A recent voyage by the National Geographic Explorer ship to the Arctic captured a female polar bear fighting a male for food. NBCNews.com's Dara Brown reports on the trip, which allowed experts to evaluate the environmental changes in the Arctic.
By Miguel Llanos, NBC News
Wildlife biologist Ian Bullock is a seasoned visitor to the Arctic, but even he was surprised by what he saw last month: a thin female polar bear, shadowed by her cub, trying to challenge a much bigger, stronger male for food.
That desperation, he feels, stems from the fact that the Arctic's summer sea ice — which polar bears using as floating stations from which to hunt seals — has been shrinking over the last few decades due to a warming Arctic, forcing polar bears into smaller areas and more intense competition. It wasn't much of a challenge, but it showed just how desperate she was, Bullock told NBC News on returning from his 10th straight summer cruise to the Arctic.
"If she cannot feed, she cannot suckle her cub; with a hungry cub it is even harder for her to hunt effectively, so from what I saw her last cub is at risk and ultimately so is she," he added. "This is why she was challenging a big male with food. She was hungry enough to take a big risk." "She was the thinnest female with cub I have ever seen," he said. "She had a single cub which implies she has already lost one other cub this year.
In a video filmed during the National Geographic Explorer cruise to the Arctic's Svalbard region, Bullock said it looks like that reduced ice is "really putting the bears under stress."
"The worst thing is when we've encountered bears, we've found them really packed in tight, in the last little areas of fast ice attached to land, or the last little patches of pack ice at sea," said Bullock, who served as a guide on the cruise ship. "And there they've been in competition."
Polar bears are listed as "vulnerable" and in decline by the International Union for Conservation of Nature, which estimates the population at no more than 25,000 across the Arctic.
The U.S., which has two Arctic regions where polar bears live, in 2008 listed its population as "threatened".
"It was T-shirt weather," Paul Berkman, an environmental science professor at the University of California Santa Barbara, told NBC News. Berkman noted two other major Arctic developments over the summer:Another expert on the cruise called the outside temperature "surprisingly warm."
That response is twofold, he adds: Arctic temperatures have warmed 2-4 degrees Celsius above the global average, and reduced ice removes huge amounts of reflective white from the sea and reveals a dark sea that absorbs heat.Berkman said the polar regions, and the Arctic in particular, show an "amplified response" to a warming climate ahead of other parts of the globe.
The sea ice is like "a giant mirror on Earth's surface" he said. "Without summer Arctic sea ice, more heat from the sun is absorbed into the Earth system, which is a feedback that further accelerates warming of our climate."