Polar Bears On The Western Coast Of The Hudson Bay In Nov. 2011 Vs. Nov. 2012

By Ian Stirling, Daryll Hedman, and Vicki Trim

In late fall, polar bears in the Western Hudson Bay subpopulation accumulate along the shoreline waiting for freeze-up so they can return to the sea ice, which is the critical platform they need for hunting seals. Following breakup of the sea ice several months earlier, there is no ice on Hudson Bay so the bears have not had much to eat. Instead, they have to survive on whatever fat reserves they accumulated before the sea ice melted.

However, for the polar bears of western Hudson Bay, the average date of breakup is now a full 3 weeks earlier than it was only 30 years ago! The reason this change is so critical is that late spring and early summer is the period when the greatest numbers of fat, newly weaned ringed seal pups are available, and are probably easier to catch because of being less experienced with polar bears. The bears take on an estimated two-thirds or so of the energy they will need for the entire year during the spring feeding period prior to breakup. Thus, it is a double whammy for the bears – not only are they unable to access seals in the open water, but they also lose the ice platform they need for hunting at the most important time of the year for feeding. Then, they have to survive for longer and longer periods with less stored fat because freeze-up in the fall is becoming later as well.

Read more on the Polar Bears International website.