A male polar bear carries the head of a polar bear cub it killed and cannibalized in an area about 300 km (186 miles) north of the Canadian town of Churchill November 20, 2009. Climate change has turned some polar bears into cannibals as global warming melts their Arctic ice hunting grounds, reducing the polar bear population, according to a U.S.-led global scientific study on the impacts of climate change. Credit: REUTERS/Iain D. Williams
There has been recent coverage on cannibalistic behaviour of the polar bears (Ursus maritimus). On December 2009, it was reported in The Times that the climate change is ‘forcing polar bears to become cannibals’ (http://www.timesonline.co.uk/tol/news/environment/article6949625.ece). According to climate change campaigners, the increasing cases of polar bear cannibalism is attributed to the melting of ice and slow ice formation, leading to a decrease in platform from which to hunt seals. However, Inuit leaders (indigenous people inhabiting the Arctic regions) has classified the polar bear cannibalism occurrence as normal.
This uncommon animal behaviour has been seen before and is not the first time being documented. As early as 1985, possible cannibalism by polar bears have been recorded. It is usually the adult male that kills the young while the female tries to defend them. It was found that cannibalism among polar bears does occur under natural conditions (Lunn & Stenhouse, 1985). The reason for such occurrences are still unknown but several reasons have been suggested to explain these actions.
The initial speculation was that the adult male killed young polar bears so that the mother will breed with him. However, the male showed no interest in the adult female after the event which led to the conclusion that the killing was simply for food. Interestingly, it has been observed that the polar bears who cannibalize do not appear to be malnourished. Subsequent studies believe that infanticide may be a density dependent parameter in polar bear populations. Infanticide may be a form of population control but it does not explain the need to cannibalize on the dead cubs. There are also suggestions that geographic features play a part (Derocher & Wiig, 1999).
The reasons stated do not provide a satisfactory answer to the cannibalistic behaviour of polar bears. Although it is a natural occurrence, the climate change in contemporary world cannot be completely ruled out. To better understand the complex interacting factors of such events, more direct observational data is needed (Dyck & Daley, 2002).
A male polar bear drags the remains of a polar bear cub it killed and cannibalized in an area about 300km (186 miles) north of the Canadian town of Churchill November 20, 2009. Credit: REUTERS/Iain D. Williams
References
Lunn, NJ & Stenhouse, GB. (1985). An observation of possible cannibalism by polar bears (Ursus maritimus). Canadian Journal of Zoology/Revue Canadienne de Zoologie [CAN. J. ZOOL.]. Vol. 63, no. 6, pp. 1516-1517.
Derocher, A.E & Wiig, Ø. (1999). Infanticide and Cannibalism of Juvenile Polar Bears (Ursus maritimus) in Svalbard. ARCTIC Vol. 52, No. 3 P. 307–310 http://pubs.aina.ucalgary.ca/arctic/arctic52-3-307.pdf
Dyck, M.G & Daley, K.J. (2002). Cannibalism of a Yearling Polar Bear (Ursus maritimus) at Churchill, Canada. ARCTIC Vol. 55, No. 2 P. 190–192 http://pubs.aina.ucalgary.ca/arctic/arctic55-2-190.pdf