Warming Arctic climate constrains life in cold-adapted mammals

color photo of seven muskoxen on Wrangel Island

Muskoxen on Wrangel Island, located in the Arctic Ocean, between the Chukchi Sea and East Siberian Sea. Photo: Joel Berger

Despite the growth in knowledge about the warming Arctic, how such changes affect cold-adapted animal populations is poorly understood. Research efforts have been hindered by the area’s remoteness and the complex logistics required to study species in the field.

A new study led by Joel Berger, professor in the Department of Fish, Wildlife and Conservation Biology at Colorado State University, has uncovered previously unknown effects of rain-on-snow events, winter precipitation and ice tidal surges on the Arctic’s largest land mammal, the muskoxen.

The warmer climate is stressing mothers and young muskoxen, said Berger, also a senior scientist with the Wildlife Conservation Society. Rain-on-snow events and unusually dry conditions in the winter — when muskoxen gestate — have also led to underdeveloped skeletal growth in juvenile muskoxen.

close-up photo of a muskoxen in the snow in Alaska
Cold-adapted species like the muskoxen are feeling the heat. said wildlife biologist Joel Berger. Photo: Joel Berger

“When rain-on-snow events occur in the Arctic, due to warming temperatures, and the snow freezes again, this leads to mothers not being able to access food for adequate nutrition,” said Berger. “The babies then, unfortunately, pay the price.”

The smaller size observed in juvenile and young adult muskoxen is associated with poorer health and fitness, delayed puberty, and increased mortality, according to the research team.

In addition, a one-time extreme ice event that led to the death of dozens of muskoxen has been documented. In February 2011, an historically high tidal surge resulted in at least 52 muskoxen drowning at the northern coast of Bering Land Bridge peninsula.

Researchers also found historical records documenting deaths of whales — 170 Beluga and 150 narwhals — and sea otters due to rapid winter freezing and thawing at a range of single sites along the Aleutian Islands.

“Unlike polar bears, which are on the world’s stage, no one really knows about muskoxen, or cares,” said Berger. “They roamed with wooly mammoths but still survive. Muskoxen are feeling the heat, just as we humans are feeling the extremes of climate. These wild weather swings have massive impacts on us. Solutions are clear, but we fail to respond by changing our consumptive ways.”

Measuring a muskox, tracking temperatures

The research team analyzed head size of juvenile muskoxen using digital photo data over the span of seven years and at three sites in Alaska and Russia. They also compiled winter weather data for the Alaskan sites from the closest weather stations maintained by the National Oceanic and Atmospheric Administration. Data used to calculate rain-on-snow events on Wrangel Island, in the Arctic Ocean between the Chukchi Sea and East Siberian Sea, were from the Federal Hydro-meteorological Service of Russia, whose records date back to 1926.

color photo of Joel Berger and Fred Goodhope Jr., conducting research in Alaska
Biologist Joel Berger (left) confers with biotechnician Fred Goodhope, Jr. in Alaska.

Berger acknowledged the role his research plays “in a challenging political era.” His collaborators include Russian scientists in Asia and the Alaskan Arctic. Berger is not only a researcher, but he also serves as a diplomat of sorts, working closely with Russian research counterparts and the government. He praised them for their active engagement and willingness to share data.

“To better understand how species like the muskoxen are responding to a changing Arctic, we must collaborate, so that we can document rare and often tragic events, and gain additional insight from local people,” said Berger.

The study, “Climate degradation and extreme icing events constrain life in cold-adapted mammals,” was published in Scientific Reports, an online open access journal from the publishers of Nature.

Co-authors of the study include Cynthia Hartway, Wildlife Conservation Society and South Dakota State University; Alexander Gruzdev, Wrangel Island World Heritage Site; and Michael Johnson, U.S. Forest Service in Juneau, Alaska.

The Department of Fish, Wildlife and Conservation Biology is part of the Warner College of Natural Resources.