Seal

True seals vs. eared seals

“Seal” in common usage covers two distinct families:

• True seals (Phocidae) — no external ear flaps. Use back flippers for swimming, drag forward on land. Species: harbor, gray, harp, ringed, bearded, leopard seal, monk seal, elephant seal.
• Eared seals (Otariidae) — visible external ear flaps. Use front flippers for swimming, can rotate hind flippers forward to walk on land. Species: sea lions, fur seals.

The two groups diverged about 20 million years ago and have different body plans and behaviors. Most “seal” performance shows feature eared seals (sea lions) — they’re more agile on land.

Underwater hunters

Harbor seals are coastal foragers, eating mostly fish and cephalopods. They hunt by:

• Vibrissae (whiskers) — extraordinarily sensitive, able to track fish wakes through dark turbid water.
• Vision — adapted to low light, less effective in air.
• Hearing — excellent both in air and underwater.

A single seal can dive for 10–20 minutes and reach 200+ m depth. Their oxygen-storage adaptations include high blood volume, oxygen-rich myoglobin, and the ability to bradycardia (slow the heart) during dives.

Pup mortality

Seal pups face high mortality in their first year — predation by orcas, polar bears, and large sharks; competition for food when transitioning from milk to solid prey; entanglement in fishing gear.

The white-coated harp seal pups are particularly vulnerable; their fluffy white fur attracted commercial hunters for centuries before international protections.

A vocal life

Harbor seals are surprisingly vocal — both above and below water. They produce growls, snarls, clicks, and complex underwater “songs” used in courtship and territorial display. Different populations have measurable regional dialects.

Bearded seals (Arctic) produce some of the most complex underwater songs in any mammal — long, descending whistles audible for kilometers.