Caribou calf mortality in Denali National Park, Alaska

Journal of Wildlife Management

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Calf mortality is major component of caribou 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 (less than or equal to 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 (less than or equal to 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 greater than 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 less than 0.001) neonatal survival than did other calves. Grizzly bears, wolves, 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 less than 0.001) with calf age, and bears killed few calves greater than 10 days old. Wolf predation was not related (P greater than 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 DCH.

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Journal Article
Caribou calf mortality in Denali National Park, Alaska
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Journal of Wildlife Management
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Alaska Biological Science Center
pp. 584-594
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Journal Article
Larger Work Title:
Journal of Wildlife Management
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