Published: Sun, February 04, 2018
Medicine | By Rogelio Lindsey

Polar bears struggling to catch enough seals as ice fades

Polar bears struggling to catch enough seals as ice fades

As human-produced greenhouse gas emissions continue to fuel global warming, the Arctic sea ice levels continue to shrink by about 13.2 percent per decade.

USGS researchers have been studying polar bears in the Beaufort Sea area since the 1980s and have found that polar bear population has declined by 40 percent in the past decade.

"We found a feast and starvation lifestyle - if they missed out on seals it had a pretty dramatic effect on them", said Anthony Pagano, a USGS biologist who led the research, published in Science.

But understanding the exact relationship between the loss of ice and the plight of the polar bear has been a little murky because it's hard to track the movements of these enormous apex predators in remote regions.

Pagano, who is also a wildlife biologist with the U.S. Geological Survey (USGS), conducted the study as part of his Ph.D. thesis research at UC Santa Cruz, where he has been working with coauthors Terrie Williams and Daniel Costa, both professors of ecology and evolutionary biology. But some populations have seen sharp declines, while other researchers have found bears in some communities are smaller and less heavy than they used to be, he said.

LONDON-High-tech tracking collars on nine female polar bears have measured the animals' efforts to find food on the diminishing Arctic ice. These trackers included accelerometers and GPS-equipped video cameras to document the bears' activities.

During the test, researchers saw about half of hunting bears lost 10 percent of their body weight in just over a week. That helps the bear to gather a lot of fats and help them to survive more a long time without any foods.

While summer is a feasting period for other bear species, for polar bears it is a time of hunger.

The bears' metabolic rate was more the 50 per cent higher than previous studies had suggested.

"This was at the start of the period from April through July when polar bears catch most of their prey and put on most of the body fat they need to sustain them throughout the year", said Mr Pagano.

Polar bears rely nearly exclusively on a calorie-loaded diet of seals. Getting stuck on land simply wouldn't keep these apex predators alive.

Climate change is preventing polar bears from catching enough prey to meet their needs, with melting ice forcing them to expend excessive amounts of energy to track down seals, a study has found.

Millions have seen the heart-wrenching video of a polar bear clinging to life, its white hair limply covering its thin, bony frame.

"However", the authors wrote, "this rate of consumption would be necessary simply to energetically break even".

Polar bears could be sliding towards extinction faster than previously feared, with the animals facing an increasing struggle to find enough food to survive as climate change steadily transforms their environment. "That has a cost, and the animal has to find the energy to do that - or take it out of growth, reproduction, or survival", says polar bear biologist at the University of Alberta in Edmonton, Canada.

The new study also gave an idea how they hunt. Because of the video footage, the researchers know that these bears gained weight because they caught seals.

They concluded that a female polar bear must eat a fully grown seal every 12 days to meet its energy requirement.

Five of the bears were recorded losing weight during the study.

But as the global temperature is rising, polar bears can face more trouble in future. Further research will be needed to fully understand the impact of what is happening to the polar bears.

Like this: