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.

Demographic responses of arctic hares (Lepus timidus) to experimental reductions of red foxes (Vulpes vulpes) and martens (Martes martes)

“…We tentatively concluded earlier than natality on Rinon and on Bergon during 1987 averaged about seven young per female, comparable to the annual mean of 6.9 (range 6.1 -8.7) in nine other arctic hare populations (summarized in Hearn et al 1987). The single exception to this natality rate occurred in Newfoundland with just three young per female.…”

“…(Survival may have been much higher in a 4th increase year, 1980, however.) First-year survival was reportedly 18% in the stationary Newfoundland population (Hearn et al 1987), and we estimate it averaged about 20% overall in the fluctuating population studied by …”

“…First-litter conception dates were obtained by aging embryos or preimplantation corpora lutea and backdating accordingly (Hearn et al 1987).…”

An experimental study of red fox predation on arctic and snowshoe hares

“…Sex, age, and weight of each hare were recorded prior to radio-marking and subsequent release for a predation trial. During June-February we identified adults and juveniles through reproductive status and genital traits (Keith et al 1968;Hearn et al 1987).…”

Demographic data on the woolly hare Lepus oiostolus near Lhasa, Tibet

“…Ecological harshness in the highaltitude environments, including inclement climates, limited food supply as well as poor oxygen availability in association with metabolic efficiency, could constrain the ability of these animals to invest more in offspring production in terms of both the number of litters and the number of fetuses in each litter. In contrast, for highlatitude L. arcticus, where a single litter that generally contains 3 young was born annually, the limited reproductive potential was attributed to the shorter day length during the breeding season and hence lower gonadotrophin levels (Hearn et al 1987).…”