Arctocephalus philippii
Creators: name: Russell A. Mittermeier
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Carnivora
Otariidae
Arctocephalus
Arctocephalus philippii

description: 3.
Juan Fernandez Fur Seal
Arctocephalus philippii
French: Otarie de Juan-Fernandez / German: Juan-Fernandez-Seebar / Spanish: Lobo marino de Juan Fernandez
Taxonomy. Otaria philippii Peters, 1866,
“Insel Juan Fernandez.” Restricted by V. B. Scheffer in 1958 to “Isla Mas a Tierra, Islas Juan Fernandez, Chile.”
It is estimated that A. philippii and A. townsend: diverged from a common ancestor ¢.300,000 years ago. In a recent review in 2012, A. Berta and M. Chrurchill lumped both taxa in a single species with two subspecies, but most marine mammalogists have not adopted this proposal.
Monotypic.
Distribution. S Pacific, in Juan Fernandez Is and San Félix I (Desventuradas Is), which lie 600 km to the N.
Descriptive notes. Total length 200 cm (males) and 120-140 cm (females); weight mean 140 kg (males) and c.48 kg (females). Newborns are ¢.65—68 cm and 6.2-6.9 kg. Dental formula I 3/2, C 1/1, PC 6/5 (x 2) = 36. Juan Fernandez Fur Seals are sexually dimorphic. Mature males are c.1-4 times the length and c.3 times the weight of mature females. Pale vibrissae are of medium length, and ear pinnae are long and conspicuous. Shape of crown and forehead on males is fairly round. Muzzle is straight and long, tapering to fleshy nose (rhinarium) that is large and slightly bulbous toward tip. Mane of longer fur reaches from shoulders to head, where long guard hairs emphasize crown and forehead. Neck, chest, and shoulders are broad. Adult females, subadults, and juveniles also have long tapering muzzles, but their noses are smaller, giving muzzles more pointed appearance. Flippers have dark, sparse, short fur that extends beyond wrists and ankles onto dorsal surface of flippers that are otherwise covered in black leathery skin. Juan Fernandez Fur Seals have thick coats that sport dense underfur. Adult males are dark gray-brown to blackish-gray. Mane may appear as grizzled cape due to guard hairs on sides and neck, tipped in cream-to-auburn color. Adult females, subadults, and juveniles are dark brown to blackish-gray above and buff or cream-colored below. All Juan Fernandez Fur Seals may be light tan to ruddy brown on muzzle and face. Neonates have thick black coat.
Habitat. Away from coastal island waters into deep oceanic areas. Favored terrestrial habitats to haul out and for breeding are rugged volcanic shorelines, cliffs, and boulders. Suspected predators include Killer Whales (Orcinus orca), blue sharks (Prionace glauca), great white sharks (Carcharodon carcharias), and possibly Leopard Seals (Hydrurga leptonyx) that occasionally make it as far north as the Juan Fernandez Islands.
Food and Feeding. Juan Fernandez Fur Seals feed nocturnally on vertically migrating prey. Lanternfish (Myctophidae) and squid are the most important prey items. Their diet is not as diverse as other species of otariids, likely the result of low productivity in their offshore marine environment.
Breeding. The Juan Fernandez Fur Seal has the same general polygynous breeding system as described for the Northern Fur Seal (Callorhinus ursinus). For the Juan Fernandez Fur Seal, the breeding season extends from mid-November through January, and rookeries are abandoned by early September or October. Male Juan Fernandez Fur Seals defend small territories that average 36 m?and hold an average four females. Males may hold larger territories in shallow waters off the rookery. Lactating females leave on their first foraging trip c.11 days after giving birth. Although some trips may last only a single day, on average females stay away for 12-3 days, up to the maximum recorded 25 days, both being the longest for any otariid. Average length of time a female stays ashore to nurse her young is 5-3 days. Young are weaned in 7-10 months.
Activity patterns. While at sea, Juan Fernandez Fur Seals groom, rest, and feed as described for the Antarctic Fur Seal. Despite foraging in deep oceanic water, average dive depth of the Juan Fernandez Fur Seal is only 12-3 m, with an average duration of 51 seconds, suggesting surface feeding. Deeper dives can be made to 90-100 m, lasting c.6 minutes.
Movements, Home range and Social organization. Adult female Juan Fernandez Fur Seals travel long distances from breeding rookeries to reach their feeding areas. Average distance traveled is 653 km, which is the maximum for any species of otariids. Most foraging trips are made to the west and south-west of the Juan Fernandez Islands. Their distribution at sea is not well known, although they are generally restricted to the Juan Fernandez Archipelago. Individuals occasionally reach the coast of South America from Peru to Chile.
Status and Conservation. CITES Appendix II. Classified as Near Threatened on The IUCN Red List. Based on a 1990-1991 breeding census, total population of the Juan Fernandez Fur Seal 1s ¢.12,000 individuals. As with other southern fur seals, commercial hunting of the Juan Fernandez Fur Seal in the 19" century led to a population crash. It was thought to be extinct in the early 20" century but was rediscovered in the mid-20" century. With protection, the population has been slowly increasing ever since. Fisheries impacts are currently minimal, but the Juan Fernandez Fur Seal may face future challenges. Population reductions of the 19" century led to a genetic bottleneck, reducing genetic variability, which may increase vulnerability to disease or climate change. Climate change has the potential to affect marine environments of the South Pacific Ocean in ways that may negatively impact species already required to make extremely long distance and duration foraging trips during their breeding season.
Bibliography. Arnould (2009), Aurioles & Trillmich (2008c), Bonner (1981), Brunner (2004), Francis & Boness (1991), Francis et al. (1998), Hubbs & Norris (1971), Jefferson et al. (2008), Reijnders et al. (1993), Repenning etal. (1971), Rice (1998), Scheffer (1958), Torres (1987).
description: Published as part of Russell A. Mittermeier & Don E. Wilson, 2014, Otariidae, pp. 34-101 in Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona :Lynx Edicions on page 90, DOI: 10.5281/zenodo.6604474