Marine Mammals in Prince William Sound

Background

Three main groups of marine mammals are found in Prince William Sound: Whales and porpoises; seals and sea lions; and the sea otter. Brief highlights of their natural history are given below; for more detailed information, please see the "Further Reading" list below.

Whales and Porpoises (Cetaceans) Whales and porpoises belong to the animal Order Cetacea (from the Latin wordCetus, whale), and are the most aquatic of the Sound's marine mammals. The most common cetaceans found in Prince William Sound are killer whales, or Orcas, humpback whales, and Dall's and harbor porpoises. Other whales to look for are minke, pilot, and occasionally gray and fin whales.

Two forms of Orcas are found in the Sound. They are identical in appearance, and are the same species, but they differ markedly in their behavior and feeding habits. So-called "resident" Orcas occur mostly in the Sound, they eat fish exclusively, they vocalize often, and travel in large family groups or "pods." Resident Orcas also tend to be friendly toward boats.

"Transient" Orcas, in contrast, move in and out of the Sound from other areas, they eat marine mammals exclusively, they occur in smaller groups, and they are quieter than residents. Transients often cruise close to shorelines, looking for unwary harbor seals and sea otters. Whale biologists have catalogued over 300 individual Orcas in the Sound, based on the distinctive shape and markings on their dorsal fins and the "saddle" area directly behind the dorsal fin.

Humpback whales may occur from spring through fall anywhere in the deeper waterways of the Sound, although they are most common in the southwestern part. Whale biologists have identified and catalogued individual humpbacks in the Sound based on the unique black and white patterns on the underside of their flukes (tail fin).

Dall's and harbor porpoises are found throughout much of the Sound. Dall's usually travel in groups of up to 6 - 8, and they often approach moving boats to play in its wake. They can be identified at some distance by their characteristic crescent-shaped spray pattern when they surface, and once close to a boat, their black and white dorsal fin separates them from harbor porpoises. The latter are very shy, and are often solitary. Usually, the only thing one sees of a harbor porpoise is a brief glimpse of their dark back, bent in a wedge shape when they surface to blow.

Seals and Sea Lions (Pinnipeds)
Sea lions and seals are Pinnipeds, which means "fin-footed." Pinnipeds go ashore on rocky islets and headlands to breed and rest. Northern, or Steller's, sea lions and harbor seal are common in the Sound. Both species have been a long-term population decline in Alaska, and the sea lion was recently placed on the endangered species list. Sea lions do not breed in the Sound, but they do use several "haulouts," the largest being at The Needle. Sea lions are distinguished from seals by their small external ears and their ability to rotate their rear flippers forward. Harbor seals' ears are small holes on the sides of their head, and they cannot rotate their rear flippers.

Harbor seals are found throughout the Sound. They concentrate on icebergs near tidewater glaciers, which they use as floating haulouts, and at several island rookeries. Some females use icebergs for bearing young, but biologists do not yet know the relative importance of this habitat and land-based rookeries. The Sound's harbor seals are quite mobile, and move freely back and forth between glacier ice and their island haulouts. In spring of 1997, biologists counted 1,300 seals on the ice above the impassable (to boats) moraine reef in front of Columbia Glacier.

Increased boat traffic from sightseers near tidewater glaciers has conservationists keeping a watchful eye on their influence to harbor seals. Current studies of harbor seal/boat interactions by the National Park Service in Glacier Bay and Kenai Fjords will help conservationists assess the situation in Prince William Sound.

Sea Otters Sea otters are the largest members of the weasel family. They are found throughout Prince William Sound, with the largest concentrations in the southeastern sector. Near tidewater glaciers, they often haul out on small icebergs like harbor seals do. Breeding males tend to be solitary, while females and young of both sexes are more social, sometimes forming "rafts" of 100's of animals. Sea otters were nearly exterminated by fur hunters by the late 1800's, but their populations rebounded after protection in 1911. Their population in the Sound is currently healthy and growing.

​Marine Mammals in Prince William Sound

Background

Marine Mammals in Prince William Sound