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Trophy Points: Big Game Research Online -- Part 2
Tuesday, May 26, 2009

Fact Stranger Than Fiction: Bears Afraid of Deer?

In most instances, a confrontation between a white-tailed deer and a black bear would be decided in favor of the bear. Dr. Steve Côté, a scientist with the Université Laval in Quebec, has indentified a situation which defies this conventional wisdom. Dr. Côté and his colleagues have been studying white-tailed deer on Anticosti Island, a 3,000-mile island in the Gulf of St. Lawrence in Quebec. Until the late 1800s black bears and mice were the only herbivorous mammals on the island. Bears were abundant in large part because of large, diverse berry crops. In 1896, 200 white-tailed deer were released on Anticosti Island and in 30 years their numbers had increased to over 50,000.

For some period after the introduction, bears probably benefitted from the white-tailed deer, learning to catch fawns in the spring and feeding on deer carcasses when they were available. However, as the years passed, bears begin to have difficulty finding enough food in autumn to acquire the fat stores necessary to hibernate through the long cold winters. Bears are particularly sensitive to a decline in autumn food because pregnant females give birth in February while in their dens. Sows nurse their cubs for up to 3 months before emerging. Thus, for bears to reproduce, females must not only acquire sufficient reserves to ensure their own survival over winter, but they must store enough fat to support the growth of their cubs.

Deer relish berries, and they also like the bushes that produce berries. For this reason berry bushes, not to mention berries, are rare on Anticosti Island now. Black bears are no longer found on the island, despite their populations doing remarkably well in nearly all other portions of their range. All indications are that overabundant deer, perhaps topping 100,000 in recent decades, extirpated black bears from the island.

What does this mean to those interested in wildlife management and conservation?

  • A simple action, like releasing 200 deer onto an island, can have far reaching implications.
  • Failure to manage the abundance of one species can decimate others.
  • Conventional wisdom cannot always predict outcomes in the natural world. In some circumstances, bears should live in fear of deer.

For more information see Extirpation of a Large Black Bear Population by Introduced White-tailed Deer by Steve Côté, Conservation Biology 19:1668-1671.


Trophy Points: Big Game Research On Line is complied and edited by David G. Hewitt, a Professional Member of the Boone and Crockett Club and the Stuart W. Stedman Chair for White-tailed Deer Research at the Caesar Kleberg Wildlife Research Institute.

 


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