Population dynamics of northern white-tailed deer during mild winters: evidence of regulation by food competition

We studied white-tailed deer (Odocoileus virginianus borealis) at the north eastern limit of their range after their density had decreased as a result of harsh winters aggravated by coyote predation. We compared two population s wintering in adjacent areas. In the Lac Temiscouata wintering area (LTWA) , deer and browse density averaged 10 animals/km(2) and 127 000 deciduous t wigs/ha compared with 20 deer/km(2) and 68 000 twigs/ha, respectively, at t he Pohenegamook wintering area (PWA). For 75 radio-collared deer, the proba bility of death was highest during the short spring migration and remained elevated in winter, whereas fewer deaths occurred in summer and none during autumn migration. PWA deer had a higher mortality rate than did LTWA anima ls and died mostly in winter, from predation, starvation, and collision equ ally. Based on observed survival rates, we estimated that the finite rate o f increase averaged approximately 1.25 and approximately 1.00 for LTWA and PWA populations, respectively. At PWA, we examined 129 carcasses to determi ne the mortality pattern of deer. Among adults, we did not detect significa nt differences related to sex. Starvation and predation affected more fawns and old deer than prime animals, whereas collision appeared to be nonselec tive. Most cases of starvation occurred after the beginning of March, when body reserves dropped to low levels. We conclude that competition for winte r forage regulated PWA deer during the study.