Arctocephalus galapagoensis Heller 1904

5.

Galapagos Fur Seal

Arctocephalus galapagoensis

French: Otarie des Galapagos / German: Galapagos-Seebar / Spanish: Lobo marino de las Galapagos

Other common names: Galapagos Islands Fur Seal

Taxonomy. Arctocephalus galapagoensis Heller, 1904,

“Wenman Island,” Galapagos Islands, Ecuador.

Formerly, A. galapagoensis was considered a subspecies of A. australis. Monotypic.

Distribution. Galapagos Is, where they occur on almost all the islands.

Descriptive notes. Total length 150-160 cm (males) and 110-130 cm (females); weight 60-68 kg (males) and up to 33 kg, average 27-3 kg (females). Neonates are 60-80 cm and 3-4 kg. Dental formula I 3/2, C 1/1, PC 6/5 (x 2) = 36. Galapagos Fur Seals are the smallest species of otariid, and the least sexually dimorphic. Mature males are 1-1-1-3 times the length and 2-2-3 times the weight of mature females. They appear small and relatively compact. Short, straight muzzle tapers to small nose. Vibrissae are pale in adults. Eyes are large, and ear pinnae are long and conspicuous. Although they do not have a mane, adult male Galapagos Fur Seals have thicker shoulders than females. Males do not develop noticeable sagittal crest, but crown of head is slightly round compared with more flattened crown of females. Flippers are short and have dark, sparse, short fur that extends beyond wrists and ankles onto dorsal surface offlippers that are otherwise covered in black leathery skin. Fur is dark brown with gray to ruddy grizzling. In both sexes, muzzle is mostly buff-colored, and adult males can appear to be wearing pale mask. Adult females have pale grayishbuffy chest, and belly is buff to ruddy brown. Young are blackish, occasionally with pale fur around mouth and nose.

Habitat. Significant time hauled out on shore and favor rocky coasts with boulders and ledges for shelter from the sun. Because many Galapagos Fur Seals bear scars from shark bites, predators include sharks, as well as Killer Whales (Orcinus orca). Feral dogs are the only important terrestrial predators.

Food and Feeding. There is little specific information for this species, but they seem to prey on multiple species of squid and fish such as lanternfish (Myctophidae) and deep-sea smelt (Bathylagidae).

Breeding. There is no specific information for this species, but the Galapagos Fur Seal no doubt has the same general polygynous breeding system as described for the Northern Fur Seal (Callorhinus ursinus).

Activity patterns. Galapagos Fur Seals spend much time ashore, when not foraging or traveling. While at sea, Galapagos Fur Seals groom, rest, and feed as described for the Antarctic Fur Seal. Rookeries of Galapagos Fur Seals are situated close to feeding areas, and average length of female trips is the shortest for any species of fur seals. Most foraging occurs at night, possibly in pursuit of vertically migrating species when they are near the surface. Average dive is to a depth of 26 m and lasts less than two minutes; maximum depth recorded was 115 m, and the longest dive lasted five minutes.

Movements, Home range and Social organization. Galapagos Fur Seals are non-migratory, spending much time hauled out. Movements at sea are poorly known outside the breeding season. Lactating females make short foraging trips, indicating they remain close to the Galapagos Islands. Most of the colonies are located in the western and northern parts of the Galapagos Archipelago, near offshore upwelling areas conducive to marine productivity. Galapagos Fur Seals are capable of traveling to the coast of mainland Ecuador, where they occasionally haul out. Foraging trips by lactating females last an average of 1-5 days in the cool months (May—-November) and four days in the warm months (December-April). Female Galapagos Fur Seals provide their offspring with ¢.300 suckling visits, each lasting 0-5-1-3 days, before young are weaned at 18-36 months old. Although most females give birth to one offspring per year, they successfully rear only one offspring every two years. Because most young are not weaned until after they are more than two years old, young are often born to a female already attending an older offspring. Many newborns in this situation starve, and larger siblings kill some of them. Female Galapagos Fur Seals may allow two offspring to nurse, but this seldom continues long enough for the younger one to gain sufficient strength to survive.

Status and Conservation. CITES Appendix II. Classified as Endangered on The IUCN Red List. Based on counts in 1988-1989, population estimate of Galapagos Fur Sealsis 10,000-15,000 individuals. Sealers in the 19™ century brought the Galapagos Fur Seal to the brink of extinction, but it has since recovered. In the 1930s, they received full protection by the Ecuadorian government. Feral dogs once destroyed rookeries on Isabela Island, but a canine control program led to eradication of the dogs. Entanglement in fishing gear is reported occasionally but is minimal because of the no-fishing zone surrounding the Galapagos National Park. Galapagos Fur Seals are still at risk because the population size is modest and all breeding is restricted to a small group islands. Historical reduction of the population led to a genetic bottleneck, reducing population variability of the Galapagos Fur Seals, leaving it potentially more susceptible to infectious diseases and environmental stressors associated with climate change El Nino weather events, which raise sea-surface temperatures and decrease marine food resources in the eastern Pacific Ocean, are known to increase mortality rates young Galapagos Fur Seals, causing severe population swings.

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Bibliography. Alava & Salazar (2006), Arnold & Trillmich (1985), Arnould (2009), Aurioles & Trillmich (2008 Berta & Churchill (2012), Bonner (1981), Dellinger & Trillmich (1999), Horning & Trillmich (1999), Jefferson et (2008), Limbergeret al. (1986), Reijnders et al. (1993), Rice (1998), Trillmich (1986a, 1987), Trillmich & Dellinger (1991), Trillmich & Kooyman (2001), Trillmich & Wolf (2008), Wickens & York (1997), Wolf et al. (2007).