Demography and ecology of the arctic hare (Lepus arcticus) in southwestern Newfoundland

Abstract

We determined demographic attributes of an arctic hare (Lepus arcticus) population in the Southern Long Range Mountains of Newfoundland. Twenty-four adult hares were livetrapped, radio collared, and monitored from July 1981 through July 1984. From livetrapping and an aerial census we estimated mean density at about 1 adult/km2. A single litter was born annually and natality averaged 3.0 young/female. Mean dates of conception and parturition were 19 April and 8 June, respectively. Annual survival rate of radio-collared adults was 0.78; calculated 1st-year survival rate of juveniles was 0.15. Natural mortality was mainly from red foxes (Vulpes vulpes). One-year-old individuals comprised 18% of 68 adult hares shot in May. Sex ratios were biased towards males in both trapped and shot samples. Summer home range size of three adult females (52–69 ha) averaged half that of three adult males (116–155 ha). Movements increased in March and April with onset of breeding activity. It is unlikely that winter food shortage affected survival, as hares collected in May had both kidney fat and relatively high levels of bone marrow fat. Annual differences in these condition indices were, however, reflected in several reproductive parameters. We hypothesize that the single litter and small litter size which combine to give Newfoundland arctic hares the lowest reproductive potential of any known hare population are a consequence of (i) the late spring that delays onset of breeding until April, and (ii) the shorter day length in April and hence lower gonadotrophin levels at this southernmost limit of distribution. We believe that predation on juveniles is the paramount limitation on growth of this arctic hare population, and primarily responsible for the stabilization at low densities.