Arctocephalus townsendi, Merriam, 1897
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publication ID |
https://doi.org/ 10.5281/zenodo.6604474 |
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DOI |
https://doi.org/10.5281/zenodo.6604492 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E58-564B-9C15-90218BF9F989 |
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treatment provided by |
Diego |
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scientific name |
Arctocephalus townsendi |
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Guadalupe Fur Seal
Arctocephalus townsendi View in CoL
French: Otarie de Guadalupe / German: Guadalupe-Seebar / Spanish: Lobo marino de Guadalupe
Other common names: Lower Californian Fur Seal
Taxonomy. Arctocephalus townsend: Merriam, 1897 ,
“Guadalupe Island, off Lower California...collected on the beach on west side of Guadalupe” (Mexico).
Cranial characteristics and DNA analysis indicate that A. townsend: is most closely related to A. philippii . It is estimated that A. townsendiand A. philippi diverged from a common ancestor ¢.300,000 years ago.
In 2012 A. Berta and M. Chrurchill considered them to be mere subspecies, but most marine mammalogists have not adopted this proposal. Monotypic.
Distribution. Mainly in Guadalupe I, off the W coast of C Baja California (Mexico), recently has expanded SE to San Benito Is near the Baja California coast, and N to Channel Is (San Miguel I) and other S California islands and to Farallon Is off N California, USA. Wandering individuals have reached as far N as Washington State and one individual to SC Alaska. View Figure
Descriptive notes. Total length 200 cm (males) and a maximum length of 140 cm with a mean of 120 cm (females); estimated weight 160-170 kg (males) and 40-50 kg (females). Newborns are ¢.50-60 cm and c.6 kg. Dental formula 13/2, C 1/1, PC 6/5 (x 2) = 36. Guadalupe Fur Seals are sexually dimorphic. Mature males are 1-5-2 times longer and 3-4 times heavier than mature females. Adult male canines are larger and thicker than female canines. Males have thick fur, with dense pale underfur. Pale vibrissae are of medium length, and ear pinnae are long and conspicuous. Shape of crown is somewhat round in males. Guard hairs on head are long, emphasizing rise of crown, giving forehead slight slope where it meets shorter muzzle hair. Long straight muzzle tapers to point. Nose (rhinarium) is bulbous toward tip, and nostrils point down. Longer, coarse guard hairs form mane that reaches from crown to neck and shoulders. Neck, chest, and shoulders are broad. In contrast, abdomenis slight, tapering to hindflippers. Adult females, subadults, and juveniles also have long tapering muzzles, but noses are smaller. 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. Adult males are blackish-gray. Mane can appear grizzled because guard hairs are frequently tipped with whitish or tan on head and neck. Adult females, subadults, and juveniles are deep brown to blackish-gray above and pale below, particularly on chest, which can be buff to cream. All individuals may have light tan to ruddy brown on muzzle and face. Neonates have a thick black coat that molts after several months.
Habitat. Pelagic areas several hundred kilometers away from rookeries. Breeding territories of Guadalupe Fur Seals provide shade and preferably near shorelines with easy access to tidal pools, if not open water. They breed in caves and under boulders on coasts of rugged Guadalupe Island. Small groups of Guadalupe Fur Seals will rest on surface waters of the continental shelf near southern Baja California. Killer Whales (Orcinus orca) and sharks are likely predators. One Guadalupe Fur Seal had a wound similar to those made by cookie-cutter sharks (Isustius brasiliensis).
Food and Feeding. Based on fecal analysis of Guadalupe Fur Seals on San Benitos Islands, the diet was predominately squid (95%). Stranded individuals have been found with squid, bony fish, and crustaceans in their stomachs.
Breeding. The Guadalupe Fur Seal has the same general polygynous breeding system as described for the Northern Fur Seal ( Callorhinus ursinus ). For Guadalupe Fur Seals, the season from birth to weaning lasts from mid-June to August; average date of births is 21 June. Males maintain territories for at least 31 days, and each territory includes an average of six females. After pregnant females return to the rookery and give birth, they enter estrus 5-10 days later. Females may leave for their first foraging trip right after copulating, or they may remain ashore for a few more days. There is little information about foraging and attendance patterns of Guadalupe Fur Seals. Lactating females enter the water each day, probably for thermoregulation, but most of their time is spent ashore nursing their young. Young are nursed for c.9-11 months, and some females with offspring may stay in the vicinity of Guadalupe Island until the following spring.
Activity patterns. Much of what is known of activities of Guadalupe Fur Seals comes from studies of their breeding behavior on shore. Based on a few observations made at sea, they are generally solitary when away from their rookeries and groom, rest, and feed as described for the Antarctic Fur Seal. When traveling rapidly, they have been observed to “porpoise,” leaping clear of the water.
Movements, Home range and Social organization. Distribution of the Guadalupe Fur Seal at sea is poorly known. Recently, a few individuals have been sighted at sea during summer off Southern California and northern Baja California. They have been sighted in the Gulf of California and as far south as Zihuatanejo, Mexico. One individual was found stranded far north in the Cook Inlet, Alaska. Records from a few satellitetracked, adult female Guadalupe Fur Seals indicate they are capable of traveling 700-4000 km during offshore feeding trips that average 444 km away from the rookery.
Status and Conservation. CITES Appendix I. Classified as Near Threatened on The IUCN Red List. The Guadalupe Fur Seal is listed as threatened on the US Endangered Species Act. Sealers in the 19" century brought Guadalupe Fur Sealsto the brink of extinction, and it was not until 1926 that they were observed again on Guadalupe Island. This rediscovery led to a second round of hunting, and the Guadalupe Fur Seal was finally thought to be extinct. In 1949, a Guadalupe Fur Seal was sighted on San Nicholas Island off southern California. A scientific expedition to Guadalupe Island in 1954 found survivors there. Protected since the 1950s, the Guadalupe Fur Seal has recovered from a mere 200-500 individuals to 15,000-17,000 individuals. Commercial sealers in the 19" century did not consider the Guadalupe Fur Seal to be separate species from Northern Fur Seal, so species-specific records were not kept, making it difficult to reconstruct the historical distribution of the Guadalupe Fur Seal, although remains found in archaeological sites north to Washington State provide insight. Although numbers of Guadalupe Fur Seal are increasing by as much as 13% /year,they are still at risk because the population is small and most births are concentrated on Guadalupe Island. Population reductions during the 19" and 20™ centuries led to a genetic bottleneck, leaving extant population potentially more susceptible to infectious diseases and environmental stressors associated with climate change. Distribution of the Guadalupe Fur Seal overlaps with the California Sea Lion ( Zalophus californianus ), which has suffered from viral epizootics. Because Guadalupe Fur Seals depend on their thick coats for insulation, they are especially vulnerable to oil spills. Guadalupe Island, and most of the other islands used by the Guadalupe Fur Seal,is close to oil tanker traffic and offshore oil wells in southern California. Conflicts with fisheries appear to be minimal, but small numbers of Guadalupe Fur Seals may be taken as bycatch in gill nets or entangled in discarded fishing gear.
Bibliography. Arnould (2009), Aurioles-Gamboa & Camacho-Rios (2007), Aurioles-Gamboa, Elorriaga-Ver plancken & Hernandez-Camacho (2010), Aurioles-Gamboa, Hernandez-Camacho & Rodriguez-Krebs (1999), Aurioles & Trillmich (2008d), Belcher & Lee (2002), Bonner (1981), Brunner (2004), Etnier (2002), Fleischer (1987), Jefferson et al. (2008), Maravilla-Chavez & Lowry (1999), Peterson et al. (1968), Reijnders et al. (1993), Repenning et al. (1971), Rice (1998), Stewart (1981), Stewart et al. (1987), Weberet al. (2004), Wickens & York (1997).
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