Experimental analyses of dispersal in snowshoe hare populations

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Abstract
Dispersal was investigated in snowshoe hare (Lepus americanus) populations near Rochester, Alberta, from May 1970 to May 1974. Ingressing hares (dispersers) were removed every 3 to 4 weeks after removal of the initial resident population from an 11.3-ha study area. Dispersal into this vacant habitat occurred during all seasons of each year. The highest rates of ingress were recorded during the winter of peak population densities (1970–1971). There was a higher proportion of short-yearlings among ingressing hares than among residents. During two winters of known food shortage (1970–1971 and 1971–1972) dispersing hares had lower body weights than residents. Lighter adrenals and a higher incidence of scarring were also found among ingressing hares during winter 1970–1971.During winter 1971–1972 the resident hare population was removed from another area. Comparable recapture rates between marked immigrants on this area and hares on unmanipulated study areas indicated that ingressing individuals had settled in the vacant habitat.Hare population response to sex-ratio imbalance, created by partial removal of each sex on different areas, was studied during 1970 and 1971. Pregnancy rates declined significantly only on the male-removal area. Movements by adults during the breeding season and by predominantly juveniles over winter tended toward rebalancing population sex ratios.