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Arctocephalus townsendi

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA OTARIIDAE

Scientific Name: Arctocephalus townsendi
Species Authority: Merriam, 1897
Common Name(s):
English Guadalupe Fur Seal
French Otarie de Guadalupe, Arctocéphale de Guadalupe
Spanish Lobo fino de Guadalupe, Oso Marino de Guadalupe
Taxonomic Notes: In 2011 the genus of all Fur Seals other than Arctocephalus pusillus was changed from Arctocephalus to Arctophoca, Peters 1866 (Committee on Taxonomy 2011) based on evidence presented in Berta and Churchill (2012). However, in 2013, based on genetic evidence presented in Nyakatura and Bininda-Emonds (2012), this change was considered to be premature and these species were returned to the genus Arctocephalus pending further research (Committee on Taxonomy 2013).

The species was originally named Arctocephalus townsendi (Merriam 1897) after a specimen collected on the beach on the west side of the type locality ‘‘Guadalupe Island, Baja California, México”. This species is also referred to as Arctophoca townsendi (Sivertsen 1954), Arctocephalus philippii (King 1954) and Arctocephalus philippii townsendi (Brunner 2004). Skull morphology and genetics suggest that the closest relative of A. townsendi is A philippii, which explains why the Guadalupe Fur Seal has been considered a subspecies of the latter. However, using criteria of skull morphology, Repenning et al. (1971) retained them as separate species, but their conclusion was based on a small sample size. Wynen et al. (2001) in a comparative study of two regions of the mitochondrial genome of the family Otariidae also separated these two taxa as species. A recent genetic study by Higdon et al. (2007) suggests that Arctocephalus townsendi and A. philippii are valid separate species with an estimated time of separation of about 0.3 mya.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2015
Date Assessed: 2014-10-10
Assessor(s): Aurioles-Gamboa, D.
Reviewer(s): Trillmich, F., Bohórquez-Herrera, J. & Hernández-Camacho, J.
Facilitator/Compiler(s): Lowry, L., Ahonen, H., Chiozza, F. & Battistoni, A.
Justification:
The range of Guadalupe Fur Seals was considerably reduced by exploitation. Previously, they occupied an area from the San Benito Archipelago to the islands in southern California. Past abundance estimates range from 100,000 to 200,000 animals. In the 1950s they numbered 200-500, but numbers have increased steadily to around 20,000 in 2010. The relatively small population, limited area of occupancy, and reduced genetic variability of this species, make them vulnerable to a variety of threats. However, they do not qualify for threatened listing under any IUCN criteria and are therefore listed as Least Concern.
History:
1996 Vulnerable

Geographic Range [top]

Range Description: The distribution of the Guadalupe Fur Seal is centred on Guadalupe Island (Fleischer 1987, Gallo-Reynoso 1994, Belcher and Lee 2002, Aurioles-Gamboa et al. 2010). A small breeding colony was discovered on the east side of the easternmost part of the San Benito Islands in 1997 (Maravilla and Lowry 1999); now animals are present and spreading on all three San Benito Islands (Aurioles-Gamboa et al. 2010, García-Capitanachi 2011, Esperón-Rodríguez and Gallo-Reynoso 2012). Since the 1980s, Guadalupe Fur Seals have been observed more frequently on San Miguel Island and other southern California islands including, the Farallon Islands off the coast of northern California (Bartholomew 1950, Stewart 1981, Stewart et al. 1987, Stewart et al. 1992, Hanni et al. 1997). Guadalupe Fur Seal vagrants have been sighted and recorded stranded in California, Oregon, and Washington, USA, particularly during El Niño years (Hanni et al. 1997, Etnier 2002). Since 2009, around 50 Guadalupe Fur Seals have been found on the beaches along the west coast of Magdalena Island, located around 25ºN, approximately 500 km south of the San Benito Islands (Aurioles, unpublished data). The species' distribution at sea is poorly known, but records from a few satellite-tracked adult females suggest they may travel several hundred kilometres during feeding trips (Gallo-Reynoso 1994). Guadalupe Fur Seals have been sighted regularly in the Gulf of California, Mexico (Aurioles-Gamboa et al. 1999) at the southern extent of their distribution.

Guadalupe Fur Seals were the most frequently encountered pinniped in archaeological deposits on the San Miguel Island prior to the seal exploitation period (Walker and Craig 1979). Indeed, its abundance in deposits dating from 3,500 years to the present, between 32°N and 50°N latitude, suggests that the highest density of sites and individuals occurred on the Channel Islands and southern parts of the mainland (34-36°N), with densities declining north of Point Conception (Rick et al. 2009).
Countries:
Native:
Mexico (Baja California, Baja California Sur, Guadalupe I.); United States (California, Oregon - Vagrant, Washington - Vagrant)
FAO Marine Fishing Areas:
Native:
Pacific – eastern central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Guadalupe Fur Seals were abundant prior to seal exploitation, when they were likely the most abundant pinniped species on the islands of southern California (Walker and Craig 1979). Sealers harvesting Fur Seals in California and Mexico did not distinguish between Northern and Guadalupe Fur Seals in their harvest records, which makes it difficult to reconstruct former populations and geographic ranges. However, at least 52,000 Guadalupe Fur Seals were killed on several islands off the Pacific coasts of Mexico and the United States from the late 1700s to 1848, and the last few were harvested in Mexican waters in the late 1800s (Townsend 1931).

The species has recovered from near extinction when only a few dozen animals remained. Recent censuses (2008-2010) indicate that the population on Guadalupe Island numbers approximately 17,581 individuals. Another 2,503 individuals were estimated at San Benito Islands during the same years (García-Capitanachi 2011), bringing the minimum population size to 20,084. The species' overall population is slowly increasing and spreading with minor, temporary, decreases associated with El Niño events. The population clearly continues to be only a small fraction of the population size reached prior to the seal exploitation period, which has been estimated at around 200,000 (Hubbs 1979). 

For most of the 20th century, the species only inhabited Guadalupe Island and showed a population growth of 13.7% annually from 1955 to 1993 (Gallo-Reynoso 1994). In 1949 an emaciated adult male was sighted at San Nicolas Island (Bartholomew 1950), followed by more frequent observations on other islands in southern California since 1969 (Seagars 1984, Stewart 1981, Stewart et al. 1987) including a territorial male and female with a pup at San Miguel Island (Melin and DeLong 1999). In 1997, a small group was discovered at the former rookery on the San Benito Islands, southwest of Guadalupe Island, near the Baja California coast. The numbers on the San Benito Islands for 2010-2011 have increased to around 3,000 individuals, but few pups are born there, indicating that this colony is mostly the result of immigration from the Guadalupe Island (Aurioles-Gamboa et al. 2010).

From 1991 to 1993, the breeding population on Guadalupe Island was composed of 35.7% adult females, 22.1% pups, 9.7% juveniles, 26.4% adult males, 4.7% sub-adult males and 1.3% undetermined individuals (Gallo-Reynoso 1994).  During the 2007 and 2008 breeding seasons, the San Benito Islands population structure was 23.4-34.5% adult females, 0.4% pups, 18.6-29.1% juveniles, 6.2-12.6% sub-adult males, 23.4-34.5% adult males and a large proportion of undetermined (33.3-39.2%) individuals (Aurioles-Gamboa et al. 2010).

Sexual maturity is attained by about 4-5 years of age and maximum longevity is approximately 20 years. Age-structure data are not available for the Guadalupe Fur Seal population, thus parameters like generation time are not reliable.
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: Guadalupe Fur Seals are sexually dimorphic, with territorial males being 3.8 to 4 times larger than adult females (Gallo-Reynoso and Figueroa-Carranza 1996). Fourteen adult females averaged 148.2 cm standard length (tip of nose to tip of tail) and their weight averaged 49.1 kg. Twelve territorial males averaged 219 cm (Gallo-Reynoso and Figueroa-Carranza 1996), and males averaging 180 cm weighed 160-170 kg (Bonner 1994).

Guadalupe Fur Seals are polygynous, with males establishing territories that are occupied by a small number of females (Peterson et al. 1968). Pups are born from mid-June to August with a median birth date of 21 June (Wickens and York 1997). From 1991 to 1993 the median peak pupping date was 3 July at Guadalupe Islands (Gallo-Reynoso 1994). For up to 31 days, males defend their territory with vocalizations, displays, and mutual displays with neighbouring bulls (Gallo-Reynoso 1994). Guadalupe Fur Seals prefer shores with abundant large rocks and lava blocks, often at the base of large cliffs.They inhabit caves and recesses, which provide protection and cooler temperatures, especially during the warm breeding season. This segregates them from other pinniped species (Peterson et al. 1968, Pierson 1987, García-Aguilar et al. 2013).

Oestrus occurs 5-10 days after a female gives birth, and females can leave for their first foraging trip right after mating, or stay at the colony for a few days before departing (Peterson et al. 1968, Pierson 1987, Gallo-Reynoso 1994). Foraging and attendance patterns are not well-known but the limited information from four instrumented adult females indicates they travel a total mean distance of 2,375 km. The average distance to the feeding grounds was 444 km and the duration of feeding trips averaged 14.4 days. Diving records for one animal showed a deepest dive of 82 m (Gallo-Reynoso et al. 2008).

Feeding habits are poorly known, particularly for the main colony on Guadalupe Island where the few scats samples analysed to date included remains of the cephalopods Onychoteutis banksi, Eucleoteuthis luminosa, and Dosidicus gigas, as well as several fish, including Scomber japonicus, Auxis thazard, and Sardinops sagax (Gallo-Reynoso 1994). A study conducted during 2000-2001 on the San Benito Islands examined 218 Guadalupe Fur Seal scat samples in which 95.6% of the prey were cephalopod beaks including mostly Loligo opalescens and in lesser abundance Gonatus sp. and Dosidicus gigas. The few fish remains (4.4%) identified were mostly from Merluccius productus, Engraulis mordax and Sardinops sagax (Aurioles-Gamboa and Camacho-Ríos 2007). A similar diet was described in another study conducted during the summer of 2007 (50 scats) and winter of 2008 (56 scats) with the squid Loligo opalescens and Gonatus sp., making up 74% of the summer diet. In winter, these two squid species, along with Dosidicus gigas composed 87% of the prey. The fish Argentina sialis, Merluccius productus, and Sebastes spp. complemented the Guadalupe Fur Seal diet in both seasons (Pablo-Rodríguez 2009). Esperón-Rodríguez and Gallo-Reynoso (2013) and Gallo-Reynoso and Esperón-Rodríguez (2013) also found Loligo opalescens as the main summer prey for juveniles and subadult males at San Benito Islands. 

Contents of faeces and gastrointestinal tracts from several individuals stranded off the coast of northern California near Farallon Island included Loligo opalescens, Gonatopsis sp., Onychoteuthis borealis japonica, as well as several fish species: Citharichthys sordidus, Lampanyctus sp., Protomyctophum sp., and Scopelogadus sp. (Hanni et al. 1997).

Killer Whales and Sharks, particularly Great White Sharks, are regularly seen around Guadalupe Island during the summer, and are most likely predators of Guadalupe Fur Seals. These two predators are rarely seen around the San Benito Islands.
Systems: Terrestrial; Marine

Use and Trade [top]

Use and Trade: Guadalupe Fur Seals were hunted to near to extinction by the late 19th century. There were no reports of the species until 1926, after which all animals that could be found were harvested for fur with the last reported kill in 1928. Although the species was declared extinct for a second time, scattered, unconfirmed reports during the 1930s raised suspicions that Guadalupe Fur Seals might have survived. In 1954 expedition to Guadalupe Island confirmed the species' survival (Hubbs 1956) and the Mexican government fully protected the species.

Threats [top]

Major Threat(s): Although the Guadalupe Fur Seal population is steadily growing, the species is still at risk because the total population remains relatively low and nearly all pup production occurs on only one island. Since the species passed through a genetic bottleneck and recovered from a very small number of individuals, genetic diversity was suspected to be low. Bernardi et al. (1998) tested both nuclear and mitochondrial DNA in a sample of 36 individuals finding high levels of genetic variability relative to other species that experienced similar bottlenecks. However, when pre-bottleneck material is compared to material from animals in the surviving population, a significant loss of genetic variability is evident (Weber et al. 2004).

The feeding grounds of the species include the region around Guadalupe Island and the San Benito Islands and the lower part of the California Current. This region is influenced by human population centres with contaminant runoff, extensive oil tanker traffic, and offshore oil extraction activity in southern California. Like all fur seals, Guadalupe Fur Seals are vulnerable to oil spills because of their dependence on their thick pelage for thermoregulation. 

El Niño events may cause negative effects on the Guadalupe Fur Seal population dynamics due to high pup mortality caused by storms and hurricanes (Gallo-Reynoso 1994). Most of the temperate Eastern Pacific pinnipeds are exposed in some degree to deleterious effects of the El Niño (Trillmich and Ono 1991, Gerber and Hilborn 2001). Guadalupe Fur Seals share most of their haul-out and breeding sites with California Sea Lions, which have suffered from viral disease outbreaks in the past, and could be a vector for the transmission of diseases from terrestrial sources to Guadalupe Fur Seals. Additionally, human populations on the Guadalupe and San Benito Islands have the potential to introduce exotic fauna and diseases.

No conflicts with commercial fisheries are apparent at present time, although gillnet and set-net fisheries probably take some animals, as is likely also the case for entanglement in marine debris. There is a possibility for negative interactions between Guadalupe Fur Seals and Lobster fishermen particularly if the Fur Seal population continues to increase.

Conservation Actions [top]

Conservation Actions: The Guadalupe Fur Seal and its habitat are protected by the Mexican government and tourist visits to breeding islands are regulated and very limited. In the United States, the species is protected by the Marine Mammal Protection Act and the Fish and Game Code of the State of California. The Guadalupe Fur Seal was listed as threatened under the U.S. Endangered Species Act in 1985, which automatically assigned the species the status of depleted under the Marine Mammal Protection Act.

Citation: Aurioles-Gamboa, D. 2015. Arctocephalus townsendi. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 01 September 2015.
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