Arctocephalus philippiiJuan Fernandez fur seal

Geographic Range

Juan Fernandez fur seals are found today on the islands they were named for, off the coast of central Chile. It is suspected that they may also breed on the San Felix and San Ambrosio islands off northern Chile (Nowak, 1991)

Habitat

Juan Fernandez fur seals are usually found hauled out on rocks at the base of cliffs or ledges. They also have the tendency to use caves or recesses while on shore and have been seen 25 meters from a cave entrance. This habit may have saved them from hunters, as many of the caves are inaccessible to humans. Individuals are often seen active in the shallows, but adults generally forage in deep water. (Nowak, 1991)

Physical Description

The body is similar to that of most fur seals, slender and elongated, with males ranging from 150 to 200 cm, and females at about 140 cm in length. Weight of males is about 140 kg, and females weigh about 50 kg. All species of Arctocephalus have similar coloration. The under fur and bases of flippers are described as rich and chestnut brown in color. Males have a thick mane of long hair that is dark with white tips, giving the mane a frosted appearance. Males have a long pointed nose which is distinctive. Females have a noticeable grey-brown to dark brown coloration on the back but are paler below, especially on the chest and underside of the neck. ("Juan Fernandez Fur Seal", 1999; Nowak, 1991)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • Range mass
    50 to 140 kg
    110.13 to 308.37 lb
  • Range length
    140 to 200 cm
    55.12 to 78.74 in

Reproduction

The breeding behavior is very territorial, with males holding aquatic and land territories. Males will often fight to maintain these territories. Females within each territory mate with the resident male. A. philippii are polygynous in their mating system. (Ochoa-Acuna, et al., 1999; Francis and Boness, 1991)

Breeding in most fur seal and sea lion species occurs just after a female has given birth to a single pup from the preceding breeding season. In Juan Fernandez sea lions the peak pupping season is in late November and early December. Breeding occurs from November to January. Gestation is sligthtly less than one year. ("Juan Fernandez Fur Seal", 1999; Nowak, 1991; Seal Conservation Society , 2001)

  • Breeding interval
    Juan Fernandez Fur Seals breed once yearly.
  • Breeding season
    Mating occurs from November to December.
  • Average number of offspring
    1
  • Average gestation period
    12 months
  • Range weaning age
    7 to 10 months
  • Range time to independence
    7 to 10 months

Females give birth to a single pup and nurse on land. After a long initial post-natal suckling bout (averaging 11.3 days in length), females of A. philippii undergo long foraging trips (averaging 12.2 days in length), and this leads to some of the longest recorded intersuckling intervals for a mammal. Fat and energy content of milk is the highest of any member of the family Otariidae examined, allowing young to grow rapidly despite long periods of fasting. (Ochoa-Acuna, et al., 1999; Seal Conservation Society , 2001)

Lifespan/Longevity

The longevity of A. philippii is unknown but may be similar to A. gazella, in which expected life span is 13 years for males, with females typically living about 23 years. ("Juan Fernandez Fur Seal - Arctocephalus philippii", 2001)

Behavior

A. philippii are social animals living in large, male dominated groups. Males are highly territorial. These fur seals have the habit of resting in the water with heads down and hindflippers swaying out of the water, a behavior evident even in juveniles. Adults behaved aggressively towards a human diver on one expedition. Young A. philippii play almost constantly in shallow tide pools and are often seen lunging at each other's heads and foreflippers. ("Juan Fernandez Fur Seal", 1999; Nowak, 1991; Francis and Boness, 1991)

Communication and Perception

A. philippii are very vocal with calls ranging from a bark, usually when an animal moves or is playing, to a high-pitched scream often aimed at the approach of an intruder. Individuals may use a guttural cough if threatened. Females with pups will make a prolonged bawl. The communication is seemingly complex. Communication also occurs through visual and tactile cues and perhaps chemical cues, such as pheromones. (Nowak, 1991)

Food Habits

Juan Fernandez Fur Seals are reported to feed on cephalopods, such as squid, and on fish. ("Juan Fernandez Fur Seal - Arctocephalus philippii", 2001)

  • Animal Foods
  • fish
  • mollusks

Predation

Sharks and killer whales are known to attack other species of this genus although no specific information was available for A. philippii. They are fast and maneuverable swimmers and can seek refuge on land from these aquatic predators. (Shedden, 1999)

Ecosystem Roles

Although no exact interactions are known it can be assumed that A. philippii would effect the populations of their aquatic prey, and that any stillbirths would help local waterfowl.

Economic Importance for Humans: Positive

Juan Fernandez fur seals were used heavily by sealers in the late 1700s and early 1800s as a source of pelts, blubber, meat, and oil. Unfortunately this hunting lead to precipitous population declines and near extinction. ("Juan Fernandez Fur Seal", 2000)

  • Positive Impacts
  • body parts are source of valuable material
  • research and education

Economic Importance for Humans: Negative

There are no known adverse affects of Arctocephalus philippii on humans although the possibility of competition with commercial fisheries has been noted in conjunction with conservation efforts. ("Juan Fernandez Fur Seal - Arctocephalus philippii", 2001; "Juan Fernandez Fur Seal", 2000)

Conservation Status

During the late 17th century, A. philippii were abundant, with the population estimated as high as 4 million. After one century of heavy exploitation, they were believed to be extinct until 1965, when they were observed on Alejandro Selkirk Island. Since 1965 the population has increased dramatically, with the current population estimated at more than 12,000. Species of Arctocephalus are on Appendix 2 of CITES, and the IUCN classifies A. philippii as vulnerable. ("Juan Fernandez Fur Seal - Arctocephalus philippii", 2001; Nowak, 1991)

Other Comments

Due to the decline and subsequent rise in population size, A. philippii has been used in a number of genetic studies.

Contributors

Daniel Handysides (author), Andrews University, Tom Goodwin (editor), Andrews University.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

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.

acoustic

uses sound to communicate

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.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

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

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

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

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

UNEP World Conservation Monitoring Center. 2001. "Juan Fernandez Fur Seal - Arctocephalus philippii" (On-line ). Accessed December 9, 2002 at http://www.unep-wcmc.org/index.html?http://www.unep-wcmc.org/species/data/species_sheets/juanfern.htm~main.

International Marine Mammal Association. 1999. "Juan Fernandez Fur Seal" (On-line ). Accessed December 9, 2002 at http://www.imma.org/pinnipeds/juanfernandezfs.htm.

WWF - The Conservation Organization. 2000. "Juan Fernandez Fur Seal" (On-line ). Accessed Dec/12/02 at http://www.panda.org/resources/publications/species/underthreat/page19.htm.

Francis, J., D. Boness. 1991. The effect of thermoregulatory behavior on mating of A. philippii. Behaviour, 119: 104-126.

Nowak, R. 1991. Walker's mammals of the world. Baltimore: John Hopkins University Press.

Ochoa-Acuna, H., J. Francis, O. Oftedal. 1999. Influence of long intersuckling interval on composition of milk in the Juan Fernandez fur seal, A. philippii. Journal of Mammalogy, 80: 758-767.

Seal Conservation Society , 2001. "Juan Fernandez Fur Seal" (On-line ). Pinniped Species Information Pages. Accessed March 30, 2003 at http://www.pinnipeds.org/species/juanfur.htm.

Shedden, N. 1999. "South African and Australian Fur Seals" (On-line ). Accessed 12/12/02 at http://home.vicnet.net.au/~neils/africa/seal.htm.