New Study Suggests Hudson Bay Polar Bears Could Die Out in the Coming Decades
14.07.2010 - Water & Oceans, Ice & Snow, Flora & Fauna, Arctic
Hudson Bay polar bears may be running out of time, a recent paper in Biological Conservation suggests. Basing themselves upon the extensive available data, researchers from the University of Alberta have tried to figure out how long before western Hudson Bay’s polar bears disappear. Comparing the data to projected sea ice declines, the team estimated that they might die out in the next 25 to 30 years.
One of the major issues the researchers highlighted is the gradual decline in body condition, which started in the 1980s. There is a significant correlation between their change in morphology and the retreat in sea ice. In the 1980s, polar bears spent close to eight months a year on the ice, where they had plenty to eat, and spent four months a year on land where they fast. Over the last three decades an average of one extra week per decade has been added to the time they must spend on land fasting.
The problem, the study says, is the energy the bears have drives many of their activities, including reproduction. Pregnant females rely on the amount of fat that they’ve been able to store to produce cubs, and fat females have been shown to produce more twins and triplets than their skinny counterparts, who either forego reproduction altogether or give birth to smaller cubs.
Besides the drop in birth rates, the increased number of days on land could cause a major increase in mortality rates. Depending on the length of the sea ice-free period, there could be 30% annual mortality rates of adult males, and even higher rates for females and cubs. Moreover, the impact of receding sea ice and larger areas of open water could hamper the ability of males and females to find one another and mate, which could result in a plummeting pregnancy rate for females.
A further concern is that what’s happening in Hudson Bay could be replicated further north as the Arctic warms. So far, however, other polar bear populations in more remote areas appear to be doing well.
