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Abstract

In this study I compared a non-cyclic island population of snowshoe hares (Lepus americanus) with a cyclic mainland population to determine how the dynamics of the two populations differed following a population decline. Both populations had declined to similar low levels by the fall of 1992. During this study the Jacquot Island hare population increased 3.5 fold from the spring of 1993 to the spring of 1994 while the cyclic mainland hare population remained at low densities. I monitored survival and reproduction to determine the proximate causes for the different dynamics seen. I determined that juvenile survival, overwinter adult survival and reproduction were higher on Jacquot Island than the mainland from the spring of 1993 to the spring of 1994. These were the key proximate factors that allowed the Jacquot Island hare population to increase while the mainland population remained at low densities. There was no difference in summer adult survival between the two areas in 1993. I also investigated the ultimate causes for the different dynamics seen in the two areas. Higher reproductive output, and higher overwinter survival did not coincide with better hare condition on Jacquot Island. There were, however, fewer mammalian predators on Jacquot Island than the mainland. Higher early juvenile survival on Jacquot Island coincided with lower numbers of small mammal predators.