Walruses in the Chukchi Sea during a tagging survey onboard the Norseman II in June 2010.

A just-released USGS film will take you on a journey along with USGS researchers tracking walruses going about their daily lives in the remote Chukchi Sea. The film, Tracking Pacific Walrus: Expedition to the Shrinking Chukchi Sea Ice, follows scientists as they travel to the Chukchi Sea to examine how these mammals are faring in an Arctic environment with sparse summer sea ice and increased human activity.

The USGS-produced film contains exclusive footage of the large mammals in their natural habitat, documenting the lives of these huge animals as they raise their young, dive for clams and worms on the ocean floor or congregate with other walruses.

A Changing Arctic Climate Means Changing Arctic Ecosystems

Arctic sea ice is melting faster than forecasted by many of the top climate models: the first ice- free summer is now predicted to occur by 2035, perhaps as soon as 2025.

But warming temperatures are causing other changes as well — increased coastal erosion, deteriorating permafrost, and major changes in the dynamics of freshwater flows. These changes influence biological communities and the ways in which human communities interact with them. For example, the longer open water season in the Arctic is allowing increased shipping, tourism, energy production and other human activities in this remote region.

As part of the USGS Changing Arctic Ecosystems initiative, USGS researchers are identifying and investigating the linkages among physical processes (such as sea ice melting at a faster rate), ecosystems and wildlife populations.  By understanding the degree to and manner in which wildlife species adapt to rapid environmental change, resource managers and policy makers will have a better foundation for making critical decisions now and in the future.

New Research on Pacific Walrus and Sea Ice

The information gained through tracking large marine mammals, such as polar bears and walruses, is helping USGS scientists understand how disappearing Arctic sea ice is affecting the region’s ecosystems and the species that inhabit these ecosystems.

Scientists prepare to radio-tag walruses in the Chukchi sea to track movements as sea ice is reduced in the region.

For example, recently published research by USGS and Russian scientists revealed that diminishing summer sea ice in the Arctic over the past 5 years has caused behavioral changes in Pacific walruses. The population-level effects of these changes are unknown and the subject of active investigation by USGS.

Using a simple darting system, scientists attached radio-tracking tags to 251 walruses in the Chukchi Sea. The tags transmitted the animals’ whereabouts and whether they were in the water and feeding. Using the tagging data gathered from 2008-2011, scientists created detailed maps of the walruses’ seasonal movements and feeding patterns relative to the location and amount of sea ice.

When Chukchi Sea Ice Retreats North of the Continental Shelf Edge, Walruses Haul Out

The study found that due to earlier melting of the ice in the summer, walruses arrived earlier in their northern feeding grounds on the broad continental shelf of the Chukchi Sea. When the sea ice over the continental shelf melted completely in the fall, however, they “hauled out” onshore in large aggregations and foraged for food closer to shore. [Hauling out refers to the behavior associated with seals and walruses of temporarily leaving the water for sites on land or ice.]

The specific effects of these behavioral changes are not yet understood; however, scientists do know that while onshore, young walruses are susceptible to mortality from trampling. USGS has recently published a study that examined the population effects of this type of mortality, finding that loss of young animals to haul-out mortality has a greater effect on the population than loss of adult females in the harvest.  In light of this finding, the U.S. Fish and Wildlife Service is increasing its ongoing efforts to protect hauled-out walruses from disturbance.

Additionally, hauling out onshore and using nearshore feeding areas may require more energy for animals used to simply diving off their sea-ice platforms for food at the bottom of the shallow Chukchi Sea.

Data from this study will provide resource managers with basic information on areas important for walruses, such as the Hanna Shoal region, as human activities in the Arctic increase. The areas of walrus foraging observed in this study overlap with oil and gas lease blocks leased by BOEM (Bureau of Ocean Energy Management).

Adult female walrus on ice floe.

The study, published as this month’s feature article in the journal Marine Ecology Progress Series, is part of the USGS Changing Arctic Ecosystems initiative at the Alaska Science Center.

Some Polar bears in the Arctic can swim in excess of 200 miles.

Polar bears spend much of their lives in and around water, and they are well adapted for swimming. But recent findings of USGS  scientists demonstrate that they are even better swimmers than many imagined: In years of extreme sea-ice retreat in the southern Beaufort Sea region of Alaska, polar bears have been documented taking very long swims,   in excess of 30 miles.

Data collected from long distance swims by Polar bears suggest that they do not stop to rest during their journey.

In addition to being an impressive feat, this provides some tantalizing clues into the polar bear’s future in an Arctic with less sea ice. That these bears can swim such long distances might mean that they are not as vulnerable to being stranded at sea as has been depicted by the media. Scientists wonder, however, if polar bears might be expending essential energy in swimming long distances.

A USGS-led study tracked 52 adult female polar bears outfitted with global positioning system collars from 2004 to 2009. Getting a satellite telemetry collar on a polar bear is no simple matter. Scientists use helicopters to fly over the sea ice to find and tranquilize bears. While the bear is tranquilized, scientists attach a radio collar with multiple antennae and give the bear a small identifying tattoo on the inside of the upper lip.

Later, when the bears are swimming, one of the antennae is submerged so that the swims appear as gaps in the data that is transmitted. Overlaying this data onto maps of sea ice shows scientists approximately where the bears are swimming. Researchers documented 50 swims with an average length of 96 miles. While long-distance swims were relatively uncommon, 38 percent of the collared bears took at least one long swim. Results from the study appear in the current issue of the Canadian Journal of Zoology.

Data collected from long distance swims by Polar bears suggest that they do not stop to rest during their journey.

Scientists have no way of knowing if long-distance swims are a new feature of polar bear life. “We did not have the GPS technology on collars to document this type of swimming behavior in polar bears in prior decades,” explains Karen Oakley, of the USGS Alaska Science Center . “However, summer sea ice conditions in the southern Beaufort Sea have changed considerably over the last 20 to 30 years, such that there is much more open water during summer and fall. Historically, there had not been enough open water for polar bears in this region to swim the long distances we observed in these recent summers of extreme sea ice retreat.”

While it is encouraging that polar bears can swim so far, it is also a potential risk for the bears, the researchers noted. The energy and physical costs of such long-distance swimming are unknown, but scientists did note polar bears moved, on average, 2.3 times more than when the same individuals were on sea ice. The movement data also suggest the bears were not pausing to rest or feed during long-distance swims. Twelve of the twenty documented swimming bears were adult females that had yearlings or cubs-of-the-year at the time they were outfitted with the GPS collar.

“We were able to recapture or observe 10 of these females within a year of collaring, and 6 of these females still had their cubs,” said Anthony Pagano, a USGS scientist and lead author of the study.  “These observations suggest that some cubs are also capable of swimming long distances. For the other four females with cubs, we don’t know if they lost their cubs before, during, or at some point after their long swims.”

Scientists track Polar bears with by attaching GPS equipped collars to a sample population. These collars transmit data that help develop maps like this one that shows a swim of nearly 220 miles long.

This and other USGS-sponsored polar bear research projects are aimed at refining and enhancing models to project the future status of polar bears in a rapidly changing Arctic environment in which sea ice is continuing to retreat faster than forecasted.