Habitat selection and demography of a nonmigratory woodland caribou population in Newfoundland

Several studies have shown that habitat selection and population limitation of woodland caribou (Rangifer tarandus caribou) is typically associated with the interaction among human-induced habitat alteration, wolf predation (Canis lupus), and the availability of alternative prey such as moose (Alces alces) and white-tailed deer (Odocoileus virginianus). Although woodland caribou inhabiting Newfoundland have been exposed to moderate levels of timber harvesting, black bears (Ursus americanus), not wolves, are the principal large predator in this system, and moose represent the alternative large prey species. During a 4-year period of timber harvesting, the authors monitored the location and status of 24 adults and 46 calves to determine coarse-scale habitat selection and survival rates of a nonmigratory and demographically isolated woodland caribou herd in Newfoundland. The authors also estimated pregnancy and recruitment rates and determined potential causes of mortality. Habitat selection significantly varied among seasons but was consistent with the hypothesis that caribou avoid habitats where the likelihood of contact with a predator or alternative prey was high. Population growth rate (rs = –0.01 ± 0.06 (mean ± 1SD)), calf recruitment (percentage of 10-month old calves = 13%), and adult survival rate (0.87) indicated that the population was stable. Mean pregnancy rate (96%), parturition date, and the lack of evidence for malnutrition in 22 carcasses suggested that the availability of quality forage is not a key factor limiting population growth. Although predation could not be linked to the death of adult caribou, black bears were responsible for 5 of 15 calf fatalities. This study suggests that black bears need to be considered more seriously as a factor influencing coarse-scale habitat selection and demography in woodland caribou herds.