Individual study: Optimal width of movement corridors for root voles Microtus oeconomus, Evenstad Field Station, Hedmark, Norway
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
Negative effects of habitat fragmentation may perhaps be reduced by connecting isolated habitat fragments by narrow strips of habitat known as wildlife or movement corridors. In this Norwegian study, movement behaviour of the root vole Microtus oeconomus, in experimental corridors of varying width was investigated.
Study site: At Evenstad Field Station in southeast Norway, the characteristics of male root vole movements as a function of corridor width were tested in a 310 m long habitat corridor of meadow vegetation connecting two patches of meadow.
Observations: During August-October 1992 within the purpose built corridor, observations of root vole movements were made by means of radio-telemetry and recording of footprints. Three different corridor widths were tested, starting with the widest corridor of 3m. The two narrower corridors (1 m and 0.4 m) were subsequently made by mowing the corridor edges and herbicide use.
Competitor and predator simulation: Competitor and predator presence was simulated by six ‘barrier cages placed across the corridor at fixed distances. These were made of wire mesh and contained one live adult male vole to mimic presence of competitors, or fresh fox Vulpes vulpes scats to simulate the presence of a predator.
In terms of movement rate of individual voles in the corridor system, the highest connectivity was observed in the intermediate of three corridor widths tested i.e. 1 m in width.
The behavioural mechanism behind the lower connectivity of the narrowest corridor was a reluctance of voles to enter it, while linear progress in the widest corridor was slower due to a high frequency of cross-directional movements.
The relationship between corridor width and movement behaviour was unaffected by the simulated presence of competitors and predators.
Conclusions: The results of this study challenge the 'the-wider-the-better' principle of movement corridor design, and give an insight into the behavioural mechanisms underlying the movement behaviour of small mammals in linear habitats.
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