Seal

Seals at a glance

Need to know

• Seals belong to the group Pinnipedia, including true seals, fur seals, and walruses.
• Crabeater seals are the most numerous large mammals after humans.
• The Baikal seal is the only exclusively freshwater seal species in the world.
• Harbor seals can sleep underwater, surfacing unconsciously to breathe.
• Some seals, like the Weddell seal, can dive deeper than 600 meters and remain submerged for over an hour.
• Seals use their sensitive whiskers to track the movement of prey in dark or murky waters.

About the Seals

Seals are semi-aquatic marine mammals found in nearly all the world’s oceans as well as some freshwater lakes. As members of Pinnipedia, they are divided into true seals (Phocidae), eared seals (Otariidae, which include sea lions and fur seals), and the walrus (Odobenidae), though 'seal' typically refers to true seals. These adaptable animals have streamlined bodies, thick layers of blubber for insulation, and remarkable swimming capabilities.

Seals exhibit a wide array of behaviors and occupy diverse environments—from the icy pack ice of Antarctica to the temperate coasts of Europe and North America, and even the freshwater Lake Baikal. While the majority of seal populations are stable or increasing, some species like the Mediterranean monk seal and Hawaiian monk seal are critically endangered. Seals play a vital role in marine food webs, and their complex social behaviors, diverse vocalizations, and curious intelligence make them favorites among animal enthusiasts and scientists alike.

Physical characteristics

Size: 1.2–5 meters in length (species-dependent). Weight: 45 to over 3,000 kg (species-dependent). Lifespan: 20–30 years on average.

• Streamlined, torpedo-shaped bodies
• Thick layer of blubber under skin
• Short or absent external ears for most species
• Large, sensitive whiskers (vibrissae)
• Webbed flippers adapted for swimming

Notable species

• Harbor Seal (Phoca vitulina) — Least Concern. Coastal areas, estuaries, sandy or rocky beaches Regions: North Atlantic Ocean, North Pacific Ocean, Baltic Sea, Bering Sea, coastal waters of North America, coastal waters of Western Europe.
• Gray Seal (Halichoerus grypus) — Least Concern. Rocky and sandy shores, ice edges during winter Regions: North Atlantic Ocean, North Sea, Baltic Sea, coastal waters of Canada, coastal waters of United Kingdom, coastal waters of Scandinavia.
• Hawaiian Monk Seal (Neomonachus schauinslandi) — Endangered. Coral reefs, sandy beaches, volcanic atolls Regions: Central Pacific Ocean, Northwestern Hawaiian Islands, Main Hawaiian Islands.
• Weddell Seal (Leptonychotes weddellii) — Least Concern. Pack ice, fast ice, near Antarctic coast Regions: Southern Ocean, coastal waters of Antarctica, Ross Sea.
• Crabeater Seal (Lobodon carcinophaga) — Least Concern. Thick Antarctic pack ice Regions: Southern Ocean, Antarctic pack ice, Weddell Sea, Ross Sea.
• Baikal Seal (Nerpa) (Pusa sibirica) — Least Concern. Deep open water, ice caves, rocky lake shores Regions: Lake Baikal.

Habitat and range

Original range: Evolved in polar and temperate marine environments of the Northern Hemisphere, with species radiating into Southern Hemisphere and isolated lakes

Current distribution: Seals inhabit every major ocean (except the Indian Ocean for most species), polar ice edges, temperate and subarctic coastlines, and a few freshwater lakes

Preferred environments: Coastal waters, Open ocean, Pack and fast ice (polar regions), Estuaries and river mouths, Freshwater lakes (Baikal seal only)

Regions: North Atlantic Ocean, North Pacific Ocean, Bering Sea, Baltic Sea, North Sea, Southern Ocean, Ross Sea, coastal waters of North America, coastal waters of Europe, Antarctic pack ice, Lake Baikal

Where to see Seals

• Puget Sound, Washington (USA) — June-August. Look for harbor seals lounging on rocky outcrops and piers.
• Farne Islands, United Kingdom — April–October. Boat tours offer good chances to spot both harbor and gray seals.
• Ross Sea, Antarctica — November–February (Antarctic summer). Weddell and crabeater seals can be seen on ice floes near research stations.
• Lake Baikal, Russia — February–April (ice cover). Seal-watching tours visit Baikal seals basking on the lake ice.

Behavior and diet

Diet: Primarily fish, squid, crustaceans, and some invertebrates; a few species eat krill.

Social structure: Varies by species: some are solitary for most of the year, while others gather in breeding colonies called rookeries during the pupping season.

Communication: Seals use a variety of sounds: barks, grunts, growls, trills, and underwater songs (notably among Weddell seals). They also use body language and touch.

• Can sleep underwater and surface to breathe without waking.
• Use vibrissae (whiskers) to detect vibrations from prey in low-visibility water.
• Some migrate seasonally between feeding and breeding grounds.
• Weddell seals maintain breathing holes in Antarctic ice by gnawing with their teeth.

Interactions with other animals

• Shark (predator): Large sharks, such as great whites, prey on seals in temperate and cold waters.
• Orca (Killer Whale) (predator): Orcas hunt seals in polar and temperate oceans, using strategic group tactics.
• Krill (prey): Crabeater seals feed almost exclusively on Antarctic krill, filtering them with specialized teeth.
• Gull (competitive): Gulls may compete for fish scraps or prey on vulnerable seal pups on breeding beaches.

Conservation

IUCN Red List status: Varies by species: overall Least Concern, but some critically endangered (e.g., Hawaiian Monk Seal)

Threats

• Bycatch in commercial fisheries
• Habitat destruction and climate change (loss of sea ice)
• Pollution and contamination (heavy metals, plastics)
• Illegal hunting and poaching
• Disturbance from tourism and boat traffic
• Disease outbreaks

Conservation efforts

• Marine mammal protection legislation (e.g. US Marine Mammal Protection Act)
• Habitat restoration and protected marine reserves
• International monitoring of population and health data
• Entanglement reduction and sustainable fisheries initiatives
• Public education campaigns

How to help

• Support marine protected areas and responsible eco-tourism.
• Reduce plastic and chemical pollution entering waterways.
• Report entangled or stranded seals to local wildlife agencies.
• Support conservation organizations working on seal research and rehabilitation.
• Practice responsible fishing and support sustainable seafood.

Seals facts for kids

Seals are playful, whiskery marine mammals that live on coasts, ice, and even in a big lake! They swim fast and catch fish using their flippers and sensitive whiskers. Some seals can even sleep underwater and hold their breath for a very long time.

• Some seal pups are born with fluffy white fur, called 'lanugo.'
• Seals wiggle on land but are super fast swimmers in water.
• Crabeater seals eat tiny shrimp called krill—not crabs!
• Harbor seals can sleep underwater without thinking about it.
• Seals can clap their flippers or make loud noises to talk to each other.

Did you know? The Baikal seal is the only seal in the world that lives only in fresh water—and it's found in Lake Baikal in Russia!

Watch & learn

• Secrets of Seal Communication and Behavior — BBC Earth. This documentary explores the social lives and vocalizations of true seals (Phocidae), providing rare underwater footage and expert commentary on their fascinating behaviors.
• Hunting and Survival of the Leopard Seal in Antarctica — National Geographic. National Geographic dives deep into the life of the leopard seal (Hydrurga leptonyx), showcasing its predatory adaptations and unique role in the Antarctic ecosystem.
• Life of Harbor Seals: From Pups to Adults — Smithsonian Channel. Detailed documentary telling the story of harbor seals’ birth, growth, and challenges in coastal habitats, with stunning close-ups and expert analysis.
• Kingdom of Ice: Weddell Seals Underwater World — PBS Nature. PBS Nature features the Weddell seal, focusing on its extraordinary abilities to dive and thrive in the extreme Antarctic environment.
• Seal Rescue: Real-Life Stories of Pinniped Rehabilitation — BBC Earth. Follow wildlife rescue teams as they rehabilitate injured or orphaned seals, showing both the challenges and successes in returning Phocidae family members to the wild.