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Arctocephalus townsendiGuadalupe fur seal

By Mark Nabong

Geographic Range

The northernmost border of the range of A. townsendi is the Channel Islands, CA. The southern range border is Cedros Island, Baja California, Mexico. The only current breeding area is on Guadalupe Island, 290 km west of Baja California. The Guadalupe fur seal is the rarest of the fur seals, and it is also the only species of Arctocephalus found in the Northern Hemisphere. They have also been sighted as far south as Puerto Gurrero, near the Mexico/Guatemala border, as far north as the Point Reyes National Seashore in California, and possibly in the Gulf of California. It is possible that the true range of the species is underestimated due to the rarity of sightings. (Aurioles-Gamboa and Hernandez-Camacho, April 1999; Seal Conservation Society, 2001)

Habitat

Guadalupe fur seals only live on rocky coasts and in the caves found along these shores. They can dive to an average maximum depth of 17m for an average of 2.5 minutes. (Seal Conservation Society, 2001; Whitaker, 1997)

  • Range elevation
    0 (high) m
    0.00 (high) ft
  • Range depth
    onshore to 17 m
    to 55.77 ft

Physical Description

The fur of Guadalupe fur seals is brownish gray dorsally, with a silvery and yellowish-gray "mane" on the nape of the neck. Their snouts are pointed, with a rust-orange color on the sides.

This species has great sexual dimorphism. Adult males usually weigh about 124 kg, and may get up to 160 kg, females weigh about 50 kg, rarely over 55. Males grow up to 1.9 m long, females to 1.4 m.

(Whitaker 1997; Wickens & York 1997)

  • Sexual Dimorphism
  • male larger
  • Range mass
    50 to 160 kg
    110.13 to 352.42 lb
  • Range length
    1.9 (high) m
    6.23 (high) ft

Reproduction

Guadalupe fur seals have a polygynous breeding system, which involves a male seal with a territory (a bull) defending both his terriory and the females in his harem. The harem numbers between 4 to 12 females, each of which typically have one pup that they nurse.

Male Guadalupe fur seals are territorial, like other fur seals. They defend harems that number an average of 6.2 breeding females for each territorial bull. Males will defend their territory for 35 to 122 days. Unlike most other seal species, the males of A. townsendi occasionally observe their harems from the water. Female Guadalupe fur seals mate 7-10 days after giving birth to a pup conceived the previous year (post-partum estrus). Females lactate for an average of 9-11 months; how this related to the actual length of time before weaning is unclear.

(Whitaker, 1997; Wickens & York, 1997)

  • Breeding season
    15 June - 22 July
  • Average number of offspring
    1
  • Average gestation period
    approximately 12 months
  • Average weaning age
    most likely 11 months

Behavior

Mother seals use olfactory clues to find their pups after foraging trips.

The seals are not migratory, but a male and his females will occasionally diperse to new areas.

(Whitaker 1997; Wickens & York 1997)

Communication and Perception

Food Habits

Guadalupe fur seals eat a variety of fish, including lantern fish, mackerel, and fish in the muctophid family. Squid also constitute a major part of their diet. In all cases, the seals swim out to sea and dive for their prey items. During the breeding season, females make 2 to 6 day forging trips to sea, coming onshore in between each trip in order to suckle their pups.

Anchovy otoliths (bony concretions formed in the ears of fish) have been found the the digestive tracts of Guadalupe fur seals, but they are believed to be remains left from feeding of the seals by fishermen.

(Hanni et al. 1997; Seal Conservation Society 2001; Whitaker, 1997)

  • Animal Foods
  • fish
  • mollusks

Ecosystem Roles

The Guadalupe fur seal plays the role of predator in the shoreline communities it inhabits.

(Whitaker 1997)

Economic Importance for Humans: Positive

Prehistorically, A. townsendi may have been hunted by Chumash Indians at San Miguel Island and other Channel Islands in California. The seal produces a rich, dense fur that was highly prized up until recent times, with the species nearly driven to extinction by seal hunters in the 1880's. In 1892, only seven individuals were known to exist. The population has rebounded, and the trade in the fur of Guadalupe fur seals is prohibited.

(Melin & DeLong 1999; Whitaker 1997)

Conservation Status

The Guadalupe fur seal was nearly hunted to extinction in the 1880's, with the known population numbering only 7 individuals in 1892. Other than two males sold to the San Diego Zoo in 1928, only one other GFS was sighted until 1954. Guadalupe Island was declared a seal sanctuary by the Mexican government in 1975. The Guadalupe fur seal was first placed on the "threatened" list in the US on March 11, 1967. By 1984 there were 1,600 seals in the Guadalupe Island population, including around 650 new pups. Current estimates place the population number at >7,000 individuals. Despite the bottlenecks of the late 1800's, there still remains a high level of genetic variability in the population. The population of Guadalupe fur seals is growing at the rate of 11.5% per annum.

(Bernardi et al. 1998; Seal Conservation Society, 2001; USFWS 2001; Whitaker 1997; Wickens & York 1997)

Contributors

Mark Nabong (author), University of Michigan-Ann Arbor, Kate Teeter (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

threatened

The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorized as Endangered (E), Vulnerable (V), Rare (R), Indeterminate (I), or Insufficiently Known (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorized as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

References

Aurioles-Gamboa, D., C. Hernandez-Camacho. April 1999. Notes on the southernmost records of the Guadalupe fur seal, *Arctocephalus townsendi*, in Mexico. Marine Mammal Science, 15(2): 581-583.

Bernardi, G., S. Fain, J. Gallo-Reynoso, A. Figueroa-Carranza, B. Le Beouf. 1998. Genetic variability in Guadalupe fur seals.. Journal of Heredity, 89(4): 301-305.

Hanni, K., D. Long, R. Jones, P. Pyle, L. Morgan. May 1997. Sightings and strandings of Guadalupe fur seals in Central and Northern California, 1988-1995.. Journal of Mammalogy, 78(2): 684-690.

Melin, S., R. DeLong. July 1999. Obervations of a Guadalupe fur seal (*Arctocephalus townsendi*) female and pup at San Miguel Island, California.. Marine Mammal Science, 15(3): 885-888.

Seal Conservation Society, 2001. "SCS: Guadalupe fur seal" (On-line). Accessed Tuesday, 20 November 2001 at http://www.pinnipeds.fsnet.co.uk/species/guadfur.htm.

US Fish & Wildlife Service, 11/20/2001. "Species List: Guadalupe fur seal profile" (On-line). Accessed Tuesday, 20 November 2001 at http://ecos.fws.gov/species_profile/species_profile.html?spcode=A0A8.

Whitaker, J. 1997. National Audubon Society Field Guide to North American Mammals. New York: Alfred A. Knopf.

Wickens, P., A. York. April 1997. Comparative population dynamics of fur seals. Marine Mammal Science, 13(2): 241-292.

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