Northern Fur Seal, photo by Marianne Aplin

 One of the special values of the Alaska Maritime Refuge is the concentrations of marine mammals that find sanctuary here to breed and raise their young.


The northern fur seal, endangered Steller sea lion, and harbor seals breed on the beaches and offshore rocky islets. Walrus come ashore to rest on refuge lands in the Bering and Chukchi seas. Sea otters use the nearshore waters around islands in the Aleutian Chain, Southeast Alaska, and off the Alaska Peninsula. When watching these amazing creatures, please observe these Marine Mammal Viewing Guidelines and Regulations.

Winter Visitors

Polar bears, year-round residents on St. Matthew Island until the end of the 1800s, sometimes travel on the winter pack ice to refuge lands in the Chukchi or northern Bering Sea.

Refuge Vital to Survival

The refuge is key to the life cycles and survival of many of these marine mammals, some of them threatened or endangered.


On the mainland areas of the refuge, the native mammals are similar to those of nearby areas. On islands, however, native land mammals are either absent or sometimes unique because they have been isolated in their development since the Ice Age.

None Unless Strong Swimmers

No native land mammals inhabit most of the Aleutian Islands. Some islands close to the mainland along the Alaska Peninsula and in Southeast Alaska can be reached occasionally by strong swimmers such as bears and river otters.

Some Unique

Several remote islands of the Bering Sea are a special case – once joined to the mainland during the Ice Age when sea levels were lower. Small mammals were left isolated on three of these islands when the sea rose, and now each has a unique species: St. Matthew - St. Matthew Island vole, Unalaska - Unalaska collared lemming, and St. Paul - Pribilof shrew.

Introduced Harm

Many islands have land mammals not native there. They were introduced accidentally or intentionally by humans – often devastating the native wildlife and plant life of their new homes. Learn more about the alien/introduced mammals and what the refuge has been doing to restore the natural biodiversity.

Learn more

Native Mammals - Distribution (pdf)

Marine Mammals of the Aleutian Islands (list includes abundance notes)

Sea Otter

Steller Sea LionLife History

Northern Fur SealLife History

Harbor SealLife History

Polar BearLife History

WalrusLife History