[ad_1]
- Scientists believe that whale carcasses may have helped polar bears survive during the temperature rises that melted the pack ice where they usually hunt seals.
- While current climate change threatens to free the Arctic from ice during the summer, this strategy could help some polar bear populations survive.
- But according to a new study, whale carcasses will not provide enough food for most bears because there are fewer whales than before, and human settlements, industry and shipping could affect bear to all carcasses washed on the ground.
Dead whales are a nutritional boon to polar bears and have probably helped bears survive during the lean season during the warmer summer months when much of the Arctic was ice-free. However, in the future, most bears will not have that chance, writes a team of scientists in the newspaper Borders in ecology and environment October 9th.
"[When] We are looking at the current ecological situation with respect to food sources. It's a very different picture, "said Ian Stirling, a biologist at the University of Alberta in Canada and co-author of the paper. "The potential of whale carcasses to bail out may still be significant in some areas, but, quite simply, their overall availability will be considerably less than before the Arctic invasion by humans."
Polar bears (Ursus maritimus) depend on sea ice, which allows them to hunt for seals, their main prey. But as the climate warms, sea ice disappears and ice-free arctic summers could become a reality by 2040.
At the present time, when warmer temperatures are cutting off Arctic ice, some bears are racing quickly until ice recurs, unless they encounter another source of ice. food. For example, a whale carcass that lands on land is an excellent source of fat and protein, and scientists believe that this strategy may have helped polar bears weather past temperature spikes.
"I think it's probably one of the most likely explanations of how polar bears have managed to get through the previous hot interglacial periods," Stirling said.
The carcass of a bowhead whale (Balaena mysticetus), weighing perhaps 100 metric tons (110 tonnes) can provide the bear with about the same amount of food as 1,300 ringed seals (Pusa Hispida), write the authors. Such a manna can feed dozens of bears, sometimes for years.
But enough whales wash themselves to support polar bears? Stirling and his colleagues wanted to know. They estimated that a population of 1,000 polar bears would need about 28 whales to die, float on the surface and wash themselves on land each year to meet their caloric needs. In a place like the Chukchi Sea, north of the Bering Strait between Russia and Alaska, the numbers of bowhead whales and gray whales are stable (Eschrichtius robustus), the team discovered that there were enough who would die and land to support as many polar bears.
"Cleaning the carcasses of large whales is probably important for bears in some areas and could protect them from the loss of sea ice," said Kristin Laidre, marine biologist at the University of Washington and senior author of the # 39; study.
"However, carcasses of large whales are not expected to replace seals as a nutritional resource as we move towards an ice-free Arctic," added Laidre. "In most areas, environmental changes are too big and there are too few whale carcasses."
Most bear subpopulations do not live in areas where so many whale carcasses appear each year. The number of whales was much higher than before the whaling of the last centuries. And where they are washed, the carcasses are valuable to polar bears only if they can find them and if they are not prevented from traveling by human settlements, industry or shipping.
These complicating factors mean that the opportunistic strategy that has helped polar bears survive in ice-free periods in the past may not work in the decades to come.
"If the rate of sea ice loss and warming continues unambiguously, what will happen in polar bear habitat will surpass everything that has been documented over the past few million years." 39 years, "said Laidre. "The extremely fast pace of this change makes it almost impossible to use history to predict the future."
Polar banner image feeding on the carcass of a fin whale in Norway by Daniel J. Cox / Arctic Documentary Project.
Quote
Laidre, K.L., Stirling, I., Estes, J.A., Kochnev, A. and Roberts, J. (2018). The historical and potential future importance of large whales as food for polar bears. Borders in ecology and environment.
FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do it at the bottom of the page.
[ad_2]
Source link
