The smallest of the pinnipeds is the Galapagos fur seal. It has a short, pointed muzzle, a little, button-like nose and rather large eyes. The coat of the Galapagos fur seal varies from dark brown to dark gray, with longer light-tipped guard hairs that create a grizzled appearance. Males also have a mane with slightly longer hairs, that go from the top of their head to their shoulders. The muzzle and also the fur of the underside are paler, with females and adolescents having a rusty-tan belly and a pale grayish-tan chest. The flippers are blackish. The pups are blackish-brown, though sometimes they have whitish or grayish margins around the nose and mouth.
This species is native to the Galapagos Islands, and the main colonies inhabit the western islands, with Isla Isabela and Isla Fernandina being the most populated. A colony of these seals has recently been discovered on Isla Foca in northern Peru. When in the Pacific Ocean’s deep waters they trail the Humboldt Current. When ashore, the Galapagos fur seal prefers rocky areas where it can shelter from the sun between large boulders and under ledges.
Galapagos fur seals are nocturnal feeders and make foraging trips that usually last about 16 hours. Their average dive takes them down 10 to 30 meters. On land they live together in large groups, divided up by the males’ attempts to establish territories, which can be as large as 200 square meters. Within these territories, females are usually found in groups numbering 6 to 10. Galapagos fur seals live in a mainly tropical environment and are a non-migratory species. They spend up to 30% of their time on land and subsequently have many behaviors that avoid the heat of the sun, including lying in shade next to boulders, under lava ledges and in caves, and making trips to the sea.
These seals are polygynous, a single male mating with multiple females. The males will establish territories and defend their group of females. One male may mate with between 6 and 10 females that are located within his territory. Breeding occurs from August to November. Gestation lasts for about 12 months, with delayed implantation (when the embryo, rather than developing, is maintained in a dormant state, which lengthens the normal gestation period), and a single pup is born. The pups begin to make ventures into the ocean at the age of 6 months and start to find their own food at 12 months. However, the young seals continue to rely on their mother’s milk as a main form of nourishment until around 2 or 3 years old, when they are weaned and become independent. Females reach sexual maturity between 3 and 5 years of age, and males take slightly longer, from 7 to 10 years, to gain sexual maturity and become big enough to defend their territory.
El Nino (when the temperature of the surface water of the equatorial Pacific Ocean fluctuates, having a strong impact on the climate) greatly affects this species, as it causes the warming of the ocean and thus reduces marine productivity and food sources, which makes the mother seal neglect her pup and wean it too soon, which can mean that the pup starves. Galapagos fur seals also suffer from oil spills and other pollution of their habitat. They are further threatened by natural predators, particularly feral dogs on the islands where they live.
According to the IUCN Red List, the Galapagos fur seal total population size is estimated at about 10,000-15,000 individuals. Their numbers are decreasing today and this species is classified as Endangered (EN).