Walruses are circumpolar, but they are concentrated in geographically separated areas, with little or no chance of interbreeding.
Pacific walruses inhabit the Bering, Chukchi, and Laptev Seas.
Atlantic walruses inhabit coastal areas of northeastern Canada and Greenland.
Most walruses live where the air temperature is about -15° to +5°C (5° - 41°F).
Walruses are generally found where the water is no more than 80 m (262 ft.) deep. They prefer a habitat with a gravelly bottom. Walruses spend about two-thirds of their lives in the water.
Walruses haul out to rest and bear their young.
Walruses are adapted to a habitat of sea ice and prefer snow-covered moving pack ice or ice floes to land. They haul out on small rocky islands when ice is not present.
Eskimos call a traditional walrus haul-out area an ooglit.
The walruses' migration follows the extent of the pack ice. Throughout the year, they occur primarily in or near the southern periphery of the pack ice.
Pacific walruses winter in the central and south Bering Sea and summer in the Chukchi Sea.
Migration of the Canadian population is less well known. They seem to remain in the same general vicinity all year.
Walruses migrate primarily by swimming, but they may also ride ice floes.
Some walruses migrate more than 3,000 km (1,863 miles) each year.
Pacific walrus adult females and young walruses are more migratory than adult males.
Pacific walrus calves are born on the northward migration to the Chukchi Sea.
Several thousand Pacific walrus bulls remain in the south Bering Sea during the summer. When the ice melts, these bulls haul out on islands.
Some researchers have suggested that the hormones that control sperm development may also inhibit migration in adult males.
Total world walrus population is about 250,000 animals.
The Pacific walrus population is currently unknown but was last estimated at more than 200,000 animals in 1990.
The Pacific walrus population has been hunted to depletion and allowed to recover several times.
After the latest population depletion, which began in the 1930s, Pacific walruses were given protection by Russia, the State of Alaska, and the U.S. federal government. This protection led to the eventual recovery of the Pacific walrus population. Walruses reoccupied areas where they had not been seen for several years.
By the early 1980s, walruses appeared leaner. They increased their consumption of alternate foods such as fishes. Natural mortality increased, and birth rates decreased. This evidence supports the theory that the Pacific walrus population may have approached the carrying capacity of its environment.
As the Pacific walrus population grew, annual subsistence catches by indigenous Arctic peoples ranged from about 3,000 to 16,000 walruses per year until about 1990, and then decreased to an average of 5,789 animals per year from 1996 to 2000. Some scientists predict that, without long-term management, natural and human-related mortality factors could rapidly reduce the population once more.
Currently the US Geological Survey (USGS) and the Russian Knipovich Polar Research Institute are jointly undertaking a walrus population study. Using infrared imaging they locate walrus groups hauled out on sea ice. High resolution digital photography allows researchers to estimate group numbers. They also use satellite telemetry to estimate the percentage of the population visible during counts.