Canadian polar bears turning to cannibalism in Hudson Bay

I was born in a coal-mining town in England, and was trained as a scientist, especially in marine animal ecology. The well-worn references to, and use of, the “canary in the coalmine” reflected very hard-learned lessons from past generations of miners in my birth-town. Better to read the signs in the canary in its cage 100 ft underground than to keel over yourself as carbon monoxide or other gases built up then poisoned you and your fellow miners.

In the last few days the polar bears in western Hudson Bay, Canada, the best-studied subpopulation among the 19 across their Arctic range, have been giving us a dramatic and stunning new signal of population stress – at least 10 reported cases now of cannibalism, primarily the killing of cubs by adult males for food. Three decades of intensive polar bear studies here have hardly ever recorded such cannibalism. This is very new, and dramatic. The Nobel prize-winning IPCC team of 3000 world class scientists used this polar bear subpopulation and its responses to declining sea-ice coverage as an important signal in their assessments and modeling of the impacts and projections of/for rapid climate change. As an ecologist, I know that these are great studies over the past 30 years, and that the trends of key population parameters (declines in cub survival, recruitment, adult survival, body condition, and eventually total population estimate) are familiar to any animal population experiencing major stress. It’s not specific to polar bears; most species when experiencing major habitat or population stresses respond in just these ways. That is the forces of nature at work. That’s why the miners used the little canary in its cage.

It’s December now, and to the amazement of local people and polar bears, and even cautious Arctic scientists, the sea ice has not yet returned to Hudson Bay! It’s late, very late, and so the polar bears who have spent the past five months or so along the coastline without significant fat-rich food, waiting for their sea-ice platform to return, are forced to wait even longer. It’s likely that the hungriest, skinniest individuals are starving and becoming desperate…. starting the risky behavior of preying on younger bears. That sea-ice used to be back in early November, then the bears all headed out quickly to catch ringed seals. Polar bears cannot survive on seaweed, berries or dried grass. They are top carnivores, evolved on a high fat diet. They have no option but to catch marine mammals from a stable sea-ice platform. No ice ultimately means no polar bears; it’s as simple as that. And our inattention to the GHG problem is thinning and shrinking of the global sea-ice at unprecedented rates.

The big question now is whether Canada’s leaders are reading these signs, and whether these urgent alarm bells rung by the polar bear will be heeded as heads of state gather in Copenhagen to make decisions that will take care of GHG emissions, and hence the future of not only polar bears and sea-ice, but also the stability of our planet’s climate patterns and economies. Perhaps the coal-miners could teach some of the world’s leaders a few fundamental lessons about the need to pay serious attention to such biological signs, and then to take very quick actions in response!

Peter J. Ewins, D.Phil.
Senior Officer, Species
Arctic Program