The Pacific walrus is a subspecies of walrus (Odobenus rosmarus) found in the Bering, Chukchi, Laptev and East Siberian Seas. The reliance of walruses on sea ice for resting during the summer foraging period makes them particularly vulnerable to changes in climate and the associated loss of sea ice. As a result, the Pacific walrus is a candidate species for listing under the Endangered Species Act (ESA).
The first documented aerial survey of Pacific walruses was conducted jointly by the United States and the former Soviet Union in 1975, after the enactment of the Marine Mammal Protection Act (MMPA) in 1972. This survey provided an estimate of about 246,000 animals and subsequent surveys suggested a population decrease to about 201,000 by 1990. The most recent aerial survey, conducted in 2006 by the U.S. Fish and Wildlife Service (FWS), estimated the walrus population to be about 129,000 but with a large confidence interval of 55,000-550,000 animals. The 2006 survey did not cover the entire walrus range and therefore is likely to be an underestimate of the total population size. Although the estimates between 1975 and 2006 suggest that the population has declined, the differences in methods and geographic coverage between the surveys make it impossible to determine population trends over time. Surveying walruses is difficult because during the spring, when the surveys are conducted, walruses are distributed widely across the Bering Sea pack ice and spend a significant portion of their time in the water. Adverse weather conditions in this region further hinder survey efforts. Faced with these difficulties, FWS began testing new population estimation methods in 2012 and the effectiveness of these methods is currently being evaluated. Overall, walrus population growth rates tend to be slow, with mature females producing a calf on average every 3 years. However, natural mortality also tends to be low and walruses can be long-lived. Their only natural predators include polar bears, killer whales, and humans.
The Pacific walrus is being considered for listing under the Endangered Species Act (ESA). FWS was first petitioned in 2008 to list the walrus as threatened or endangered under the ESA and to designate critical habitat for the species. After a 12-month review of the best available science, FWS found that listing the walrus as threatened or endangered was warranted. However, the walrus remains a candidate species for listing as FWS must first consider other higher-priority species for listing. By court order, FWS must make a final decision on the listing of walrus by 2017. Walruses currently are afforded protection in the United States (other than subsistence hunting) under the MMPA and they are listed in Appendix III of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
What the Commission Is Doing
The Marine Mammal Commission maintains close contact with Alaska Native communities that rely on walruses as a source of subsistence. In February 2016, the Commission led a series of listening sessions in Alaska to learn more about the challenges that Alaska Natives are facing as a result of climate change. Participants in those sessions noted that walruses are becoming more difficult to find in places and at times of past abundance, and they are concerned about how the potential listing of walruses under the ESA would affect their harvesting activities.
Commission Reports and Publications
|Letter Date||Letter Description|
|July 7, 2016|
|October 30, 2015|
|July 17, 2013|
|February 8, 2013||
Application from the Alaska Oil and Gas Association for authorization to take polar bears and Pacific walruses incidental to oil and gas exploration activities in the Chukchi Sea and the adjacent western coast of Alaska
|June 20, 2012|
|January 3, 2011|
The greatest threat to the Pacific walrus is climate change. As the pack ice that they rely on during the summer foraging season in the Chukchi Sea diminishes, walruses are increasingly forced to seek refuge at land-based haul out sites. In the last few years, large aggregations of animals have been observed at haul out sites near Point Lay, Alaska. Such aggregations may be dangerous for calves and juveniles if disturbance by humans or other factors cause adults to stampede. Local communities have taken important measures, in collaboration with FWS, to limit the potential for such disturbance.
Increases in chemical contaminants and biotoxins are another threat to walruses. A 2016 study by Lefebvre et al. found that of the 13 Arctic marine mammal species tested, walruses had the highest concentrations of harmful algal bloom toxins. If harmful algal blooms increase in frequency and intensity, they could become a major concern not just for walruses but also for the Alaska Natives who depend on them for subsistence.
Disturbance from a variety of human activities in the Arctic, such as shipping and oil and gas development, can also have negative impacts on walruses. Marine traffic and noise associated with seismic surveys could interfere with the walrus migration or cause changes in behavior in the foraging grounds.
Although hunting of walruses for subsistence use could be considered a threat to the walrus population, current harvest levels are thought to be sustainable. Alaska Native hunters have expressed concern that walruses are sometimes difficult to hunt due to the lack of sea ice habitat. In 2015 a reduced availability of walruses to subsistence hunters led to a food security crisis in the Bering Strait region of Alaska.
The Future/Next Steps
FWS must make a decision by summer 2017 to either list the Pacific walrus as threatened or endangered under the ESA or to remove it from ESA consideration. If listed, critical habitat for walruses will then be proposed for designation. Unlike listing decisions, the designation of critical habitat must take into account potential economic as well as ecological impacts.