A new study has found that polar bears cannot sustain themselves on a diet of bird eggs and berries instead of their traditional diet of seals and marine mammals. Scientists had wondered whether a land-based diet of caribou and berries could help the huge bears survive climate change, but it appears not, writes Becky Oskin for LiveScience.
Polar Bears: No calorific reward hunting on land
The findings were published in the journal Frontiers in Ecology and the Environment, and state that the calorie trade-off of switching to a land-based diet is not worth it for the polar bears. As the biggest bear on the planet, the polar bears burn so many calories searching for berries or hunting caribou that there is little overall calorific reward in these meals.
“A really large bear has high energetic costs when they get up to forage, and these [terrestrial] resources are typically lower in calories or widely dispersed,” said Karyn Rode, lead study author and a U.S. Geological Survey research wildlife biologist in Anchorage, Alaska.
The traditionally fatty diet of polar bears provides them with the calories, vitamins and minerals that they need, but their nearest geographic cousin, the Arctic grizzly, can barely find enough food.
Scientists watching developments closely
Polar bears spend around 85% of their time resting and fasting on land, whereas an Arctic grizzly is constantly foraging. Despite the fact that a few bears have been eating bird eggs, any widespread adoption of the practice would cause a huge decrease in the Arctic seabird population.
The amount of Arctic sea ice close to the shore has been decreasing due to global warming, particularly around late spring when polar bears traditionally hunt seal pups before retreating onto land for summer. The decreasing sea ice means the bears move to shore earlier in the season in some areas, meaning that they can hunt geese, eggs and caribou instead.
Warmer Arctic waters could also see the arrival of new species in the area, which present new hunting opportunities for the polar bears. The face of the Arctic is changing irrevocably and the polar bear is the most impressive symbol of the struggle against climate change.