Commander Islands - Natural History

Natural History

Due to the high productivity of the Bering Sea shelf and the Pacific slope and their remoteness from human influence, the Commander Islands are marked by a great abundance of marine animal life and a relative paucity of terrestrial organisms. Notably, significant numbers of northern fur seals (some 200,000 individuals) and Steller sea lions (approximately 5,000 individuals) summer there, both on reproductive rookeries and non-reproductive haul-outs. Sea otters, common seals, and larga seals are likewise abundant. Indeed, the sea otter population is stable and possibly increasing, even as their population is falling precipitously in the rest of the Aleutian islands.

The neighboring waters provide important feeding, wintering, and migrating habitat for many whale species, many of which are threatened or endangered. Among these are: sperm whales, orcas, several species of beaked whales and porpoises, humpbacks, and right whales.

The much less diverse terrestrial fauna includes two distinct, endemic subspecies of arctic fox, (Alopex lagopus semenovi and A. l. beringensis). Though relatively healthy now, these populations had been significantly depleted in the past due to the fur trade. Most other terrestrial species, including wild reindeer, American mink, and rats have all been introduced to the islands by man.

Over a million seabirds gather to nest on numerous large colonies along almost all the coastal cliffs. The most common are Northern Fulmar, Common, Brunnich's and Pigeon Guillemots, Horned and Tufted Puffins, cormorants, gulls, and kittiwakes including the extremely local Red-legged Kittiwake which nests in only a few other colonies in the world. Waterfowl and sandpipers are also abundant along the pre-lake depressions and river valleys of Bering Island, though largely absent from Medny Island. Migratory birds of note with critical nesting or feeding habitat on the islands include such species as Steller's Eider, Pacific Golden Plover, and Aleutian Tern. Raptors of note include the rare Steller's Sea Eagle and Gyrfalcon. In total, over 180 bird species have been registered on the Commander Islands.

The fish fauna in the mountainous, fast running streams in composed primarily of migratory salmonids, including Arctic char, Dolly Varden, black spotted trout, chinook, sockeye, coho and pink salmon.

Bering Island was the only known habitat of Steller's sea cows, an immense (over 4000 kg) sirenian similar to the manatee. The sea cow was hunted to extinction within 27 years of its discovery in 1741. The Spectacled Cormorant, a large essentially flightless bird in the cormorant family, was similarly driven to extinction by around 1850.

There is no true forest on the Commander Islands. The vegetation is dominated by lichens, mosses and different associations of marshy plants with low grass and dwarf trees. Very tall umbellifers are also common. There are no amphibians or reptiles.