Northern Fur Seal, photo by Marianne Aplin

Marine Mammals
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 See below for links to more information about individual species.

Land Mammals
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.

Endemic Species - unique to the area
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.

Invasive Species
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.

Sea Otter


Polar Bear

Steller Sea LionLife History

Northern Fur SealLife History

Harbor SealLife History