Guadalupe Fur Seal (Arctocephalus townsendi)

The Guadalupe Fur Seal (Arctocephalus townsendi) exists on Guadalupe Island, 241 km off the coast of Baja California, Mexico. They are also found in the Gulf of California, and north to California state. This ‘bear headed’ seal was named after Dr. Townsend who made an expedition to the island in 1892, bringing home skulls that facilitated the first official documentation as a unique species. Their closest relative is the Juan Fernández Fur Seal, of which they were formally considered a subspecies, but they are now considered a bonafide species in their own right. Despite past decimation, they have recovered from the brink of extinction and seem to be steadily increasing. They are therefore at this time classified Least Concern. Estimated population size = 20,084.
A. townsendi are a large-bodied, sexually dimorphic fur seal (males up to 2.4 m long/ 220 kg, females up to 1.9 m/ 55 kg). Hind flippers are proportionately short, and fore flippers are long and fur-covered, with the exception of the tips. The males have heavy, rounded bodies with very thick necks and solid chests and manes. The crown of their head is convex and broad, and the muzzle is pointed with a flat top. Females too have dense fur on their neck and chest, though they are slighter in build than the males. Facially they have fairly pointed features with prominent snouts and long ear flaps. Vibrissae are characteristically short. Colouration in A. townsendi is typically dark grey-brown to charcoal grey, with females paler than males. Females may be buff or sandy underneath, while males often sport lighter grizzled flecks around their nape and crown.
Feeding behaviour:
Diet of A. townsendi seems to comprise chiefly of squid, of a variety of different species. Fish is thought to supplement this diet, and examples found in samples have included mackerel, tuna, sardine, hake, anchovy, smelt, sanddab, ridgehead, lanternfish and rockfish. They often forage at night, diving to shallow depths to take advantage of the available prey. Individuals may travel long distances (up to 4,000 km) during foraging trips.
Breeding behaviour:
Sexual maturity – males 4-5 years old/ females 4-5 years old.
A. townsendi are polygynous breeders, with territorial males vocalising and demonstrating their strength, in order to mate with up to 12 females. This occurs during June and July, and unusually, the species often dwells and breeds in caves during these hot summer months, perhaps for protection. Gestation duration is approximately 1 year, and pups are born with a jet black coat that already resembles the adult pelt, and browns over time. This first coat is moulted at around 3-4 months old. 1-2 weeks after the birth, the mother usually departs to the ocean for her first foraging trip and these trips can last many days, even up to a fortnight. However she will come back to nurse her young regularly until weaning at around 9 months of age. The adult moult is post-natal. Longevity for A. townsendi is around 20-23 years, though may be significantly lower for males (13-18).
A. townsendi does not have any subspecies.

Photo: Martin Stoffel

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