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November 1, 2022

As sea ice declines, more polar bears are coming onshore each summer and staying longer, increasing the potential for more human-bear interactions.

ANCHORAGE, Alaska – As Arctic sea ice continues to decline, the amount of time polar bears spend onshore has grown significantly, according to a new study published by the U.S. Geological Survey.

Researchers assessed the past, present and future summer movement of polar bears in Alaska and Russia between 1985 and 2040 to get a better understanding about how declining sea ice alters the bears’ behavior, particularly how it affects their time spent on land.

“Back in the 1980s, polar bears would only spend a couple of weeks onshore each summer,” said Karyn Rode, a USGS Research Wildlife Biologist. “However, now many spend nearly two months ashore each year.”

Rode and a team of scientists from the USGS Alaska Science Center and the U.S. Fish and Wildlife Service Marine Mammal Management Office used radio tracking data from Alaska’s two polar bear subpopulations, the Chukchi Sea and Southern Beaufort Sea, to forecast trends in land use during summer.

Based on recent observations, there has been an increase in the number of bears summering onshore (from around 5 percent to upwards of 50 percent of the population) and the time spent on land (from around 20 days to 60-70 days). Factoring in future climate predictions, researchers expect sea ice to continue declining, leading to more than half the bear population spending upwards of three to four months on land each year by 2040.

“Historically, polar bears spent most of their lives out on the ice where they would hunt for seals,” said David Douglas, a USGS Research Wildlife Biologist. “However, in recent years, an increasing number of bears have come ashore during the summer when sea ice is scarce, leading to them spending much more time in areas used by people.”

The research highlights the potential for a seasonal shift in where polar bears will be, with bears spending more time along coastal areas where they may be closer to people. The amount of time polar bears spend on land can have major implications for their nutritional needs, interactions with other wildlife and for the management of human-bear conflict.

Scientists and land managers can use the study’s findings to help improve monitoring of the bears and plan better ways to protect people from possible future bear encounters.

The study was published in the journal, Global Ecology and Conservation: https://doi.org/10.1016/j.gecco.2022.e02319

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