one a site comparison) in Australia5 and Italy4 found that replanted or regrowing forest supported a higher abundance of hazel dormice than did coppiced forest4. The other study found only low numbers of common brushtail possums or common ringtail possums by 7–30 years after planting5.
BEHAVIOUR (1 STUDY)
- Usage (1 study): A replicated, site comparison study in the USA2 found that restored riparian forest areas were visited more by carnivores than were remnant forests when restored areas were newly established, but not subsequently, whilst restored areas were not visited more frequently by black-tailed deer.
Background
Restoring or creating forest and woodland may provide important habitat for forest-dependant mammal species, particularly in disturbed or fragmented landscapes. Trees grow slowly and therefore the effects of forest restoration may not be evident for decades or even longer after restoration begins. Care must therefore be taken when interpreting the results of these studies.
A replicated, site comparison study in 1999–2001 of riparian forest at a site in California, USA (1) found that mammal species richness in restored riparian forest was similar to that in natural riparian forest. Mammal species richness in restored sites did not differ from that in natural sites during any season of sampling (data not reported). There was also no significant difference in species richness of small mammals (rodents and shrews) between restored (2–3 species) and natural (3–5 species) sites. Restoration, which included planting of woody riparian species, commenced between 1996 and 1998. Small mammals were surveyed between December 1999 and February 2001, using 16 Sherman live traps/ha. Other mammals were caught in larger live traps (cross section 7.6 × 8.9 cm) between November 1999 and April 2001.
A replicated, site comparison study in 2010–2012 of 16 riparian forest sites in California, USA (2) found that restored riparian forest areas were visited more by carnivores than were remnant forests when restored areas were newly established, but not subsequently, whilst restored areas were not visited more frequently by black-tailed deer Odocoileus hemionus columbianus. More mammalian carnivore species were detected in young restored forests (3.4/plot) than in remnant forests (1.8/plot) but neither figure differed from that in old restored forests (2.1/plot). Coyotes Canis latrans made more visits to young restored forests than to remnant forests (data not presented). No differences were detected between visit rates to the three forest stages for raccoon Procyon lotor, bobcat Felis rufus or black-tailed deer. Five young restored forests (restored in 2003–2007), six old restored forests (restored in 1991–2001) and five natural forest remnants were sampled. Camera traps were operated over two consecutive years in December–March and May–July, starting in December 2010 and finishing in July 2012.
A site comparison study in 2013–2014 in a forest in Caldas department, Colombia (3) found that mammal species richness was similar in an area reforested with flooded gum Eucalyptus grandis compared to native forest, though there were differences in occurrence rates of individual species between forest types. Mammal species richness did not differ significantly between the reforested (9 species) and native forest (11 species) areas. Nine-banded armadillos Dasypus novemcinctus were recorded less frequently in the reforested site (10 records) than in native forest (30 records) as were South American coatis Nasua nasua (23 vs 48 records). Western mountain coatis Nasuella olivacea was recorded more frequently (43 records) in the reforested site than in native forest (10 records). There were no differences in the number of records of red-tailed squirrel Sciurus granatensis or dwarf red brocket Mazama rufina between forest types (data not reported). A 93-ha area, reforested in the 1960s, was compared with a 146-ha native forest block. Mammals were surveyed using four camera traps each in the two forest blocks, from September 2013 to February 2014.
A replicated study in 2010–2012 of 10 deciduous woodland sites in a protected area in central Italy (4) found that forest regrowing on previously cultivated and/or grazed land had a greater abundance of hazel dormice Muscardinus avellanarius, and they had greater survival rates, than in coppiced forest. Peak abundance was higher in regrowing forest plots (17 dormice/plot) than in recent coppice (0–1/plot) and old coppice (1–7/plot). Monthly survival probability in regrowing forest (0.75) was higher than in old coppice (0.43). Too few dormice were recorded in young coppice to calculate survival. Forest type did not affect average litter size (regrowing forest: 4.5 young/litter; old coppice: 4.8 young/litter; no litters found in new coppice). Hazel dormice were surveyed within a grid of 36 tree-mounted wooden nest boxes/plot. Two recently coppiced plots (1–5 years since coppicing), three old coppice plots (20–30 years since coppicing) and two regrowing plots (formerly cultivated and/or grazed areas, unmanaged for 20 years) were sampled.
A replicated, site comparison study in 2002–2011 of 137 forest sites in New South Wales, Australia (5) found that replanted forest supported few common brushtail possums Trichosurus vulpecula or common ringtail possums Pseudocheirus peregrinus by 7–30 years after planting. The probability of a replanted site holding brushtail possums when surveyed 7–30 years after planting (0.02) was lower than that in old growth forest (0.44). For ringtail possums, the probability of occupancy in replanted forest 7–30 years after planting (0.07) was also lower than that in old growth forest (0.75). Greater tree cover in the surrounding area did not increase the probability of subsequent colonisation for either species (result presented as model coefficient). Sixty-five replanted forests and 72 old growth forests were surveyed. Most replanted forests were 7–30 years old and comprised local and exotic Australian plant species. Old growth forests were ≥200 years old. Marsupials were surveyed by spotlight, whilst walking at an average 3 km/h, 1–5 hours after dusk. At each site a 200-m transect was surveyed for 20 min. Sites were surveyed in winter 2002, 2003, 2008, 2009 and 2011.
(1) Queheillalt D.M. & Morrison M.L. (2006) Vertebrate use of a restored riparian site: a case study on the central coast of California. The Journal of Wildlife Management, 70, 859–866, https://doi.org/10.2193/0022-541x(2006)70[859:vuoarr]2.0.co;2
(2) Derugin V.V., Silveira J.G., Golet G.H. & LeBuhn G. (2016) Response of medium-and large-sized terrestrial fauna to corridor restoration along the middle Sacramento River. Restoration Ecology, 24, 128–136, https://doi.org/10.1111/rec.12286
(3) Ramírez-Mejía A.F. & Sánchez F. (2016) Activity patterns and habitat use of mammals in an Andean forest and a Eucalyptus reforestation in Colombia. Hystrix, 27, 11319.
(4) Sozio G., Iannarilli F., Melcorea I., Boschetti M., Fipaldini D., Luciani M., Roviani D., Schiavano A. & Mortelliti A. (2016) Forest management affects individual and population parameters of the hazel dormouse Muscardinus avellanarius. Mammalian Biology, 81, 96–103, https://doi.org/10.1016/j.mambio.2014.12.006
(5) Lindenmayer D.B., Mortelliti A., Ikin K., Pierson J., Crane M., Michael D. & Okada S. (2017) The vacant planting: limited influence of habitat restoration on patch colonization patterns by arboreal marsupials in south-eastern Australia. Animal Conservation, 20, 294–304, https://doi.org/10.1111/acv.12316
13.11. Restore or create wetlands
https://www.conservationevidence.com/actions/2572
- Four studies evaluated the effects on mammals of restoring or creating wetlands. Three studies were in the USA1,2,3 and one was in the UK4.
COMMUNITY RESPONSE (2 STUDIES)
- Community composition (1 study): A site comparison study in the USA2 found that the composition of mammal species present differed between a created and a natural wetland.
- Richness/diversity (2 studies): Two site comparison studies (one replicated) in the USA2,3, found that mammal species richness did not differ between created and natural wetlands2,3.
POPULATION RESPONSE (2 STUDIES)
- Abundance (1 study): A before-and-after study in the USA1 found that following marshland restoration, muskrat abundance increased.
- Survival (1 study): A replicated, controlled, before-and-after study in the UK4, found that water voles persisted better in wetlands that were partially restored using mechanical or manual methods than they did in wetlands undergoing complete mechanical restoration.
BEHAVIOUR (0 STUDIES)
Background
Wetland habitats are often drained or degraded during the development of agriculture or expansion of urban areas or other land uses. Restoration of these wetland habitats can help to increase local species richness and abundance of mammal species that depend on wetlands.
A before-and-after study from the 1960s to 1981 of a marshland alongside Lake Erie, Ohio, USA (1) found that marshland restoration was associated with increased numbers of muskrat Ondatra zibethicus. Population trends were not tested statistically. Four to five years after marsh restoration started, the average number of muskrat pelts collected in the annual harvest (3,657–5,583) was higher than four years prior to restoration (376). The number of pelts was similar to that 10 years prior to restoration, before the marshland was degraded by high water levels (3,681 pelts). Muskrat pelt prices did not significantly affect harvest size. Marsh was restored by reconstructing dikes to facilitate water level control. Muskrat harvest figures were obtained from trappers, who traditionally trapped the same areas each year. The harvest was not directly regulated.
A site comparison study in 1994–1995 of two forested wetlands in Maryland, USA (2) found that a created forested wetland had the same mammal species richness as a nearby natural site, but different species composition. No statistical analyses were performed. Four mammal species were recorded both on the created site and the natural site. Meadow vole Microtus pennsylvanicus was more abundant at the created site (0.17–0.58 individuals/trap/day) than at the natural site (0 individuals/trap/day). The same pattern was seen for House mouse Mus musculus, and domestic cat Felis catus (no data reported). White-footed mouse Peromyscus leucopus was less abundant at the created site (0–0.17 individuals/trap/night) than at the natural site (0.14–0.67 individuals/trap/night). Pine vole Pitymys pinetorum, gray squirrel Sciurus carolinensis and opossum Didelphis virginiana were found only in the natural site. Forest wetland (5.5 ha) was created on a former firing range. The site was graded in December 1993 and planted with native vegetation in spring and summer 1994. Mammals were live-trapped from November 1994 to March 1995 on the created site and adjacent natural forest wetland, using Sherman traps and larger box traps. Tracks were monitored in sand pits in summer 1995.
A replicated, site comparison study in 1999–2000 of 17 wetlands in South Dakota, USA (3) found that mammal species richness was similar in created, restored and enhanced wetlands compared to in natural wetlands. There was no significant difference in the average number of species found in created (2.7 species), restored (2.4 species) and enhanced wetlands (1.9 species) and in natural wetlands (1.4 species). Four created, four restored, four enhanced and five natural wetlands were sampled. Wetland creation involved either impounding a small stream or excavating a basin. Restoration included plugging drainage ditches or breaking sub-surface drainage tiles. Enhancement included manipulating water levels to increase wetland size or changing vegetation structure. Wetland creation, restoration and enhancement was carried out within the previous 10 years. Monitoring was undertaken in spring and autumn in 1999–2000. Sampling at each site included live-trapping (four transects, each with five traps spaced 5 m apart), complemented with pitfall traps and sightings.
A replicated, controlled, before-and-after study in 2008–2010 on a wetland near Peterborough, UK (4), found that partial pond restoration using mechanical or manual methods led to greater persistence of water voles Arvicola amphibius than did complete mechanical restoration. No statistical analyses were performed. After management, the number of pond visits (out of 12: four visits to each of three ponds) revealing water vole presence at partial manual restoration ponds (nine) and partial mechanical restoration ponds (nine) was greater than at full mechanical restoration ponds (two) and similar to that at unmanaged ponds (10). Before management, water voles were present at all ponds set to undergo restoration and at two of three unmanaged ponds. Pond restoration took place between October 2008 and January 2009, on a 126-ha site. Four ponds were restored by complete mechanical excavation of edge and bottom vegetation, four by mechanical clearance of 15 m of pond edge, four by manual clearance of 15 m of pond edge and four were unmanaged. Ponds were in three replicate clusters. Monitoring entailed searches for water vole feeding signs or latrines in autumn 2008 (pre-restoration) and in June, September and October 2009 and March 2010 (post-restoration).
(1) Kroll R.W. & Meeks R.L. (1985) Muskrat population recovery following habitat re-establishment near Southwestern Lake Erie. Wildlife Society Bulletin, 13, 483–486.
(2) Perry M.C., Sibrel C.B. & Gough G.A. (1996) Wetlands mitigation: partnership between an electric power company and a federal wildlife refuge. Environmental Management, 20, 933–939.
(3) Juni S. & Berry C.R. (2001) A biodiversity assessment of compensatory mitigation wetlands in eastern South Dakota. Proceedings of the South Dakota Academy of Science, 80, 185–200
(4) Furnborough P., Kirby P., Lambert S., Pankhurst T., Parker P. & Piec D. (2011) The effectiveness and cost efficiency of different pond restoration techniques for bearded stonewort and other aquatic taxa. Report on the Second Life for Ponds project at Hampton Nature Reserve in Peterborough, Cambridgeshire. The Froglife Trust, Peterborough, UK.
13.12. Manage wetland water levels for mammal species
https://www.conservationevidence.com/actions/2574
- One study evaluated the effects of managing wetland water levels for mammal species. This study was in the USA1.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): A replicated, site comparison study in the USA1 found that managing wetland water levels to be higher in winter increased the abundance of muskrat houses.
BEHAVIOUR (0 STUDIES)
Background
Some wetland mammal species may benefit from specific management of water levels. Water levels may affect factors such as predation rates, food availability and access to shelter. Management of wetland levels will affect a range of wetland species, so decisions regarding such management should be taken with regard to this full assemblage where possible.
A replicated, site comparison study in 2000–2006 at three wetland sites on the St Lawrence River, USA (1) found that managing wetland water levels to be higher in winter increased the abundance of muskrat Ondatra zibethicus houses. This result was not analysed for statistical significance. At wetlands where water levels were managed to be higher in winter, muskrat house density was higher (3.0 houses/ha) than in wetlands where water levels were not managed (0.7 houses/ha). At two wetland sites, in 2000–2004 and 2004–2006, water control structures were installed to increase water levels during winter. At a third site, no such structure was installed. Where water levels were not managed, they were lower during winter. Muskrat houses were counted at all sites in winters of 2001–2006, using unspecified methodologies.
(1) Toner J., Farrell J.M. & Mead J.V. (2010) Muskrat abundance responses to water level regulation within freshwater coastal wetlands. Wetlands, 30, 211–219, https://doi.org/10.1007/s13157-010-0034-x
13.13. Create or maintain corridors between habitat patches
https://www.conservationevidence.com/actions/2576
- Four studies evaluated the effects on mammals of creating or maintaining corridors between habitat patches. One study was in each of Canada1, the USA2, Norway3 and the Czech Republic4.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (0 STUDIES)
BEHAVIOUR (4 STUDIES)
- Use (4 studies): Four studies (three replicated) in Canada1, the USA2, Norway3 and the Czech Republic4 found that corridors between habitat patches were used by small mammals1,2,3,4. Additionally, North American deermice moved further through corridors with increased corridor width and connectivity2 and root voles moved further in corridors of intermediate width3.
Background
Corridors are areas of natural habitat that are contiguous or isolated (i.e. linkages or stepping stones; Rouget et al. 2006). They may enable animals to disperse and migrate between intact habitat patches, which may increase their chances of survival. They may be particularly important in landscapes where there is relatively little remaining natural habitat.
Rouget M., Cowling R.M., Lombard A.T., Knight A.T. & Kerley G.I.H. (2006) Designing large-scale conservation corridors for pattern and process. Conservation Biology, 20, 549–561.
A replicated, site comparison study in 1989 of woodland blocks and connecting woodland and grassland corridors at a site in Ontario, Canada (1) found that wooded corridors were used by both resident and transient eastern chipmunks Tamias striatus. In total there were 530 captures of 119 chipmunks (68 males, 51 females). Chipmunks were resident (caught in >1 trapping session) in all four woods and were trapped in 14 of the 18 corridors. They were trapped in all 13 corridors that were characterised by mature trees. Just one was caught among the five grass-dominated corridors that largely lacked trees or shrubs. Chipmunks were live-trapped in four woods and 18 corridors across 220 ha of farmland (mostly pasture and crops). Corridors were field margins alongside fences with vegetation ranging from long grass, through shrubs to mature woodland trees. Four trapping sessions were conducted in May–September 1989. Each session comprised four consecutive days trapping in woods and, the following week, four consecutive days trapping in corridors.
A randomized, replicated study in 1992 of woodland corridors in a national park in Wyoming, USA (2) found that increased corridor continuity and greater corridor width increased movements of North American deermice Peromyscus maniculatus. Travel along corridors by deermice was greater in continuous corridors than those with gaps and was greater in wide than narrow corridors. However, vegetation characteristics (tree density, ground cover and fallen log density) were more important in determining deermouse movements (results presented as statistical model). Twelve corridors were studied, these being linear stands of aspen Populus tremuloides, surrounded by sagebrush Artemesia sp. Three corridors were wide (20–27 m) with a 10-m gap part-way along, three were wide and continuous, three were narrow (10–16 m) with a 10-m gap and three were narrow and continuous. Deermice were monitored by live-trapping over 10 days, in May–July 1992, at each side of gaps and equivalent spacing in continuous corridors.
A replicated study in 1992 of a grassland in southeast Norway (3) found that root voles Microtus oeconomus used habitat corridors, but moved further in intermediate-width than in narrow or wide corridors. In intermediate (1-m-wide) corridors, voles moved an average of 205 m along the corridor in 12 hours. In narrow (0.4-m-wide) corridors, average movement was 35 m and, in wide (3 m-wide) corridors, was 75 m. Two 5 × 5-m habitat patches were connected by a 310 m-long corridor. Patches and corridor comprised dense, homogeneous meadow vegetation. Adult male voles were released, one in each habitat patch, at 08:00 h and the trial was terminated at 18:00 h. Fieldwork spanned August–October 1992, starting with the wide corridor. Corridor width was then reduced by mowing and herbicide use. Vole movements were monitored by radio tracking and footprint plates.
A site comparison study in 1992–1996 in an agricultural landscape in Moravia, Czech Republic (4) found that corridors created between habitat patches were used by eight small mammal species. Eight small mammal species were recorded in the corridor, five of which were also present in a nearby native woodland. In 1991, native trees and shrubs were planted in agricultural fields to create a 10-m-wide corridor. To survey small mammal populations in the corridor, 100 snap-traps were placed at 3-m intervals, and 50 snap-traps were placed in a nearby forest. Each trap was baited with a wick soaked in fat and left for three nights. Traps were set twice each year, in spring and autumn, in 1992–1996, apart from in 1994, when sampling was also carried out in summer.
(1) Bennett A.F., Henein K. & Merriam G. (1994) Corridor use and the elements of corridor quality: chipmunks and fencerows in a farmland mosaic. Biological Conservation, 68, 155–165.
(2) Ruefenacht B. & Knight R.L. (1995) Influences of corridor continuity and width on survival and movement of deermice. Biological Conservation, 71, 269–274.
(3) Andreassen H.P., Halle S. & Ims R.A. (1996) Optimal width of movement corridors for root voles: not too narrow and not too wide. Journal of Applied Ecology, 33, 63–70.
(4) Bryja J. & Zukal J. (2000) Small mammal communities in newly planted biocorridors and their surroundings in southern Moravia (Czech Republic). Folia Zoologica-Praha, 49, 191–197.
13.14. Apply fertilizer to vegetation to increase food availability
https://www.conservationevidence.com/actions/2577
- Two studies evaluated the effects on mammals of applying fertilizer to vegetation to increase food availability. One study was in Canada1 and one was in the USA2.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (0 STUDIES)
BEHAVIOUR (2 STUDIES)
- Use (2 studies): Two replicated, controlled studies, in Canada1 and the USA2, found that applying fertilizer increased the use of vegetation by pronghorns1 and Rocky Mountain elk2.
A replicated, controlled study in 1977 on a sagebrush grassland site in Alberta, Canada (1) found that fertilizing sagebrush increased its usage by pronghorns Antilocapra americana. There were 21% more pronghorn faecal pellets on fertilized sagebrush than on unfertilized sagebrush (counts not presented). The proportion of sagebrush leaders browsed by proghorns in fertilized plots (34%) was higher than in unfertilized plots (18%). Twenty-two pronghorns were retained in a 256-ha enclosure from April 1975 to November 1977. Twelve plots, each 6 × 15 m, were fertilized, with 84–252 kg N/ha and 39–118 kg P/ha, on 29 April 1975. For each plot, two unfertilized control plots were established. In November 1977, pronghorn use of plots was assessed by faecal pellet counts and by assessing the proportion of sagebrush leaders that was browsed.
A randomized, replicated, controlled study in 1971–1974 of a grassland in Washington, USA (2) found that applying fertilizer increased overwintering numbers of Rocky Mountain elk Cervus canadensis nelsoni the following winter, but not in subsequent winters. After one year, elk use was higher in fertilized areas (82 elk days/ha) than in unfertilized areas (55 elk days/ha). There was no difference in use by elk in the second (fertilized: 79; unfertilized: 90 elk days/ha) or third winters (fertilized: 45; unfertilized: 42 elk days/ha) following fertilizer application. Within each of six plots, one subplot was randomly assigned for fertilizer application and one was unfertilized. Subplots measured 3 ha. Fertilizer was applied once, in autumn 1971, at 56 kg N/ha. Elk pellets were counted in spring, to assess use of plots in the winters of 1971–1972, 1972–1973 and 1973–1974.
(1) Barrett M.W. (1979) Evaluation of fertilizer on pronghorn winter range in Alberta. Journal of Range Management, 32, 55–59.
(2) Skovlin J.M., Edgerton P.J. & McConnell B.R. (1983) Elk use of winter range as affected by cattle grazing, fertilizing, and burning in Southeastern Washington. Journal of Range Management, 36, 184–189.
13.15. Provide artificial refuges/breeding sites
https://www.conservationevidence.com/actions/2583
- Eight studies evaluated the effects on mammals of providing artificial refuges/breeding sites. Two studies were in each of the USA3,8, Spain4,5 and Portugal6,7 and one was in each of Argentina1 and Australia2.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (4 STUDIES)
- Abundance (3 studies): Two studies (one controlled), in Spain4 and Portugal7, found that artificial warrens increased European rabbit abundance. A replicated, randomized, controlled, before-and-after study in Argentina1 found that artificial refuges did not increase abundances of small vesper mice or Azara’s grass mice.
- Survival (1 study): A study in USA3 found that artificial escape dens increased swift fox survival rates.
BEHAVIOUR (4 STUDIES)
- Use (4 studies): Four studies (two replicated), in Australia2, Spain5, Portugal6 and the USA8, found that artificial refuges, warrens or nest structures were used by fat-tailed dunnarts2, European rabbits5,6, and Key Largo woodrats and Key Largo cotton mice8.
Background
Natural dens can reduce the vulnerability of animals to attack. Providing artificial dens and refuges may mimic natural dens, thereby reducing mortality as a result of predation. Refuges and dens may also provide protection from extreme weather conditions.
This intervention specifically covers situations where refuges or breeding sites are provided for existing wild mammal populations. For provision of refuges for translocated mammals, see Species Management — Release translocated/captive-bred mammals into area with artificial refuges/breeding sites. See also Provide artificial dens or nest boxes on trees for the specific intervention of providing boxes attached to trees.
A replicated, randomized, controlled, before-and-after study in 1995 in a sunflower field in Buenos Aires Province, Argentina (1) found that providing artificial refuges did not increase abundances of small vesper mice Calomys laucha or Azara’s grass mice Akodon azarae. The number of small vesper mice one to two months after refuges were placed did not differ significantly between plots with (4) and without refuges (5–8), and had not differed before refuges were placed (refuge plots: 14; no refuges: 18). Similarly, the number of Azara’s grass mice did not differ between plots with (9–30) and without refuges (5–20) one to two months after refuges were placed, and had not differed before they were placed (refuge plots: 37; no refuges: 34). In July 1995, 60 artificial shelters (12 cm long, 10 cm diameter tins with one entrance hole, provided with cottonwool and wrapped in paper and nylon bags) were half-buried at each of three randomly selected plots. Three other plots received no shelters. Mice were live-trapped for three consecutive nights in all six plots, one week before shelters were provided (late-July) and twice after (mid-August and early-September) using Sherman traps baited with peanut butter, laid 10 m apart in grids of 15 × 4 traps.
A study in 2000–2001 in a grassland and woodland reserve in Victoria, Australia (2) found that artificial log refuges were used by fat-tailed dunnarts Sminthopsis crassicaudata. Fat-tailed dunnarts were found beneath both recently placed (20 of 408 refuges) and old refuges (9 of 271 refuges) in grassland. However, introduced house mice Mus musculus were more often found beneath recently placed (10 of 408 refuges) than old refuges (1 of 271 refuges) in grassland. Fat-tailed dunnarts preferred Eucalyptus (34 of 447 refuges) to cypress-pine (9 of 684 refuges) posts, and preferred wider, more decayed posts with more holes (see paper for details). In May 2000, between 12 and 20 old white cypress-pine Callitris glaucophylla and Eucalyptus Eucalyptus sp. fence posts were placed in each of 91 quadrats (total 1,131 new refuges) throughout a 3,780-ha national park in grassland and woodland. Mammals were surveyed monthly, beneath both new refuges and beneath 271 old fence posts which had lain in the same grassland sites for more than 15 years. Surveys were conducted from June 2000 to January 2001 and between 08:00 h and 20:00 h.
A study in 2002–2004 in a grassland site in Texas, USA (3) found that artificial escape dens increased swift fox Vulpes velox survival rates. Average annual survival in plots with artificial escape dens (81%) was higher than in areas without such dens (52%). Six of 11 confirmed mortalities were due to predation by coyotes Canis latrans, three were of unknown causes, one died of natural causes and one was predated by a raptor. All mortalities were outside artificial den plots. Thirty-six artificial escape dens were installed 322 m apart in each of three 2.6-km2 plots within a 100-km2 study area. Two plots had established swift fox populations while the third did not. Each den was a covered, 4-m long, 20-cm diameter corrugated-plastic pipe with open ends. Fifty-five foxes were radio-collared and tracked, 2–4 times/week, for up to two years, between January 2002 and August 2004. Survival was estimated from 41 adult foxes (28 in artificial burrow plots, 13 in the study area but outside artificial burrow plots).
A controlled study in 2005–2007 in an open forest and scrubland site in Córdoba province, Spain (4) found that a plot with artificial warrens, water provision and fencing to excluding ungulate herbivores had more European rabbits Oryctolagus cuniculus than did a plot without these interventions. The three interventions were all carried out in the same plot, so their relative effects could not be determined. Average rabbit pellet counts were higher in the plot where the interventions were deployed (first year: 0.33 pellets/m2/day; second year: 1.08 pellets/m2/day) than in the plot without these interventions (first year: 0.02 pellets/m2/day; second year: 0.03 pellets/m2/day). A 2-ha plot was fenced to exclude ungulates in March 2005. Rabbits and predators could pass through the fence. Five artificial warrens were installed and water was provided at one place. No interventions were deployed in a second, otherwise similar, plot. Rabbit density was determined by monthly counts of pellets, from March 2005 to March 2007, in 0.5-m2 circles, every 100 m, along a 1-km transect in each plot.
A replicated, site comparison study in 2007 of pasture and scrubland on 14 estates in central Spain (5) found higher usage of artificial warrens where rabbit Oryctolagus cuniculus abundance was highest and that occupancy of tube warrens was higher than of stone warrens or pallet warrens. In grid squares where artificial warrens were used by rabbits, more rabbit latrines were found (13.5 latrines/km) than in squares where artificial warrens were not used (3.2 latrines/km). Authors report that it is unclear if artificial warrens boosted populations or if warren usage reflected pre-existing population levels. Occupancy of tube warrens (67% occupied) was greater than of stone or pallet warrens (54% occupied). Tube warrens (120 installed) comprised a labyrinth of concrete tubes 1 m underground. Stone warrens (207) were c.5 m diameter, with stones arranged to leave galleries and holes. Pallet warrens (198) were at least four wooden pallets, covered with soil. Rabbit latrines were surveyed along fixed routes within 98 squares in a 500 × 500 m grid, spread across 14 estates, in February–March 2007.
A replicated study in 2007–2009 in six agroforestry sites in Alentejo and Algarve, Portugal (6) found that European rabbits Oryctolagus cuniculus used most available artificial shelters. European rabbits used 65 out of 100 artificial shelters. Rabbit numbers were higher in areas where a higher percentage of artificial shelters were used (data presented as correlation). Between 2007 and 2009, a total of 100 artificial shelters were constructed across six agroforestry estates dominated by cork oak Quercus suber. Artificial shelters were clustered in groups of 6–8. Each shelter had six entrance points but no more details about shelters were provided. Shelters were surveyed once every three months during the first year after construction and once every six months thereafter. Shelters were considered in use if pellets were detected near their entrances. Rabbit relative abundance was assessed by the density of pellets within a 300-m radius around the shelter.
A study in 2007–2009 of a mixed woodland, scrub and agricultural area in southern Portugal (7) found that installing artificial warrens, along with other habitat management, increased presence and abundance of European rabbits Oryctolagus cuniculus. Rabbit presence and abundance were each higher within 100 m of artificial warrens than at greater distances (data reported as statistical model results). Rabbit numbers increased steadily through the study and artificial warrens achieved a 64% occupancy rate by 2009. A range of habitat management actions for rabbits was carried out from 2006 to 2009. These comprised managing scrubland, creating pastures and building 28 artificial warrens (constructed from wood pallets and vegetation remains, covered with soil). Rabbit presence and relative abundance were determined through latrine counts in 45 plots, located around two areas of rabbit activity. Counts were carried out in most months from July 2007 to June 2009.
A study in 2004–2013 in a forest reserve in Florida, USA (8) found that Key Largo woodrats Neotoma floridana smalli and Key Largo cotton mice Peromyscus gossypinus allapaticola used artificial nest structures. Out of 284 artificial nests, Key Largo woodrats were detected at 65 (23%) and Key Largo cotton mice at 175 (62%). Between 2004 and 2013, over 760 artificial nest structures for woodrats and cotton mice were built in the Crocodile Lake National Wildlife Refuge. Artificial nest structures ranged from boulders and rubble piles to recycled jet-ski structures, cinder blocks with PVC pipes, tin, and natural materials, and 1–2 m segments of plastic culvert pipes cut in half longitudinally and covered in natural materials. In April–May 2013, two hundred and eighty-four artificial nests were monitored using camera traps. One camera trap was set 0.5–3.0 m away from each nest. Cameras recorded for 5–6 nights/nest.
(1) Hodara K., Busch M. & Kravetz F.O. (2000) Effects of shelter addition on Akodon azarae and Calomys laucha (Rodentia, Muridae) in agroecosystems of central Argentina during winter. Mammalia, 64, 295–306, https://doi.org/10.1515/mamm.2000.64.3.295
(2) Michael D.R., Lunt I.D. & Robinson W.A. (2004) Enhancing fauna habitat in grazed native grasslands and woodlands: use of artificially placed log refuges by fauna. Wildlife Research, 31, 65–71, https://doi.org/10.1071/wr02106
(3) McGee B.K., Ballard W.B., Nicholson K.L., Cypher B.L., Lemons P.R. & Kamler J.F. (2006) Effects of artificial escape dens on swift fox populations in Northwest Texas. Wildlife Society Bulletin, 34, 821–827, https://doi.org/10.2193/0091-7648(2006)34[821:eoaedo]2.0.co;2
(4) Catalán I., Rodríguez-Hidalgo P. & Tortosa F.S. (2008) Is habitat management an effective tool for wild rabbit (Oryctolagus cuniculus) population reinforcement? European Journal of Wildlife Research, 54, 449–453, https://doi.org/10.1007/s10344-007-0169-0
(5) Fernández-Olalla M., Martínez-Jauregui M., Guil F. & San Miguel-Ayanz A. (2010) Provision of artificial warrens as a means to enhance native wild rabbit populations: what type of warren and where should they be sited? European Journal of Wildlife Research, 56, 829–837, https://doi.org/10.1007/s10344-010-0377-x
(6) Loureiro F., Martins A.R., Santos E., Lecoq M., Emauz A., Pedroso N.M. & Hotham P. (2011) O papel do programa lince (lpn/ffi) na recuperação do habitat e presas do lince-ibérico no sul de portugal. Galemys, 23:17–25.
(7) Godinho S., Mestre F., Ferreira J.P., Machado R. & Santos P. (2013) Effectiveness of habitat management in the recovery of low-density populations of wild rabbit. European Journal of Wildlife Research, 59, 847–858, https://doi.org/10.1007/s10344-013-0738-3
(8) Cove M.V., Simons T.R., Gardner B., Maurer A.S. & O’Connell A.F. (2017) Evaluating nest supplementation as a recovery strategy for the endangered rodents of the Florida Keys. Restoration Ecology, 25, 253–260, https://doi.org/10.1111/rec.12418
13.16. Provide artificial dens or nest boxes on trees
https://www.conservationevidence.com/actions/2584
- Thirty studies evaluated the effects on mammals of providing artificial dens or nest boxes on trees. Fourteen studies were in Australia8,9,12,13,15,16,18,19,21,22,24,27,29,30, nine were in the USA1–7,14,25, three were in the UK10,11,28, one was in each of Canada17, Lithuania20, South Africa23 and Japan26.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (6 STUDIES)
- Abundance (5 studies): Three of five controlled studies (three also replicated) in the USA2,14, the UK10, Canada17 and Lithuania20, found that provision of artificial dens or nest boxes increased abundances of gray squirrels2 and common dormice10,20. The other two studies found that northern flying squirrel14,17 and Douglas squirrel17 abundances did not increase.
- Condition (1 study): A replicated, randomized, paired sites, controlled, before-and-after study in Canada17 found that nest boxes provision did not increase body masses of northern flying squirrel or Douglas squirrel.
BEHAVIOUR (27 STUDIES)
- Use (27 studies): Twenty-seven studies, in Australia8,9,12,13,15,16,18,19,21,22,24,27,29,30, the USA1,3–7,14,25, the UK11,28, Canada17, South Africa23 and Japan26 found that artificial dens or nest boxes were used by a range of mammal species for roosting and breeding.
Background
Some mammals use cavities in trees for denning, roosting or breeding. Woodland management for timber extraction may disproportionately remove trees that are sufficiently mature to have developed such cavities. Nest boxes, usually made of wood and attached to tree trunks, may provide an environment that mimics natural tree cavities and is adopted by such mammals. This intervention includes creation of artificial cavities within the tree, by excavating a quantity of wood and replacing a front plate with a constricted opening. This intervention specifically includes artificial dens or nest boxes in or on trees. For provision of structures in other situations, see Provide artificial refuges/breeding sites.
A study in 1940–1947 in a forest site in Michigan, USA (1) found that artificial dens were used by raccoons Procyon lotor. Over the four years that 15 dens were monitored, 2–13 of them showed signs of being occupied by racoons. Fifteen dens were made of wood and measured 36 × 36 × 31 cm, with entrances measuring 10 × 15 cm. Dens were attached to trees in July 1940, at 7.5–12 m high. They were inspected for signs of racoon use in August, October, and November 1940, May 1941, June 1946, and June 1947.
A replicated, controlled, before-and-after study in 1963–1965 of a forest in Maryland, USA (2) found that areas with artificial dens had more gray squirrels Sciurus carolinensis than did areas without dens. No statistical analyses were performed. There were more gray squirrels after dens were installed (1.0–1.8 squirrels/acre) than before installation (0.6–0.9 squirrels/acre). Numbers were stable through this period in plots where dens were not installed (0.8–0.9 squirrels/acre over two years in one plot and 1.0–1.2 squirrels/acre over three years in another). Squirrels were surveyed by live-trapping in five woodland plots (9.5–26 acres extent) in January–February. Three plots were sampled in 1963 and all five in 1964 and 1965. Artificial dens (one den/1.25 acres) were attached to trees in one plot after surveys in 1963 and in two plots after surveys in 1964. Dens comprised half a car tyre, folded and fastened into a kidney-shaped box, with an entrance at the top.
A study in 1974–1977 in a forest plantation site in Utah, USA (3) found that nest boxes were used by Abert’s squirrel Sciurus aberti and red squirrel Tamiasciurus hudsonicus. After three years all 12 nest boxes installed were used by Abert’s squirrels. Additionally, a red squirrel was detected in one next box, one year after installation. In May 1974, twelve nest boxes (30 × 30 × 40 cm) were placed in a forest area. Boxes were secured 7.6–14 m high, to ponderosa pine Pinus ponderosa, and were checked periodically for signs of use until October 1977.
A replicated study in 1973–1975 of two stands of young hardwood trees in Ohio and Illinois, USA (4) found that nest boxes were used by gray squirrels Sciurus carolinensis at one site and by flying squirrels Glaucomys volans at both sites. At a 21–23-year-old forest stand, gray squirrels did not make active use of any of 10 boxes but flying squirrels occupied 7–10 boxes over six inspections. At a 32–36-year-old forest stand, gray squirrels occupied 7–18 boxes across five inspections and flying squirrels occupied 2–6 boxes. Ten boxes were installed in autumn 1973 in the 21–23-year-old stand, which covered 1.9 ha. They were inspected six times from April 1974 to November 1975. Twenty boxes were installed in April 1973 in the 32–36-year-old stand, which covered 4 ha. They were inspected five times from August 1973 to March 1975.
A study in 1977–1979 in three riverine forest sites in Louisiana and Mississippi, USA (5) found that nest boxes were used by Virginia opossums Didelphis virginiana, southern flying squirrels Glaucomys volans, fox squirrels Sciurus niger, gray squirrels Sciurus carolinensis, golden mice Ochrotomys nuttalli and eastern woodrats Neotoma floridana. Virginia opossums, southern flying squirrels and fox squirrels were more frequently detected in nest boxes than in natural cavities (opossums: 1.2% vs 0.2 of inspections; flying squirrels: 2.1% vs 0.2; fox squirrels: 0.7% vs <0.1%). Gray squirrels were detected with more similar frequencies in nest boxes (1.6 % of inspections) and natural cavities (1.1%). These comparisons were not subjected to statistical tests. Golden mice and eastern woodrats used next boxes rarely (<0.05% of box inspections). Boxes were erected in hardwood and hardwood/pine forests and were of three sizes: large (60 x 30 x 30 cm, 13 cm diameter entrance), medium (45 x 20 x 20 cm, 7.5 cm diameter entrance) and small (30 x 15 x 15 cm, 5 x 7 rectangle entrance). Fifty boxes were installed at two sites and 90 at the other. All boxes had 5–10 cm of pine shavings in the bottom. Boxes and natural cavities were inspected every month from April 1977 to February 1979.
A study in 1977–1980 in a range of agricultural, woodland and suburban areas across two counties in Tennessee, USA (6) found that nest boxes were used by gray squirrels Sciurus carolinensis, southern flying squirrels Glaucomys volans and occasionally opossums Didelphis virginianus. Over three years, gray squirrels were detected in 4–34% of boxes in agricultural sites, 0–19% in woodland and 12–49% in suburban areas. Southern flying squirrels were detected in 0–6% of boxes in agricultural sites, 0–26% in woodland and 0–9% in suburban areas. Opossums were detected only in 2% of boxes in suburban sites during the winter of one year. In 1977, one hundred and fifty wooden nest boxes were erected. Fifty were installed across an unstated number of agricultural sites (at a density of 1 box/1.4 ha), fifty were installed across three woodland sites (1 box/2.0 ha) and fifty were installed across three suburban areas around one city (1 box/2.5 ha). Boxes were 48 cm high, had a 7.6-cm diameter entrance hole and were nailed 4.6–6.1 m high on trees. They were inspected during March-June (spring) and December-February (winter) from 1978 and 1980.
A study in 1979 in a forest in Maryland, USA (7) found that artificial den cavities were used by southern flying squirrels Glaucomys volans and white-footed mice Peromyscus leucopus. Within 12 months, 84% of artificial cavities had been used by rodents or birds (data provided for both groups combined). Southern flying squirrels nested in the 40 artificial cavities six times and white-footed mice once. In July–August 1979, forty artificial cavities were created in a forest dominated by chestnut oak Quercus prinus. Cavities were created in 37 oaks, two pitch pines Pinus rigida and one white ash Fraxinus americana. Trees averaged 28 cm diameter at breast height. Cavities were 1.5 m above ground, were 15 × 13 cm across and 15 cm deep. The slab of wood initially removed from the tree surface was reattached across the front of the cavity with a 3.8-cm-diameter entrance hole.
A replicated study in 1977–1980 in two forest sites in Victoria, Australia (8) found that nest boxes were used by brown antechinus Antechinus stuartii, bobucks Trichosurus caninus, feathertail gliders Acrobates pygmaeus, sugar gliders Petaurus breviceps and greater gliders Petauroides volans. Out of the total of 240 nest boxes across the two sites, brown antechinus used 13 (5%), bobucks used seven (3%), feathertail gliders used 20 (8%), sugar gliders used 16 (7%) and greater gliders used one (<1%). Preference for diameter of entrance hole and height of box was significant for brown antechinus (tended to use 5 cm hole; avoided 8 m height) and sugar glider (tended to use 5 cm hole; selected 8 m height), but no other mammal species. In July 1977, 120 nest boxes were installed in each of two 4-ha forest sites dominated by eucalyptus. Sites were located 6.5 km apart. Boxes were made of 13-mm wide wood, were 22 × 31 cm across and 45 cm high. Entrance hole sizes were 5, 8, 12 or 15-cm in diameter and boxes were attached at heights of 1.5, 4 or 8 m on tree trunks. Nest boxes were installed 20 m apart. Each contained a 50-mm layer of wood shavings. They were inspected fortnightly, for six months after installation and then approximately monthly until January 1980.
A replicated study in 1982–1984 in woodland at four sites in Western Australia, Australia (9) found that nest boxes were used by mardos Antechinus flavipes. Within a 16-year-old regenerating block, all 36 boxes were used at least once, with 2–34 boxes being used across the 18 inspections. Single visits also revealed use of 7/34 boxes in virgin forest and 5/34 in streamside trees, but 0/34 were used in a 50-year-old regenerating block. Thirty-six nest boxes (internal volumes of 0.003–0.017 m3) were erected in each of four areas in June 1982. The 16-year-old block was 47-ha of regenerating karri forest. This was clearfelled in 1966 and prescribed burned in 1967. Boxes were fixed 3–5.5 m up trees. Further sites were virgin forest, retained streamside trees within a four-year-old regenerating block and a 50-year-old regenerating block. Boxes at these sites were set at 4.5–6.5 m height. Boxes were checked in the 16-year-old block monthly, from September 1982 to August 1983, then six further times to May 1984. Boxes at other sites were checked once, in May 1983.
A controlled study in 1986 in a woodland in Somerset, UK (10) found that nest boxes increased dormouse Muscardinus avellanarius abundance after 2–3 months. In woodland plots with nest boxes, more dormice were caught (8–11 dormice/plot) than in plots without nest boxes (3–6 dormice/plot). Within a 4-ha woodland, nest boxes were installed in two plots (0.8 and 1.2 ha), and two similar plots did not have nest boxes installed. Boxes, had internal dimensions of 115 ×130 × 120 mm and a 35-mm entrance hole. They were installed in May 1986, with the hole facing the tree, at a density of c.30 boxes/ha. Relative dormouse abundance in each plot was determined from live-trapping over 10 nights, simultaneously in box and non-box plots, in both July and August 1986.
A study in 1994–1997 in a coniferous forest in Lancashire, UK (11) found that red squirrels Sciurus vulgaris used all and bred in some nest boxes. Red squirrels used all boxes within the first three months of placement and used 16–26% of boxes for breeding each year. There was no significant difference in the use of large (18 boxes) and small nest boxes (10 boxes) by breeding females, or in the size of litters in large (2.7 young) and small (2.9) boxes. All age groups and both sexes used boxes. The study site was dominated by Scots pine Pinus sylvestris and Corsican pine Pinus nigra and contained a high density of red squirrels (3.5–4/ha in the spring). Three groups of five small (27 × 30.5 × 48 cm) and five large (32 × 35.5 × 56 cm) timber nest boxes were attached to pine trees a height of 5–8 m in February 1994. Boxes were 50 m apart and filled with hay. In 1995, eight additional large boxes were added. Boxes were waterproofed and had a 7.5-cm-diameter entrance. Boxes were checked monthly from summer 1994 to summer 1997.
A study in 1994–1996 in a forest site Victoria, Australia (12) found that nest boxes were used by feathertail gliders Acrobates pygmaeus and agile antechinus Antechinus agilis. Out of 40 nest boxes, feathertail gliders used nine (23%) and agile antechinus used one or two (3–5%). In total, 57 individual feathertail gliders and two agile antechinus used boxes. In January 1994, forty nest boxes were installed in a 7-ha forest area dominated by eucalyptus. Boxes were 50 m apart, had a 15-mm-wide slit as the entrance and were attached to tree trunks at approximately 4.5 m above ground. Nest boxes were checked approximately every two months, between July 1995 and May 1997. Inspections took place during daylight hours and all animals encountered were captured, individually marked and returned to the box.
A study in 1990–1993 in a rainforest in New South Wales, Australia (13) found that nest boxes were used by eastern pygmy-possums Cercartetus nanus. Over the first 16 months, the average monthly capture rate of eastern pygmy-possums was 33.5/100 nest box checks. Twenty-one months after the study commenced, part of the area was cleared and the average monthly capture rate dropped to 7.8/100 nest box checks. Ninety-eight individual pygmy-possums were caught in boxes over the study. The study was conducted in a 4-ha early regrowth rainforest plot at 1,200 m altitude. Between 28 and 55 nest boxes (the quantity changing through the study) were attached to tree trunks, 1.5–2.0 m above ground and 10–20 m apart. Boxes were made from 18-mm-wide pine wood, and were 17 × 17 cm and 25 cm tall, with a 1.5-cm-wide opening across the front under the lid. In February 1992, 1.4 ha of the study area was cleared by bulldozing and burning. Boxes were checked at least monthly, between June 1990 and December 1992, and in April 1993.
A replicated, randomized, controlled study in 1992–1998 in a forest in Washington, USA (14) found that artificial breeding sites were used by northern flying squirrels Glaucomys sabrinus but did not increase their abundance. Average northern flying squirrel abundance in sites with artificial dens (0.51–0.80 squirrels/ha) was not significantly higher than in sites without artificial dens (0.42–0.48 squirrels/ha). During 11 inspections of the 256 dens, a total of 349 northern flying squirrels, 201 Douglas’ squirrels Tamiasciurus douglasii and 16 Townsend’s chipmunk Tamias townsendii were detected. By the end of the study 74–80% of next boxes and 34–50% of artificial cavities were used. In 1992, 16 nest boxes (20 × 22 cm across and 22 cm tall, with a 3.8 × 3.8-cm entrance) and 16 artificial cavities (10 ×15 cm across and 18–33 cm tall with a 3.8 × 3.8 cm or 4.5-cm-diameter entrance) were added to eight of 16 Douglas-fir Pseudotsuga menziesii stands. Forest stands were 13 ha and located in four areas (≤4 km apart). Each area had two stands with supplementary dens and two stands without supplementary dens (each ≥ 80 m apart). Supplementary dens were 6 m high and were inspected once in summer and once in winter, from summer 1993 to summer 1998. Flying squirrels were trapped during 49,152 trap nights in 1997–1998, with two Tomahawk live traps at each of 64 samplings stations, in each stand.
A replicated study in 1996–2000 in three forest plantations and one native forest in Queensland, Australia (15) found that nest boxes were used by feathertail gliders Acrobates pygmaeus, sugar gliders Petaurus breviceps, squirrel gliders Petaurus norfolcensis and yellow‐footed marsupial mice Antechinus flavipes at three of four sites. Between 0 and 40% of nest boxes were occupied at each check within each of the three plantations. No boxes were used in the native forest. Out of 96 boxes, feathertail gliders used 16 (17%), sugar gliders used 10 (10%), squirrel gliders used four (4%) and yellow‐footed marsupial mice used one (1%). The study was conducted in three 2–18-year-old eucalyptus plantations (1.2–1.5 ha) and one native forest dominated by >30 year-old eucalyptus (1.8 ha). At each site, 24 boxes were attached to trees, 3 m or 6 m above ground and 2–25 m apart. Nest boxes (40 cm long, 20 cm wide, ≤18.5 cm deep) were made from laminated plywood and had a 15–20 mm wide slot at the bottom. Boxes were checked 5–9 times between April 1996 and November 2000.
A replicated study in 1998–2002 of two Eucalyptus regnans-forests in Victoria, Australia (16) found that nest boxes were used by four arboreal marsupial species, with large high boxes used more than smaller or lower boxes. No statistical analyses were performed. Leadbeater’s possum Gymnobelideus leadbeateri, mountain brushtail possum Trichosurus cunninghami, common ringtail possum Pseudocheirus peregrinus and eastern pygmy possum Cercartetus nanus were recorded. There were 38 records of presence of these species in large high boxes, 16 in small high boxes, 10 in large low boxes and 18 in small low boxes. In each of two forests, 12 locations were selected. Each had four trees in a 20 × 20 m square. At each location, a large high, large low, small high and small low box was installed in October–November 1998, one on each tree. Large and small box volumes were 0.038 m3 and 0.019 m3 respectively. High and low boxes were set at 8 m and 3 m height respectively. Boxes were checked 10 times to January 2002. Mammal occupancy was determined by animal presence, or hairs left on sticky devices.
A replicated, randomized, paired sites, controlled, before-and-after study in 1996–1999 in three forest sites in British Columbia, Canada (17) found that nest boxes were used by northern flying squirrels Glaucomys sabrinus and Douglas squirrels Tamiasciurus douglasii but did not increase their abundance or body mass. Northern flying squirrels occupied 68–83% of boxes with Douglas squirrels occupying 0–29%. However, two years after boxes were erected, the abundance and body mass of northern flying squirrels did not differ significantly between plots with nest boxes (abundance: 9.8/ha; body mass: 134 g) and plots without nest boxes (abundance: 7.7/ha; body mass: 128 g). At the same time, the abundance and body mass of Douglas squirrels also did not differ significantly between plots with nest boxes (abundance: 15.1/ha; body mass: 198 g) and plots without nest boxes (abundance: 20.1/ha; body mass: 207 g). In February–March 1997, thirty nest boxes (12.8 × 13.6 × 15.5 cm), 100 m apart in a 5×6 grid and 5.5 m above ground, were mounted in each of three 30-ha plots. Three other 30-ha plots had no nest boxes. In each plot, squirrels were trapped every 5–6 weeks during the snow-free period, from June 1996 to March 1999, using 80 baited Tomahawk live traps, at 40-m intervals in an 8×10 grid.
A replicated study in 1993–1994 in 20 forest sites in Victoria, Australia (18) found that nest boxes were used by common brushtail possums Trichosurus vulpecula and common ringtail possums Pseudocheirus peregrinus. Over one year, common brushtail possums were detected in 43% (52) and common ringtail possums in 33% (40) of the available 120 nest boxes. The average occupancy rate of nest boxes per monthly survey was 9% for common brushtail possums and 10% for common ringtail possums. In July 2003, 120 nest boxes were installed in 20 randomly selected (from 44) forest fragments (<2 ha) within a 183-km2 study area. Boxes were of two designs (12 or 25-mm-wide plywood; 30 × 30 x 27.5 or 30 cm high), had a 10-cm diameter entrance hole and were attached to tree trunks approximately 4 m above the ground. Nest boxes were installed 50 m apart, on either side of a 100-m transect crossing the centre of each fragment. Nest box monitoring commenced eight weeks after installation and each box was inspected monthly over one year.
A replicated study in 2002–2003 in four forest sites in New South Wales, Australia (19) found that nest boxes were used by eastern pygmy-possums Cercartetus nanus and brown antechinus Antechinus stuartii. Five individual pygmy-possums (three of which were encountered twice) at one site and five brown antechinus were detected over 264 nest box inspections. Additionally, nesting materials characteristic of pygmy-possums was detected in eight nest boxes at the one site and brown antechinus in 11 nest boxes across the sites. The study was conducted in four 1-ha sites within a 2,000-ha forest reserve. In July-November 2002, forty nest boxes were attached to tree trunks, 1–2 m above the ground. Boxes had a 15-mm-wide entry slot and were placed 10–20 m apart. Boxes were checked eight times, with visits in alternate months in 2002 and then monthly.
A controlled, before-and-after study in 1985–1989 and 2000–2003 in a forest site in Lithuania (20) found that after more nest boxes were provided, common dormouse Muscardinus avellanarius density approximately doubled. Dormouse density was higher when there were 16 boxes/ha (0.9–3.0 dormice/ha) than when there were 4 boxes/ha (0.3–1.5 dormice/ha). Dormouse density did not increase in an area where next box provision remained at 4 boxes/ha (after: 0.6–0.9 individuals/ha; before: 0.7–1.3 individuals/ha). The study was conducted in 60 ha of a 40–50-year-old forest. In 1985–1999 wooden nest boxes (12 × 12 × 24 cm) were installed in a 50 × 50 m grid (276 boxes, 4 boxes/ha). In 2001, eighty-five additional nest boxes were added to a 6.25-ha section of the forest to form a 25 × 25 m grid (increasing box density to 16 boxes/ha). Boxes were inspected twice each month from April until October in 1985–1989 and 2000–2003.
A replicated study in 2005–2007 in five eucalyptus plantation sites in New South Wales and Queensland, Australia (21) found nest boxes were used by five marsupial species with different frequencies, depending on box type. Feathertail gliders Acrobates pygmaeus used 15 of 45 available small rear-entry boxes, 10 large slit-entrance boxes and nine wedge-shaped boxes, but did not use any medium rear-entry boxes. Squirrel gliders Petaurus norfolcensis used 18 of 45 medium rear-entry boxes and three large slit-entry boxes. Yellow-footed antechinus Antechinus flavipes used two large slit-entry boxes and one medium rear-entry boxes. Brown antechinus Antechinus stuartii used three small rear-entry boxes and brush-tailed phascogales Phascogale tapoatafa used one large slit-entry box. Nest boxes were of four types, small rear-entry boxes (height×width×depth: 23×14×14 cm, 25-mm-diameter entrance), large slit-entrance boxes (48×28×18.5 cm, 1.5×15 cm entrance on the side), wedge-shaped boxes (19×16×12.5–5 cm, 2×16 cm entrance at the base) and medium rear-entry boxes (40×14.5×14 cm, 45-mm-diameter entrance). They were installed in February–March 2005 and March 2006, 3 m above ground, in 45 plots. Each plot had one of each box type (180 boxes in total). Boxes were surveyed five times over 22 months.
A study in 1993–2005 of restored sites within bauxite mined areas in the jarrah Eucalyptus marginata forest of Western Australia, Australia (22) found that nest boxes within restoration areas were used by western pygmy possums Cercartetus concinnus, mardo Antechinus flavipes and brush-tailed phascogale Phascogale tapoatafa. Western pygmy possum used nest boxes placed in 8–10-year-old restoration sites. Mardo and brush-tailed phascogale also used nest boxes and possibly bred in them (no further details provided). Mined areas were revegetated using various techniques. In 1993–1994, mammal nest boxes were placed in a range of sites. Control of non-native red foxes Vulpes vulpes was also carried out for several years from 1994. Nest box designs and monitoring protocols are not described.
A study in 2003–2007 in a forest reserve in Eastern Cape, South Africa (23) found that nest boxes were used by woodland dormice Graphiurus murinus and Mozambique thicket rats Grammomys cometes. Out of 70 nest boxes, at least 49 (70%) were occupied by dormice and seven (10%) by thicket rats. Dormouse nest box occupation was lowest during winter (3% of boxes) and peaked in spring (8%) and summer (9% of boxes). Over one year, at least 66 dormice used between one and 16 next boxes (average 4). More adult females (17) than adult males (11) used nest boxes, but they were used by similar numbers of adults (30) and juveniles (36). Between March 2003 and January 2006, seventy wooden nest boxes (11.5 × 13 × 12 cm) were erected across a 2.5-ha area. Boxes had a 3-cm-diameter entrance hole facing the tree trunk. Boxes were installed 1.1–2.4 m above the ground, in trees with an average trunk diameter at nest box height of 90 cm. Boxes were monitored 57 times (average 4.4 times/month) between June 2006 and June 2007. Captured dormice were individually marked to determine recaptures.
A study in 2003–2006 of 16 woodland fragments in Queensland, Australia (24) found that 20% of nest boxes were used by squirrel gliders Petaurus norfolcensis. In total, 11 out of 56 nest boxes were occupied at least once by squirrel gliders, with presence detected 15 times out of 318 box visits. No squirrel gliders were found in boxes until ≥18 months after placement. Four of the boxes were occupied by five female gliders with young. In 16 woodland remnants (from <50 ha to >1,000 ha in extent), 56 nest boxes were erected in September–December 2003. Boxes were 40 cm high, 25 cm wide and 18 cm deep. They were installed ≥3 m above the ground. There were 2–6 boxes/site, with the number dependent on site size. Boxes were checked at six-month intervals from summer 2003 to summer 2006.
A study in 2008–2011 in a forest area in North Carolina, USA (25) found that nest boxes were used by northern flying squirrels Glaucomys sabrinus. Sixteen northern flying squirrels were caught at nest boxes. The study was conducted in a forest area dominated by eastern hemlock Tsuga canadensis. The number of nest boxes used was not detailed. Nest boxes measured 30 × 18 × 15 cm, had a 5 × 5-cm entrance, and were attached 3.6 m up the trunks of trees using nails and wire. They were monitored in winters of 2008 to 2011 and in spring 2009. Captured flying squirrels were individually tagged.
A study in 2004–2005 in a forest reserve in Nagano Prefecture, Japan (26) found nest boxes were used by Japanese dormouse Glirulus japonicus. Of 200 nest boxes, at least 127 (64%) were occupied by dormice. Thirty-nine individuals used the nest boxes (total 82 captures), 23 males and 16 females. The number of dormice captured in nest boxes peaked in August 2004 and June 2005 (14 captured/month) and October in both years (10–13). Pup-rearing was observed twice in nest boxes. The average diameter at breast height of trees with used nest boxes (33 cm) was smaller than unused boxes (51 cm). In early 2004, two hundred nest boxes were installed at equal distances across a 3.8-ha area of dense deciduous forest. Nest boxes were constructed from 12-mm-wide pinewood boards with a 35 x 35 mm square entrance at one side. Boxes were attached to trees with a diameter at breast height <40 cm, at a height of 1.0–1.2 m. Boxes were checked 2–4 times/month (total 76 times) between April 2004 and October 2005. Captured dormice were individually marked. Nest boxes were considered occupied when either dormice were present or when nesting materials were found.
A replicated study in 2003–2014 in one urban and two rural forest sites in New South Wales and Queensland, Australia (27) found that nest boxes were used by six species of arboreal marsupial. Within the rural landscapes nest boxes were occupied by sugar gliders Petaurus breviceps (29% of available boxes, use affected by design), brown antechinus Antechinus stuartii (23%, use unaffected by design), mountain brushtail possums Trichosurus caninus (1%) and feathertail gliders Acrobates pygmaeus (1%). Within an urban landscape, nest boxes were occupied by common brushtail possum Trichosurus sp. (20% of available boxes), common ringtail possum Pseudocheirus peregrinus (4%), and sugar gliders (4%). Use of some nest boxes influenced by design (see original paper for details). All boxes accessible to squirrel gliders Petaurus norfolcensis at two sites were used by them over a 10-year period (6–21 adults/year in boxes; total 61 individuals). Nest boxes of five different types (11–42 × 15–29 × 26–45 cm, 3.5–21-cm diameter entrance) were installed 3–6 m above ground. In the rural landscape, five boxes in each of 32 plots (25 x 25 m; ≥ 200 m apart) were installed across nine sites (>1 km apart). At the urban site a total of 188 boxes were installed across 20 sites. Boxes were erected in 2003–2007 and inspected three times in 2008–2009 at the rural sites and once in August 2010 at the urban site. In 2005–2009, 16 additional boxes were installed or adapted for squirrel gliders across two sites and were inspected usually once/year in 2005–2014.
A study in 2003–2016 in a coniferous forest plantation in Dumfries and Galloway, UK (28) found that pine martens Martes martes occupied and, in most years, bred in den boxes. Each year, 30–70% of available den boxes were occupied by pine martens. Martens used 5–20% of den boxes for breeding, in 10 of the 12 years monitored. The study was conducted in an 800-km2 forest into which 12 martens were reintroduced in 1980–1981. Fifty den boxes (55 cm high, 51 cm wide, 24 cm deep) were fitted to trees at approximately 4 m high. Ten boxes were installed in 2003 and 40 in 2013. Boxes were made of wood, had two entrances and had 10 cm depth of softwood shavings inside the chamber. Boxes were checked for martens, signs of use by martens and marten kits, once/year in 2004–2016 (excluding 2013).
A study in 2010–2013 of planted and remnant woodland patches at 30 sites in New South Wales, Australia (29) found that nest boxes were used by five native and one non-native mammal species. Use of boxes was detected for yellow-footed antechinus Antechinus flavipes (two detections), sugar glider Petaurus breviceps (two detections), common brushtail possum Trichosurus vulpecula (52 detections), common ringtail possum Pseudocheirus peregrinus (eight detections) and lesser long-eared bat Nyctophilus geoffroyi (four detections). The introduced black rat Rattus rattus was also detected on 24 occasions. One each of five nest box designs was placed at 30 sites. Sites comprised seven connected woodland plantations, nine isolated woodland plantations (>70 m from native vegetation), eight connected remnant woodlands, and six isolated remnant woodlands (>70m from native vegetation). Boxes were erected in February 2010 and checked in October 2010, December–January of 2010–2011, October 2011 and December–January of 2012–2013. Mammals were identified from live animals or from signs, such as faeces.
A study in 2010–2013 in a eucalypt forest in New South Wales, Australia (30) found that nest boxes were used by a range of native and non-native mammal species. Yellow-footed antechinus Antechinus flavipes were found in 12–14% of nest boxes, common brushtail possum Trichosurus vulpecula in 11–13%, and common ringtail possum Pseudocheirus peregrinus in 3–7%. Brush tailed phascogale Phascogale tapoatafa, squirrel glider Petaurus norfolcensis, and sugar glider Petaurus breviceps were all found in <1% of nest boxes. The non-native black rat Rattus rattus was found in 4–14% of boxes and the house mouse Mus musculus in 0–2% of boxes. On an unspecified date, 587 nest boxes were installed in a woodland. Animal presence, or signs of presence, were recorded during six surveys in 2010–2013.
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13.17. Provide more small artificial breeding sites rather than fewer large sites
https://www.conservationevidence.com/actions/2595
- One study evaluated the effects on mammals of providing more small artificial breeding sites rather than fewer larger sites. This study was in Spain1.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): A replicated, controlled study in Spain1 found that smaller artificial warrens supported higher rabbit densities than did larger artificial warrens.
BEHAVIOUR (0 STUDIES)
Background
When providing artificial breeding sites for colonial mammals, there may be a trade-off between providing large sites, which may support larger, more-resilient populations at each site, or a greater number of small sites, which may increase the chance of at least some sites surviving threats such as predation or disease. The size of the overall population may also be influenced if the density of animals occupying these sites differs between different sized sites.
A replicated, controlled study in 2002–2005 of two grassland and scrubland plots at a site in Andalucia, Spain (1) found that providing smaller artificial warrens for wild rabbits Oryctolagus cuniculus supported higher rabbit densities than did larger artificial warrens. Rabbit density was higher in small artificial warrens (4–13 rabbits/12 m2 plot) than it was in large artificial warrens (11–24 rabbits/48 m2 plot). Two plots (4 ha each, 2 km apart) were fenced to exclude terrestrial predators. Each plot had 18 artificial warrens, comprising 12 small and six large warrens. Warrens were skeletons of wooden pallets covered by earth and branches. Large warrens (48 m2) were the size of four small warrens (12 m2). In autumn 2002, five rabbits were released into each small warren, and 20 rabbits were released into each large warren. Rabbits were surveyed by live-trapping, three times, from November 2004 to May 2005.
(1) Rouco C., Villafuerte R., Castro F. & Ferreras P. (2011) Effect of artificial warren size on a restocked European wild rabbit population. Animal Conservation, 14, 117–123, https://doi.org/10.1111/j.1469-1795.2010.00401.x