Polar bear expert and zoologist Susan Crockford is firing back today at recently published articles that say polar bears are somehow starving and “food deprived” because of global warming. The problem is that since 1979, polar bears are thriving and far from starving. This is due to plentiful Arctic sea ice they need (except when it’s too thick) to hunt for food before the summer arrives. Unlike most carnivores, polar bears are unique mammals that do all their primary feeding in the spring, and very little during the summer. Other mammals hunt and gather food in the late spring, summer, and fall, but because of the Arctic’s unique climate, late winter/spring is the time that polar bears hunt and fatten up.
According to Crockford, “polar bears are at their lowest weight in March and at their highest in June/July.” She notes that other large mammals don’t have this unique eating pattern because no other carnivore lives on the surface of the sea ice. “Summer is warm across the Arctic,” she writes. “It’s the perfect time for polar bears to fast, as little energy is needed for keeping warm, especially if they don’t swim around.”
She also notes the “polar-bears-are-doomed crowd can’t hide the fact that this year, spring sea ice habitat for polar bears worldwide has been excellent.” For example, Hudson Bay sea ice extent on July 19 this year was 150,000 square kilometers higher than in recorded on that date in 2009 (526.2 vs. 368.5 mkm2).
Norwegian polar bear researchers also reported a good crop of cubs this spring because conditions have been excellent for pregnant females around Svalbard. Worldwide, the amount of Arctic sea ice on July 18, 2015, was the same on that date in 2006, and by July 19, there was actually more sea ice than the same date in 2006 (8.4 vs. 8.3 mkm2).
Put simply, the recent summer ice melt has not interfered with the spring feeding period “that is so critically important for polar bears.” Leftover sea ice in early summer meant there was plenty of sea ice in the spring (April-June), even in the Southern Beaufort Sea. The only polar bear region with below-average sea ice extent over the last five years was the Chukchi Sea, but researchers have already shown that polar bears in that region are “doing very well even with no summer sea ice.”
Even though the Chukchi Sea currently has below-average summer sea ice, it doesn’t affect a polar bear’s eating habits, as fasting during the summer is normal for them. These Arctic carnivores put on hundreds of pounds of fat during the spring feeding period, chowing down on plump, plentiful young seals that are easy to catch, in preparation for the summer months. This time period, known as the “walking hibernation,” is likely an adaptation to their environment and not a physiological mechanism.
What all this means, Crockford writes, is that summer sea ice declines predicted in the Arctic “cannot possibly have any significant impact for otherwise healthy bears.” In 2012, this was evidenced by the record-breaking low September ice extent in the Southern Beaufort Sea that showed no noticeable effect on polar bear health or survival. Why? Summer ice extent has “nothing to do with polar bear health or survival.” Spring ice conditions are what matter most to all polar bear populations. It’s the time of year they spend fattening up for the upcoming summer.
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