Why these marine mammals were hunted to the brink for their luxurious double coats

Nature · Published 3 October 2026 Swipe more like this →

In short: Fur seals are not true seals, but members of the eared seal family. Named for the dense underfur that once made them a prime target for commercial hunters, these animals possess unique physical adaptations that allow them to thrive in both the open ocean and on rugged coastal terrain.

Fur seals belong to the Otariidae family, distinguishing them from true seals by their visible external ear flaps and their ability to rotate their hind flippers forward to walk on land. While they share a common ancestor with bears, they have evolved into highly specialized marine hunters. Their defining feature is a double-layered coat: a fine, insulating underfur trapped beneath coarse guard hairs, which keeps them warm in frigid waters. This luxurious pelt, however, made them the focus of intense commercial sealing throughout the 18th and 19th centuries, leading to severe population collapses.

The family includes nine species divided into two groups. The northern fur seal is the sole representative of the genus Callorhinus and inhabits the North Pacific, while the eight species of the genus Arctocephalus are found primarily across the Southern Hemisphere. These animals exhibit extreme sexual dimorphism; males are significantly larger than females, often possessing bulkier heads and chests. During the breeding season, these social creatures congregate in massive colonies on shore. Dominant males aggressively defend territories to secure harems of females, which can include up to 40 individuals.

Despite their recovery in some regions, fur seals face ongoing challenges. The northern fur seal population, which plummeted during the 19th century, rebounded to 1.3 million individuals following legal protections enacted in 1911. However, many southern species have not seen such a recovery. Today, they contend with threats including climate change, which alters prey distribution, and overfishing, which limits their access to essential food sources like krill and squid. Furthermore, entanglement in discarded fishing gear remains a persistent danger, as these materials can restrict their movement and ability to hunt effectively in the wild.

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