During January‐April 1989. we monitored survival, reproduction, and body condition of 19 radio‐collared arctic haresLepus areticusintroduced to two predominantly (80%) forested islands. Merchant (66 1 ha) and Burke (82 6 ha), in Placentia Bay, Newfoundland By late April, bone‐marrow fat (42 7%) and kidney fat indices were lower than found in populations on the mountain barrens of western Newfoundland However, most island hares gained weight overwinter, and litter sizes (mean. 4 2 in utero) and testis weights (mean, 8 3 g) were as large or larger than recorded from other introduced and natural populations in Newfoundland The distribution of telemetry locations, tracks and feeding sites indicated that hares frequented the scattered barrens (totalling c 30 ha) on both islands in greater proportion than available These results suggest that, in the absence of snowshoe hares and mammalian predators, forested regions interspersed with small patches of barrens can sustain arctic hares

We describe dispersion of radio-collared arctic hares (Lepus arcticus) introduced to three islands off Newfoundland's south coast. Nearest-neighbor analyses indicated that home-range activity centers were aggregated during both summer and winter. Mean distances between activity centers were significantly less during winter than during summer, with the greatest aggregation observed when rates of fox predation were least and snow depth and persistence were greatest. Arctic hares apparently lack a rigid social-dominance system; hence, environmental factors such as availability of food sources, snow conditions, and presence of predators may primarily influence dispersion.

Geographic distributions of arctic (Lepus arcticus) and snowshoe hares (Lepus americanus) do not overlap on insular Newfoundland, where snowshoes were introduced, or in continental North America, where both species are indigenous. We conducted a field experiment to explore the role of interspecific competition in maintaining this allopatry. In September of 1984 and 1985, single- and mixed-species populations of arctic and snowshoe hares were established as "treatments" on six islands off Newfoundland's southwest coast. Island treatments differed between years. Demographic elements of each species population were monitored as potential response variables. Neither snowshoe nor arctic hares were demographically affected by the sympatry imposed in this experiment. Survival, reproduction, recruitment, habitat use, home range size, and over-winter weight change did not differ between single- and mixed-species treatments. There were, however, major demographic responses when each species was forced to occupy only atypical habitat, i.e., habitat normally used by the other species. Thus, most arctic hares confined to forested islands died from starvation in 1–3 months, after weight losses of 20–30% and marrow-fat reductions to <15%. Such responses occurred during winter and early spring, regardless of whether snow-shoe hares were present. In contrast, arctic hares at similar densities in their typical barrens habitat maintained weight and survived well. Snowshoe hares also maintained weight when restricted to barrens, but unlike those in forest habitat, were rapidly decimated by raptor predation. We believe that lack of suitable food over winter, rather than interspecific competition, has been a major constraint on the arctic hare's ability to populate forested regions of Newfoundland, whereas heavy predation has prevented snowshoe hares from colonizing mountain and coastal barrens.