Researching the Effects of Climate...

Researching the Effects of Climate Change on the Polar Bears of Southern Hudson Bay

by Canadian Wildlife Federation
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As I sit comfortably in my warm office in Toronto writing this post, the polar bears of the Southern Hudson Bay subpopulation are out on the frigid sea ice in the middle of Hudson Bay and James Bay looking for seals. Food is relatively plentiful for polar bears this time of year, and with so many adaptations that allow them to live in this Arctic marine habitat, these winter conditions suit the bears just fine. Mother polar bears of this subpopulation are warm in their dens along the northern coast of Ontario, having just given birth to their cubs. After a few months of nursing the tiny dependent newborns, these family groups will leave their dens to head out on the ice where the mother polar bears will catch as many seals as they can to feed their young families before the ice breaks up in the summer. All of the Southern Hudson Bay polar bears are then forced to retreat to the northern Ontario coastline or islands of James Bay to fast and await the return of the ice next winter. Because the life history of the polar bear is so intrinsically tied to the sea ice, the recent weakening of the Hudson Bay annual sea ice through the effects of climate change will have dire consequences for this population of polar bears that lives at the southern extent of the species range.

This year represents the first of a three year project through a partnership between York University and the Ontario Ministry of Natural Resources to study the effects of a changing climate on the feeding habits of the Southern Hudson Bay polar bears. We completed our first field season this past fall, handling polar bears along the shore of Akimiski Island and the western shore of James Bay. We had a very successful field season, deploying ten GPS collars on adult female polar bears and collecting important biological samples and morphometric information from a total of 36 bears. My PhD supervisors Dr. Gregory Thiemann and Dr. Martyn Obbard are experienced polar bear biologists, but this was my first time getting hands on experience studying polar bears. It was an amazing experience getting to appreciate the sheer size and power of these animals up close. The bears we handled ranged from young subadults spending their first fall apart from their mothers, to large, stoic adult males tipping the scales at over 1,200 pounds! We certainly encountered a wide range of bears, including pregnant females in excellent body condition who were preparing to enter dens later in the season, as well as mothers with dependent cubs who were quite thin from the added stress of feeding their young.

The range in individual polar bear size and condition is really quite striking, and ties in closely with our research which will compare the feeding habits of different classes of polar bears based on age, gender, and body condition. By determining the food habits of individual polar bears and linking this information with movement patterns of bears equipped with GPS collars, we will increase our knowledge on the specific types of sea ice habitat polar bears exploit. By combining this information with future predictions of sea ice extent and prey availability in Hudson Bay, we will contribute to ensuring that informed and proper conservation measures are taken in the future. Through the support of the Canadian Wildlife Federation Endangered Species Fund, this important research will help in predicting the future of polar bears in this region, as the challenges currently faced by the bears by an extended ice-free season are forecasted to intensify in the coming decades.

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