Action: Create or maintain corridors between habitat patches
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- Four studies evaluated the effects on mammals of creating or maintaining corridors between habitat patches. One study was in each of Canada, the USA, Norway and the Czech Republic.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (0 STUDIES)
BEHAVIOUR (4 STUDIES)
- Use (4 studies): Four studies (three replicated) in Canada, the USA, Norway and the Czech Republic found that corridors between habitat patches were used by small mammals. Additionally, North American deermice moved further through corridors with increased corridor width and connectivity and root voles moved further in corridors of intermediate width.
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.
Supporting evidence from individual studies
A replicated, site comparison study in 1989 of woodland blocks and connecting woodland and grassland corridors at a site in Ontario, Canada (Bennett et al. 1994) 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 (Ruefenacht & Knight 1995) 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 (Andreassen et al. 1996) 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 (Bryja & Zukal 2000) 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.
- 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
- Ruefenacht B. & Knight R.L. (1995) Influences of corridor continuity and width on survival and movement of deermice Peromyscus maniculatus. Biological Conservation, 71, 269-274
- 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
- Bryja J. & Zukal J. (2000) Small mammal communities in newly planted biocorridors and their surroundings in southern Moravia (Czech Republic). Folia Zoologica, 49, 191-197