BEAR PREDATION ON MOOSE: A REVIEW OF RECENT NORTH AMERICAN STUDIES AND THEIR MANAGEMENT IMPLICATIONS

Abstract

Predation of moose (Alces alces) calves by brown bears (Ursus arctos), black bears (Ursus americanus), and wolves (Canis lupus) singly or in combination can significantly limit annual recruitment. Brown bears are often the greatest source of mortality to calves where bear densities exceed 16/1,000 km², even though black bears maybe 2-3 times more abundant. Black bears are the largest source of moose calf mortality when they are 10 times more numerous than brown bears and their densities are >200/1,000 km². minimum average predation by brown bears on neonatal moose ranges from 1 calf/7-12 bear-days in late spring and early summer. Minimum prediction rates by black bears on neonatal moose ranged from 1 calf moose/11-53 bear-days. Predation rates on moose calves by grizzly bears appear to be independent of moose density while black bear predation rates may be related to moose densities and occurrence of brown bears. Brown bears can be significant predators of adult moose averaging 1 kill/26-102 bear-days. Black bears are not significant predators of adult moose. During 1 study when brown bear populations were temporarily reduced by >60% calf and adult moose survival increased in the short term. Effects on moose population of lesser bear reductions are unclear and warrant further study. If predator populations must be reduced to favor ungulate populations managers should first reduce wolf or black bear populations that have higher reproductive rates, wider geographic distributions, and are easier to manage than grizzly bear populations.