A key strategy for animals successfully reinvading areas is to have high rates of dispersal. One method for measuring rates of dispersal of small mammals into
vacant areas is to experimentally remove animals from grids. SCHIECK & MILLAR (1987) studied the response of red-backed voles (Clethrionomys gapperi) to removal
trapping in a mountain fir forest in Alberta Canada and found that about 80% of the voles caught in the removal area originated from a distance of less than two home
ranges away. NAKATA & SATOH (1994) studied the response of individual grey-backed voles (Clethrionomys rufocanus bedfordiae) to removal trapping to determine the source of animals moving into the removal grid and the distance that these animals moved from source areas. After 2 weeks, over 90% of the voles initially located within 30 m of the edge of the removal grid were making single-direction movements towards the removal grid. Conversely, BOUTIN et al. (1985) found that only 28% of snowshoe hares (Lepus americanus) dispersed into removal areas and that most animals died on their home range rather than dispersing, while SULLIVAN & SULLIVAN (1986) found that the colonization rate was 25 – 58% per
four-week period