By Daniel Handysides
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)
Biogeographic Regions:
neotropical 
; 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. (Nowak, 1991)
These animals are found in the following types of habitat:
temperate ; saltwater or marine .
Aquatic Biomes:
coastal .
Physical Description
(110 to 308 lbs)
(55.12 to 78.74 in)
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. (International Marine Mammal Association, 1999; Nowak, 1991)
Some key physical features:
endothermic ; homoiothermic; bilateral symmetry .
Sexual dimorphism: male larger, sexes colored or patterned differently.
Reproduction
Juan Fernandez Fur Seals breed once yearly.
Mating occurs from November to December.
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. (Francis and Boness, 1991; Ochoa-Acuna, Francis, and Oftedal, 1999)
Mating systems:
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. (International Marine Mammal Association, 1999; Nowak, 1991; Seal Conservation Society, 2001)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; 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. (Ochoa-Acuna, Francis, and Oftedal, 1999; Seal Conservation Society, 2001)
Parental investment:
precocial ; 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. (UNEP World Conservation Monitoring Center, 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. (Francis and Boness, 1991; International Marine Mammal Association, 1999; Nowak, 1991)
Key behaviors:
natatorial ; motile ; territorial ; social ; 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. (Nowak, 1991)
Food Habits
Juan Fernandez Fur Seals are reported to feed on cephalopods, such as squid, and on fish. (UNEP World Conservation Monitoring Center, 2001)
Animal Foods:
fish; mollusks.
Predation
- sharks (Chondrichthyes)
- killer whales (Orcinus orca)
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: 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. (UNEP World Conservation Monitoring Center, 2001; WWF - The Conservation Organization, 2000)
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. (WWF - The Conservation Organization, 2000)
Ways that people benefit from these animals:
body parts are source of valuable material; research and education.
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. (Nowak, 1991; UNEP World Conservation Monitoring Center, 2001)
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.
