Counting Pacific Walruses

The Pacific walrus lives in the shallow waters over the continental shelf in the Bering and Chukchi seas. Walruses breed in the Bering Sea in winter. In spring and summer, adult females, young walruses and some adult males follow the retreating sea ice north through the Bering Strait into the Chukchi Sea, while most adult males stay in the Bering Sea. Walruses feed on small animals on the sea floor, such as clams and marine worms, and rest on sea ice or land between feeding trips.

Pacific walruses are a vital subsistence resource for Alaska Native coastal communities, which also hunt them to carry on cultural traditions such as ivory carving. Knowing the population's size and trend helps keep the harvest sustainable, supports co-management decisions, and helps identify risks to walruses as the Arctic changes.

Pacific walrus range in the Bering and Chukchi seas. U.S. Geological Survey.

Research from 2013 to 2022

Walruses are hard to count because they are spread unevenly over a vast, remote area. Two studies by the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service described the population as it stood around 2015:

• Trend: a study completed in 2018 found the population was stable.
• Size: a study completed in 2022 used genetic mark-recapture on biopsy samples from 8,303 walruses, collected on research expeditions from 2013 to 2017. It estimated about 260,000 walruses, with a possible range of 170,000 to 370,000.

New estimates are needed to see how the population is responding to a changing Arctic and to update assessments of whether the harvest is sustainable.

Pacific walruses in the Chukchi Sea. Photo by Ted Swem, U.S. Fish and Wildlife Service, MMPA Permit 14573C.

A new method, 2023 to 2026

Close-kin mark-recapture uses genetic information to find related pairs, such as a parent and its offspring, and uses how often those pairs appear in a sample to estimate the population's size and trend. It needs roughly half as many samples as the 2013–2017 project, which means less disturbance to the walruses.

The USGS and the Fish and Wildlife Service began a new round of expeditions in 2023 to apply the method. Expeditions were completed in 2023, 2025 and 2026, and results are expected in 2028.

An adult female Pacific walrus and her one-year-old offspring in the Chukchi Sea. Photo by Aminda Everett, U.S. Geological Survey, MMPA Permit 33776D.

Sources

• U.S. Geological Survey, "Pacific walrus population research," Fact Sheet 2026–3017. https://pubs.usgs.gov/publication/fs20263017/full
• The fact sheet cites Fay (1982) on walrus movements, Sheffield and Grebmeier (2009) on diet, Taylor and others (2018) on population trend, Beatty and others (2022) on population size, and Jacobson and others (2026) on close-kin mark-recapture.