Action: Restore or create shrubland
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- Three studies evaluated the effects on mammals of restoring or creating shrubland. Two studies were in the USA and one was in Mexico.
COMMUNITY RESPONSE (2 STUDIES)
- Richness/diversity (2 studies): Two site comparison studies, in the USA and Mexico, found that following desert scrub or shrubland restoration, mammal species richness was similar to that in undisturbed areas.
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): A site comparison study in the USA 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 USA found that restoring shrubland following tree clearance did not increase usage of areas by mule deer compared to tree clearance alone.
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.
Supporting evidence from individual studies
A site comparison study in 1995 in a desert site in California, USA (Patten 1997) 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 (San-José et al. 2013) 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 (Bergman et al. 2015) 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.
- Patten M.A. (1997) Reestablishment of a rodent community in restored desert scrub. Restoration Ecology, 5, 156-161
- 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
- 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