New videos about Polar Bears

Trekking the pack ice / Courtesy Patrick Kelley, U.S. Coast Guard

July 21, 2015— Listen: intense noises sound when Alaska’s polar bears gather to feed at a whale bone pile. At Frontier Scientists new discoveries in the Far North unfold on your screen.

In new videos Hair Reveals Diet and In the Eyes of the Polar Bear, Frontier Scientists features current polar bear research. Scientists Todd Atwood, George Durner, Matt Rogers, and Jeff Welker share their work investigating how sea ice habitat changes and hunting strategies impact polar bear reproduction, health and survival.

Courtesy Susanne Miller, USFWS

Shrinking hunting habitat

“Polar bears evolved as a predator of ice seals and so their survival is heavily tied to the sea ice,” explained George Durner, research zoologist with the United States Geological Survey Alaska Science Center. “But we also know,” Durner added, “Based on the record of satellite imagery beginning in the late 1970’s that sea ice has changed considerably as a result of climate warming, particularly in the Arctic.”

Polar bears he studies benefit by hunting on sea ice above the continental shelf region located close to Alaska’s northern shore. There, healthy plants and fish make for fat seals, and fat seals make good meals. In contrast “Deep water areas are generally not very productive,” Durner said, containing “Relatively few prey compared to the continental shelf regions.” That’s a problem.

“In more recent years because the sea ice melt has been so extensive, the amount of that preferred habitat has shrunk extensively.” Durner described during warmer summer months polar bears in Alaska have been “Displaced from the region they prefer because there was no sea ice there. The majority of the bears followed the sea ice north, hundreds of miles from the Alaska coast,” expending energy on long treks or long swims, while “A smaller subset of the population was stuck on land.”

Todd Atwood, research biologist and project leader for the polar bear research program at the United States Geological Survey Alaska Science Center, noted “We still have pretty good sea ice habitat available for polar bears in the winter but it’s available for a shorter and shorter amount of time each year.

He asked: “If they will be on shore for extended periods of time because sea ice is unavailable, will they be able to find enough food to sustain themselves?” How will new strategies impact polar bear populations?

Whale bone piles

There are three communities that whale along Alaska’s north shore; Atwood explained “What they don’t use for subsistence purposes they aggregate into bone piles.” The bone piles attract polar bears. “You can see aggregations of up to 80 polar bears a day visiting the bone pile in Kaktovik,” foraging for food.

“We’ve tried to capitalize on that,” Atwood said. “We string a strand of barb wire around the Kaktovik bone pile.” Barbs snag hair from bears moving past, granting scientists upwards of 500 samples a year. Atwood calls it a “Simple, non-invasive way to collect samples from bears.” The samples are sent to the lab to be analyzed, giving “A genetic fingerprint of all the different bears that visit the bone pile.”

Matt Rogers, research scientist at the University of Alaska Anchorage, runs the day-to-day operations of the Stable Isotope Lab. The lab deals with collected polar bear hairs, which are cut into minuscule segments, each representing about a month of polar bear diet.

Courtesy Steve Hillebrand, USFWS

Nitrogen clues

Rogers noted as polar bear hair grows “It locks in the signature, the isotope signature of whatever they are eating at the time. And that is preserved in the hair for as long as that hair is on the body.”

The isotopic signature describes nitrogen that a bear acquires by eating. Most nitrogen atoms have 14 neutrons, but some nitrogen atoms have 15 neutrons instead. With more neutrons in the nucleus the atoms are heavier. “When the polar bear metabolizes the nitrogen, the heavy isotope of nitrogen acts a little bit differently than the light isotope.”

“If the bear is eating a lot of seal, we see the heavy nitrogen that gets incorporated into the hair.” Seals, high on the food chain, have incorporated a lot of heavy nitrogen in their muscles. In contrast lower- food chain animals like bowhead whales have less heavy nitrogen. What a polar bear eats leaves a mark; by analyzing hair segments scientists can map out a polar bear’s diet month-to-month.

Jeff Welker, professor of Ecology in the Department of Biological Sciences at the University of Alaska Anchorage and Fulbright Distinguished US Arctic chair to Norway, reported what the hair helped scientists discover.

While most bears still primarily hunt and eat seals, traveling the sea ice, there’s “A group of bears that spend time closer to the shore and pretty much in the Fall on a regular basis are using these whale bones as a secondary diet resource,” said Welker. “The availability of intact sea ice which supports these seal populations is becoming less and less and it appears that the bears are being opportunistic in taking advantage of other resources that are out there.”

That’s part of the core of what this science is about. Atwood reported: “We are interested in how changes in the physical environment, mainly the deterioration of the sea ice ecosystem, is causing changes in individual and population health.”

Thanks to polar bear images contributed by Polar Bears International and by Daniel J. Cox of Natural Exposures.

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