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Caribou Calf Mortality in Denali National Park, Alaska
Layne G. Adams, Francis J. Singer and Bruce W. Dale
The Journal of Wildlife Management
Vol. 59, No. 3 (Jul., 1995), pp. 584-594
Stable URL: http://www.jstor.org/stable/3802467
Page Count: 11
You can always find the topics here!Topics: Calves, Caribous, Wolves, Calving, Mortality, Bears, Predation, Predators, Neonates, National parks
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Calf mortality is a major component of caribou (Rangifer tarandus) population dynamics, but little is known about the timing or causes of calf losses, or of characteristics that predispose calves to mortality. During 1984-87, we radiocollared 226 calves (≤3 days old) in the Denali Caribou Herd (DCH), an unhunted population utilized by a natural complement of predators, to determine the extent, timing, and causes of calf mortality and to evaluate influences of year, sex, birthdate, and birth mass on those losses. Overall, 39% of radio-collared calves died as neonates (≤15 days old), and 98% of those deaths were attributed to predation. Most neonatal deaths (85%) occurred within 8 days of birth. Few deaths occurred after the neonatal period (5, 10, and 0% of calves instrumented died during 16-30, 31-150, and >150 days of age, respectively). Survival of neonates was lower (P = 0.038) in 1985, following a severe winter, than during the other 3 years. In years other than 1985, calves born during the peak of calving (approx 50% of the total, born 5-8 days after calving onset) experienced higher (P < 0.001) neonatal survival than did other calves. Grizzly bears (Ursus arctos), wolves (Canis lupus), and unknown large predators (i.e., grizzly bears or wolves) accounted for 49, 29, and 16% of the neonatal deaths, respectively. The rate of bear-caused mortalities declined (P < 0.001) with calf age, and bears killed few calves >10 days old. Wolf predation was not related (P > 0.05) to calf age and peaked 10 days after onset of calving. Grizzly bear and wolf predation on neonates during the calving season was a limiting factor for the Denali Caribou Herd.
The Journal of Wildlife Management © 1995 Wiley