Polar bear diet changes as sea ice melts

Posted By News On January 22, 2014 - 3:00pm
Polar bear diet changes as sea ice melts

A series of papers recently published by scientists at the American Museum of Natural History suggests that polar bears in the warming Arctic are turning to alternate food sources. As Arctic sea ice melts earlier and freezes later each year, polar bears have a limited amount of time to hunt their historically preferred prey—ringed seal pups—and must spend more time on land. The new research indicates that at least some polar bears in the western Hudson Bay population are using flexible foraging strategies while on land, such as prey-switching and eating a mixed diet of plants and animals, as they survive in their rapidly changing environment.

"There is little doubt that polar bears are very susceptible as global climate change continues to drastically alter the landscape of the northern polar regions," said Robert Rockwell, a research associate in the Museum's Department of Ornithology. "But we're finding that they might be more resilient than is commonly thought."

Polar bears are listed as a threatened species under the United States Endangered Species Act and are classified as "vulnerable" with declining populations on the International Union for Conservation of Nature and Natural Resources' Red List. Climate warming is reducing the availability of their ice habitat, especially in the spring when polar bears gain most of their annual fat reserves by consuming seal pups before coming ashore for the summer. The new work, led by Rockwell and Linda Gormezano, a postdoctoral researcher in the Museum's Division of Vertebrate Zoology, examines how polar bears might compensate for energy deficits from decreasing seal-hunting opportunities.

A polar bear, Ursus maritmus, eats a caribou.

(Photo Credit: ©American Museum of Natural History/R. Rockwell)

In the first paper, published in spring 2013 in the journal Polar Ecology, the researchers provide, for the first time, data and video of polar bears pursuing, catching, and eating adult and juvenile lesser snow geese during mid-to-late summer, when the geese are replacing their primary flight feathers.

In the second paper, published in summer 2013 in the journal Ecology and Evolution, researchers used polar bear scat to show that the diet of at least some of the bears has shifted from what it was 40 years ago, before climate change was affecting the Hudson Bay lowlands. Today's polar bears are preying more on caribou as well as on snow geese and their eggs.

In the final paper in the series, published in December 2013 in the journal BMC Ecology, the researchers show that polar bears are, with a few exceptions, consuming a mixed diet of plants and animals. The predominance of local vegetation in collected scat suggests little movement among habitat types between feeding sessions, indicating that the polar bears are keeping energy expenditure down.

This is Quinoa, a Dutch shepherd trained to sniff out polar bear scat.

(Photo Credit: ©American Museum of Natural History/R. Rockwell)

Taken together, the research indicates that during the ice-free period, polar bears are exhibiting flexible foraging behavior. This behavior likely derives from a shared genetic heritage with brown bears, from which polar bears separated about 600,000 years ago.

"For polar bear populations to persist, changes in their foraging will need to keep pace with climate-induced reduction of sea ice from which the bears typically hunt seals," Gormezano said. "Although different evolutionary pathways could enable such persistence, the ability to respond flexibly to environmental change, without requiring selective alterations to underlying genetic architecture, may be the most realistic alternative in light of the fast pace at which environmental changes are occurring. Our results suggest that some polar bears may possess this flexibility and thus may be able to cope with rapidly changing access to their historic food supply."

Quinoa, a Dutch shepherd, sniffs for polar bear scat on an ice flow.

(Photo Credit: ©American Museum of Natural History/L. Gormezano)

Well ; this observation that Polar Bears are indeed well adapting to the Climate Change by dynamically - flexibly changing their diet to the land based foods ` Snow Geese, Eggs and Caribou ` was in fact predicted long ago by their(polar bears) genetic`evolutionary` history since they presumably diverted from other bears 110-130,000 years ago (* ) ,in 2007 , 23 cm Jaw bone may be the oldest known remains of a polar bear have been uncovered on the Svalbard archipelago in the Arctic and mitochondrial DNA and phylogenetic tree of Polar and other Bears is established since then . So it was not that long ago they diversified from each other ; it means they can go back and forth easily to adapt the changing environment like other bear species relatives .
But the significance of the observation that Polar Bears will likely to survive without any difficulty to the Climate Change ( It really does NOT matter what is the underlying `true` cause and effect of Climate Change ) whether it is : a- Sun`s radiant solar radiation heat change coming to the earth OR b- Galactic cosmic radiation high cloud formation change due to galactic cycle OR c- so called `Fossil fuel` burning and green house effects and resultant CO2 concentration change (which is blaming humans for burning fossil fuel and intending to change `energy policy` ) exactly like `ancient priests` blamed humans for the celestial events thousands of years ago so they can change their behavior by spreading unfounded fear –nothing has changed of course in the dynamics - except ancient priests replaced with fake scientists with dubious energy policy change and economical agendas in their mind , rather than `true science`.
Of course the observational research data mentioned here ; that Polar Bears are indeed well adapting to the climate change `that means we do not have to worry about their(polar bears) survival and immediate extinction ` . But ; – fake /ancient priest like scientists – losing very important and big ` verbal and laud crowd of support ` animal loving allies ` that they have been effectively manipulating by using various promotional `propaganda clips` regarding climate change will harm/and even extinct the Polar bears ; now that presumption is not valid anymore false assumption that Polar Bears solely dependent on ice for their survival .
(* ) http://news.bbc.co.uk/2/hi/7132220.stm

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