FaunaHub

Seal

Marine MammalPinnipedCarnivore

Harbor seal (Phoca vitulina) hauled out on rocks in Puget Sound, Washington.

Harbor seal (Phoca vitulina) in Puget Sound.

Image: Mrkoww, CC BY 4.0, via Wikimedia Commons.

Overview

True seals are marine mammals of the family Phocidae, distinguished from sea lions and fur seals (family Otariidae) by the absence of external ear flaps and by hind flippers adapted for swimming but not for walking on land. The harbor seal (Phoca vitulina) is one of the most widely distributed and commonly cited reference species.

Habitat & Range

Seals occupy coastal and pelagic marine habitats across most of the world's oceans, with particularly diverse assemblages in cold and polar regions. Phocids haul out onto beaches, rocks, or pack ice to rest, moult, and breed. Specific range and habitat varies considerably between species.

Diet

Seals are carnivores, with diets dominated by fish, squid, and other marine prey. Leopard seals are a notable exception, taking penguins and other seals among their prey. Diet composition varies seasonally and by population.

Behavior

Most seals are excellent divers, with adaptations including collapsible lungs, oxygen-storing muscle, and bradycardia (slow heart rate) during dives. Many species are colonial at breeding haul-outs but otherwise foraging singly. Pups are typically nursed on very fat-rich milk and weaned over a relatively short period.

Human Interaction & Conservation

Several seal species were heavily exploited for fur, oil, and meat in the 19th and 20th centuries and remain conservation priorities — most notably the monk seals. Today threats include bycatch, plastic and chemical pollution, climate-driven sea-ice loss, and disturbance at haul-outs. In many regions, approaching seals on beaches is regulated or illegal because of welfare and disease-transmission risk. Always keep distance and report stranded or injured animals to local marine wildlife authorities.

Similar Animals

Sea lions and fur seals (Otariidae) have visible external ear flaps and hind flippers they can rotate forward to walk on land, unlike true seals. The walrus (Odobenus rosmarus) is in its own family but is closely related to the pinniped group.

Frequently Asked Questions — Seal

What is the difference between a seal and a sea lion?
True seals (Phocidae) lack external ear flaps and cannot rotate their hind flippers forward; on land they move with caterpillar-like undulations. Sea lions and fur seals (Otariidae) have small external ear flaps and can walk on land using all four flippers. Different family, different swimming mechanics.
Should I approach a seal on the beach?
No. In most regions it is illegal or actively discouraged to approach pinnipeds on beaches. Mothers may abandon pups if disturbed, and adult seals can bite and carry diseases. Report sick, injured, or stranded animals to local marine wildlife authorities.
How deep do seals dive?
Diving capability varies greatly by species. Some elephant seals dive routinely to depths over 1,000 m and for periods exceeding an hour. Smaller coastal seals dive much shallower. Authoritative species accounts give specific ranges.
Are seals endangered?
Conservation status varies sharply by species. The Mediterranean and Hawaiian monk seals are particularly threatened; many other species are listed as Least Concern. Verify the IUCN Red List for any species of interest.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.