Walruses are one of the largest pinnipeds and the only one that bears tusks (Fay 1981, Lydersen 2018, Keighley et al. 2021). The tusks can grow to be in excess of a meter long and can weigh 5 kg in large bulls; females have thinner tusks than males. Males can reach 3.6 m in length and weigh up to 1,500 kg, while females are somewhat smaller, reaching lengths of about 3 m and weighing up to 1,000 kg. Newborns are 1-1.4 m long and weigh 33-85 kg. Males have specialized integumentary nodes on their neck and shoulders that probably function as a signal of maturity, and they might also have a shield function during aggressive encounters (Miller and Kochnev 2021). Although some females can ovulate at four years of age, the majority do not give birth until they are 7-8 years old and usually produce one calf two- four years (Fay 1982, Chivers 1999, Taylor et al. 2018, Larsen Tempel and Atkinson 2020). Gestation lasts 15 months, including a period of delayed implantation that lasts 3–3.5 months. Calves are born in May. The period of calf dependency is long, they are often attended by their mothers for 2+ yrs (Kovacs and Lavigne 1992, Noren et al. 2014). Males become sexually mature between 7–10 years of age, but are not physically and socially mature enough to successfully compete for breeding opportunities until they are approximately 15 years old. Longevity is approximately 40 years (Fay 1981).

Walruses are extremely social animals, and when hauled out on land or ice they are normally found in tight groups ranging in size from a few individuals up to hundreds or even thousands. Pacific walruses tend to form larger herds of thousands or tens of thousands (Fay 1982, Monson et al. 2013, Bengtsson et al. 2021, Fischbach et al. 2022, Altukhov et al. 2024). Walruses seek extensive body contact with conspecifics, which might serve to conserve heat, and likely also facilitates group defense. When swimming at sea they are also usually found in groups, and mothers and calves maintain close physical contact in the water (as well as when on shore). Walruses are able to nurse their pups at sea, holding the pup upside-down against the mother’s body (Miller and Boness 1982); being adapted to suction feeding undoubtedly plays a role in this unique behaviour. There is significant sexual segregation outside the breeding season within both subspecies, with males often being found in areas distant from females and their calves. Pacific walrus females, until recently, remained on the sea ice even in summer, but declining ice conditions have resulted in them now coming to shore where very large haulouts have become the norm (Jay et al. 2012, MacCracken 2012, USFWS 2017). Courtship and mating occur during the winter (Fay 1982, Lowther et al. 2015) in areas with leads or in polynyas (Fay 1982, Fay et al. 1984, Jay and Hills 2005, Freitas et al. 2009, Speckman et al. 2011). Walruses are believed to be polygynous, with males forming a type of lek and displaying vigorously, while vocalizing, adjacent to females hauled-out on ice floes (Sjare and Stirling 1996, Sjare et al. 2003). Males produce bell-like sounds underwater using a pair of elastic pharyngeal pouches in the neck that can be inflated with air to serve as resonance chambers that make this unique sound; these pouches also allow males to float at the surface while resting at sea. There is intense male-male competition during mating and the tusks are used in these encounters. The tusks are also used during interspecific aggression against potential predators such as polar bears and killer whales (Miller and Kochnev 2021). Walruses also use their tusks to help get up onto ice floes. Walrus societies are complex, which is facilitated in part by a rich vocal repertoire (Miller and Kochnev 2021). Walruses will defend members of the group against predator attacks, even though the composition of walrus haul-out groups is quite fluid (Stirling 1984, KMK pers. obs.).

Walruses have quite a narrow ecological niche (Kovacs et al. 2016). They depend on 1) continental shelf waters with suitable bottom substrate to support a productive benthic community and 2) the presence of reliable open water areas where there is food close enough to land or sea ice for haulout (Lydersen 2018). The preferred haul out platform of Walruses is sea ice in both the Atlantic and Pacific regions (Gilbert 1999, Jay et al. 2014, Beatty et al. 2016, Lydersen 2018). However, Walruses routinely use coastal haul out sites in the summer and autumn in areas where sea ice is not available (Garlich-Miller and Jay 2000, Lydersen et al. 2008, Kovacs et al. 2014, Hamilton et al. 2015). Walruses are primarily benthic feeders, with most of their diving being shallow (to ‹50 m), although maximum dive records go to 462 m (Jay et al. 2001, Lowther et al. 2015, Garde et al. 2018). They use their stiff but bendable whiskers, which are highly innervated and sensitive (Kastelein and van Gaalen 1988) to search for prey in soft substrates (Marshall and Pyenson 2019). They also use their muzzles and their fore-flippers to clear access to prey and theyjet water to clear away sediments (Leverman et al. 2003). A wide variety of benthic invertebrates are consumed by Walruses, though a few species of clams make up the majority of the Walrus’s diet (Fay 1982, Sheffield and Grebmeier 2009, Skoglund et al. 2010, Beatty et al. 2016, Sonsthagen et al. 2020). But many species of worms, snails, soft shell crabs, amphipods, shrimp, sea cucumbers, tunicates, and slow-moving fish can fall prey to Walruses. Some individuals also prey on seals and seabirds (Lowry and Fay 1984, Seymour et al. 2014, Giljov et al. 2017). Foraging trips at sea last several days in Svalbard (Lydersen et al. 2008, Hamilton et al. 2015), but shorter periods appear to be the norm for the Pacific subspecies (Udevitz et al. 2009, Fischbach and Jay 2016). Elemental analysis of enamel in the teeth of Pacific Walruses suggests that animals in different areas eat quite different things and fall into at least two feeding “stocks” (Jay et al. 2008).
Haul-out patterns follow both diel and strongly seasonal patterns (Hamilton et al. 2015): the latter is in part be related to sea ice concentrations (Jay et al. 2017). During the winter Walruses spend 10–15 % of their time hauled-out, usually on ice in the Barents Region (Hamilton et al. 2015). This increases to peaks during terrestrial haul-out period in the summer months of 30% in Svalbard (Hamilton et al. 2015). Much of the year, males haul out for a day at a time and then spend several days at sea (Lydersen et al. 2008). Diving patterns change markedly during the winter mating period (Jan-Feb), when males dive to the bottom rarely, spending much of their time doing shallow dives, near ice edges (Lowther et al. 2015). On average Walruses in Svalbard are in the water 75% of the time in late summer, similar to other North Atlantic areas (Lydersen et al. 2008 and references therein). Estimates of “availability” to survey counts in the Pacific suggest similar strong seasonal differences, with 15% of animals hauled out in spring when surveys of animals on ice took place (Speckman et al. 2011) and 57% of animals haulout in late summer when they use shore-based sites (Fischbach et al. 2022, also see Battaile et al. 2017). After breeding in traditional areas, male walruses disperse broadly in the Pacific, covering the whole of the species range (Jay et al. 2012). Multi-year records for individual male Walruses in Svalbard show that individuals follow very set, but quite independent, migratory patterns between breeding and summer haul-out areas, showing very high site fidelity among years (Mikkelsen et al. 2024). 

Walruses are thought to be important benthic community “controllers”—sometimes referred to as ecological engineers—though the bioturbation they perform when foraging (Oliver et al. 1983, Ray et al. 2006). 

The primary natural predators of Walrus are Polar Bears and Killer Whales (Killian and Stirling 1978, Fay 1981).

Walruses have a discontinuous circumpolar Arctic and sub-Arctic distribution. They are primarily found in relatively shallow continental shelf areas (Rice 1998, Lydersen 2018). The Pacific subspecies ranges from the Bering and Chukchi Seas to the Laptev Sea in the west, bordering on the Beaufort Sea in the east, with vagrants recorded south into the North Pacific Ocean to south-central Alaska and Japan (Fay 1981, 1982). The Atlantic subspecies occurs from the eastern Canadian Arctic, across the Northeast Atlantic to the Pechora Sea and into the western parts of the Kara Sea (Stewart et al. 2014, Keighley et al. 2021). In the North Atlantic, Walruses have been recorded north to the North Pole (Lydersen et al. 2022), and routinely reside in areas that can have > 90% ice cover during winter (Freitas et al. 2009). The Atlantic subspecies has been extirpated from many areas of its historical range by excessive hunting (i.e., Gulf of St Lawrence (McLeod et al. 2014), in Iceland (Keighley et al. 2019), much of the coastline of West Greenland (Garde and Hansen 2021), and areas just north of Scoresby Sound in East Greenland (Born et al. 1997)). Vagrant Walruses have been reported from 13 countries in Europe, reaching south to the Bay of Biscay in France/Spain (Chiacchio and Aae 2024). They are rare, but do also occur on occasion, in the White Sea in Russia (https://tass.com/science/1032349).

Commercial hunting of Walruses is forbidden world-wide, but most populations are subject to subsistence harvests by indigenous people. Sustainable harvests are thought to have been recently achieved in Greenland following implementation of quotas in 2006 (Wiig et al. 2014, NAMMCO 2018). Hunting at terrestrial haul-outs is banned in Greenland and adult females are not supposed to be taken, though this issue is not yet completely solved. Harvests in the Pacific and in Canada are small compared to population sizes. In Canada Walruses are listed as a Species of Special Concern, largely because of the threat posed by climate change (COSEWIC 2021).

Walruses are in the Russian Red Book, and they are classified as VU (Vulnerable) on the Norwegian Red List because of overharvesting in the past and the threat posed by habitat losses due to climate change. In the Barents Sea Region Walruses are completely protected from harvesting in both Russian and Norway (Boltunov et al. 2010, Eldegard et al. 2021). Many protected areas in Svalbard are relevant for Walrus conservation (Kovacs and Lydersen 2006).

Pacific Walruses became federally protected from commercial harvesting in 1941 in the U.S. and they became further protected under the Marine Mammal Protection Act in 1972. The U.S. Fish and Wildlife Service monitors hunts, which are managed by subsistence walrus-hunting communities in Alaska. Annual quotas are set for Pacific Walrus harvests by local communities in the Russia Arctic (Kryukova 2019).

Transportation of walrus products has been regulated by CITIES import and export controls since 1975.