Northern Elephant Seals at Año Nuevo State Park

Elephant seals are true seals in the family Phocidae. Two living species are recognized: the northern elephant seal (Mirounga angustirostris) and the southern elephant seal (Mirounga leonina). Northern elephant seals display pronounced sexual dimorphism: adult males are substantially larger than females and develop an enlarged, inflatable proboscis used to amplify vocal threats during the breeding season.

Northern elephant seals spend approximately nine months of the year at sea, undertaking long foraging migrations across the North Pacific. At Año Nuevo, the main breeding season extends from December through March. Different age and sex classes return from spring through summer for their annual catastrophic molt, during which they shed their fur and an outer layer of skin. Juveniles also gather onshore during an autumn haul-out.

Like other true seals, northern elephant seals cannot rotate their hind flippers beneath their bodies. On land, they move through undulations of the trunk while using their foreflippers for support. In the water, propulsion comes primarily from lateral movements of the rear body and hind flippers.

The Año Nuevo Coast Natural Preserve within Año Nuevo State Park supports one of the world’s largest mainland breeding colonies of northern elephant seals. Commercial sealing reduced the species to a small surviving population in Mexico by the end of the nineteenth century, but its numbers subsequently recovered. Northern elephant seals are protected in the United States under the Marine Mammal Protection Act.