Arctocephalus philippii

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

• Biogeographic Regions
• neotropical neotropical
• pacific ocean pacific ocean

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.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• coastal coastal

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently

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.

• Mating System
• polygynous polygynous

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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.

• Parental Investment
• precocial precocial
• female parental care female parental care

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.

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.

• Key Behaviors
• natatorial natatorial
• motile motile
• territorial territorial
• social social
• dominance hierarchies dominance hierarchies

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.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Juan Fernandez Fur Seals are reported to feed on cephalopods, such as squid, and on fish.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • eats non-insect arthropods

• 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.

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.

• 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.

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.

Other Comments

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

Additional Links

Encyclopedia of Life

Contributors

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

References

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 .

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 .