Reply #5: So, the logical question is, “Why the apparent increase?” [View All]

[OKIsItJustMe]

Is this unusual, or is it just increased awareness on our part?

Is it a form of population control on the bears’ part? (are mothers doing a worse job of defending their cubs?)

http://animal.discovery.com/news/ap/20060612/polarbears.html

Study: Polar Bears Turning to Cannibalism

By Dan Joling, Associated Press

June 14, 2006 — Polar bears in the southern Beaufort Sea may be turning to cannibalism because longer seasons without ice keep them from getting to their natural food, a new study by American and Canadian scientists has found.

The study reviewed three examples of polar bears preying on each other from January to April 2004 north of Alaska and western Canada, including the first-ever reported killing of a female in a den shortly after it gave birth.

…

Polar bears kill each other for population regulation, dominance, and reproductive advantage, the study said. Killing for food seems to be less common, said the study's principal author, Steven Amstrup of the U.S. Geological Survey Alaska Science Center.

"During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears," the scientists said.

…

http://alaska.usgs.gov/science/biology/polar_bears/unusual_mortality.html

Mortality

• http://alaska.usgs.gov/science/biology/polar_bears/unusual_mortality.html#cannibalism">Observations of intraspecific predation by polar bears in the southern Beaufort Sea

Observations of intraspecific predation by polar bears in the southern Beaufort Sea

Intraspecific killing has been reported among polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus). Although cannibalism is one motivation for such killings, the ecological factors mediating such events are poorly understood. Between 24 January and 10 April 2004, we confirmed three instances of intraspecific predation and cannibalism in the Beaufort Sea. One of these, the first of this type ever reported for polar bears, was a parturient female killed at her maternal den. The predatory bear was hunting in a known maternal denning area and apparently discovered the den by scent. A second predation event involved an adult female and cub recently emerged from their den, and the third involved a yearling male. During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears. We hypothesize that nutritional stresses related to the longer ice-free seasons that have occurred in the Beaufort Sea in recent years may have led to the cannibalism incidents we observed in 2004.

http://www.springerlink.com/content/m518018263874231/?p=9712b15921b54ad8b63d762945e9a782π=9">Amstrup, S. C., I. Stirling, T. S. Smith, C. Perham, and G. W. Thieman. 2006. Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea. Polar Biology, 29:997-1002.