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Overview

Brief Summary

Biology

These social animals live in large, male-dominated groups in which breeding behaviour is highly territorial. Males hold territories both on land and in the water, with females within each territory mating with the resident male. As such, males will often fight fiercely to maintain these territories (6). Breeding occurs from mid-November until the end of January, immediately after pupping, with most pups from the preceding breeding season being born from late November to early December (2). Thus, gestation takes a little under one year. Females give birth to a single pup each year, which they then nurse on land, for a period of about 8 to 12 months (7). Soon after the birth of the pup, the female will mate again, before departing to sea to feed, returning from time to time to suckle her pup. A female returning from a feeding trip comes to the beach where she left her pup, and calls for it with a characteristic call. The pup answers with its own call, which is recognised by the mother, and their identity is confirmed by smelling the pup (6). The diet includes at least five varieties of squid, and there are reports that these fur seals also feed on various fishes and lobster (2). Sharks and killer whales are known to prey on Juan Fernández fur seals (5).
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Description

Remarkably, the Juan Fernández fur seal was considered extinct until it was happily rediscovered in 1965, although it nevertheless remains rare (2). Like most fur seals, this species has an elongated, slender body and a long, pointed snout and flippers (2) (4). Adult males have a particularly long muzzle that may be slightly down-curved at the tip, and which ends in a large, bulbous, fleshy nose, creating a shark-like silhouette (2). Adult males also develop thicker and more muscular necks, surrounded by a mane of long, coarse, dark hair with silver tips, giving the mane a frosted appearance (2). The necks and fore-flippers of the males are usually scarred from fighting (5). The back and belly are dark, blackish-brown in males, while the crown down to the ears and nape to the shoulders sometimes appear silvery-grey, against a darker throat and neck. Adult females are grey-brown to dark brown above, and variably paler below, especially on the chest and underside of the neck, which can be creamy grey, and there may be areas of lighter colour on the face. Both sexes have whitish-cream whiskers (2).
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Distribution

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 ; pacific ocean

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

Breeding is restricted the Juan Fernández Archipelago, and the islands of San Felix and San Ambrosio, off the coast of Chile (6), and the seal can be found in an incompletely known area of surrounding waters (2).
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Physical Description

Morphology

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.

Range mass: 50 to 140 kg.

Range length: 140 to 200 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; sexes colored or patterned differently

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Ecology

Habitat

Depth range based on 5 specimens in 2 taxa.
Water temperature and chemistry ranges based on 5 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 13.108 - 16.503
  Nitrate (umol/L): 0.212 - 1.629
  Salinity (PPS): 32.817 - 33.451
  Oxygen (ml/l): 5.646 - 6.141
  Phosphate (umol/l): 0.364 - 0.626
  Silicate (umol/l): 2.206 - 4.946

Graphical representation

Temperature range (°C): 13.108 - 16.503

Nitrate (umol/L): 0.212 - 1.629

Salinity (PPS): 32.817 - 33.451

Oxygen (ml/l): 5.646 - 6.141

Phosphate (umol/l): 0.364 - 0.626

Silicate (umol/l): 2.206 - 4.946
 
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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 ; saltwater or marine

Aquatic Biomes: coastal

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Depth range based on 5 specimens in 2 taxa.
Water temperature and chemistry ranges based on 5 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 13.108 - 16.503
  Nitrate (umol/L): 0.212 - 1.629
  Salinity (PPS): 32.817 - 33.451
  Oxygen (ml/l): 5.646 - 6.141
  Phosphate (umol/l): 0.364 - 0.626
  Silicate (umol/l): 2.206 - 4.946

Graphical representation

Temperature range (°C): 13.108 - 16.503

Nitrate (umol/L): 0.212 - 1.629

Salinity (PPS): 32.817 - 33.451

Oxygen (ml/l): 5.646 - 6.141

Phosphate (umol/l): 0.364 - 0.626

Silicate (umol/l): 2.206 - 4.946
 
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When ashore, these fur seals are usually found on rocky and volcanic shorelines with boulders, cliffs, overhangs, and caves (2).
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Trophic Strategy

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

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods)

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Associations

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.

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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.

Known Predators:

  • sharks (Chondrichthyes)
  • killer whales (Orcinus orca)

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Known predators

Arctocephalus philippii is prey of:
Chondrichthyes
Orcinus orca

This list may not be complete but is based on published studies.
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Known prey organisms

Arctocephalus philippii preys on:
non-insect arthropods
Actinopterygii
Mollusca

This list may not be complete but is based on published studies.
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Life History and Behavior

Behavior

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 ; tactile ; acoustic ; chemical

Perception Channels: visual ; tactile ; acoustic ; chemical

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Life Expectancy

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.

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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

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.

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.

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.

Parental Investment: precocial ; female parental care

  • Francis, J., D. Boness. 1991. The effect of thermoregulatory behavior on mating of A. philippii. Behaviour, 119: 104-126.
  • International Marine Mammal Association. 1999. "Juan Fernandez Fur Seal" (On-line ). Accessed December 9, 2002 at http://www.imma.org/pinnipeds/juanfernandezfs.htm.
  • 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.
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Conservation

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.

CITES: appendix ii

IUCN Red List of Threatened Species: near threatened

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Status

Classified as Near Threatened (NT) on the IUCN Red List (1), and listed on Appendix II of CITES (3).
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Threats

Once abundant, this fur seal was heavily exploited by commercial sealers from the 17th to the 19th centuries for its pelt, blubber, meat and oil, and by the beginning of the 20th century it was believed to be extinct (5). When the species was rediscovered in 1966, just 200 individuals survived (2), but the population has since steadily increased (8). However, despite being protected by the Chilean government, the Juan Fernandez fur seal is sometimes poached illegally for lobster bait, fur and meat (4) (5). Occasional reports also exist of the seal becoming entangled in fishing nets and plastic waste (5). There is an additional concern that the seal may have to compete with fisheries for its food, and due to its limited size, the population is vulnerable and may suffer from a lack of genetic diversity (4) (5).
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Management

Conservation

After rediscovery, the species was given total protection by national Chilean legislation in 1978 (5). This measure appears to have been successful as, since then, there has been an annual population increase of 16 to 17 percent, in spite of occasional illegal hunting (4).
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Relevance to Humans and Ecosystems

Benefits

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.

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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

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Wikipedia

Juan Fernández fur seal

The Juan Fernández fur seal (Arctocephalus philippii) breeds on the Juan Fernández Islands off the coast of Chile, named after the islands they were found on.[2] It is the second-smallest of the otariid seal (the closely related Galápagos fur seal is smaller still). Discovered by navigator Juan Fernández in the 16th century, the seals became a target for sealers in the Maritime Fur Trade era. They were thought extinct in the mid-20th century until a population of 200 was found. The population was protected and has grown quickly. There are now believed to be at least 10,000 animals on and around the island.

Description[edit]

The seals have a relatively robust body and a long, slender and pointed snout. They have stubby foreflippers and hindflippers, and a mane of long, coarse guard hairs from the top of the head to the shoulders. Adult males are dark brown to black, but the guard hairs can have yellow or tan tips. The males also have a more bulbous nose than the females and juveniles, as well as being longer than the adult females. The adult females have an overall brown colour, but the tips of the guard hairs may fade to yellow or tan. The females are less robust at the chest, neck and shoulders than the adult males. Pups are born black, but become lighter during the first few years. Males range from 150 to 200 cm long and weigh about 146 kg. Females are about 240 cm long and weigh about 50 kg.[2]

Reproduction[edit]

Breeding behavior is very territorial, especially the males who fight to maintain their territory. Females mate within their territory of the resident male. Mating season occurs during November and December which is only done once a year. The pregnancy lasts for a little less than a year. The females gives birth to only one pup, and nurses them from about 8 to 12 months.[2]

References[edit]

  1. ^ Aurioles, D. & Trillmich, F. (2008). Arctocephalus philippii. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 30 January 2009.
  2. ^ a b c Handysides, Daniel. "Arctocephalus philippii Juan Fernandez fur seal". University of Michigan Museum of Zoology. ADW. 
  • Randall R. Reeves, Brent S. Stewart, Phillip J. Clapham and James A. Powell (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf, Inc. ISBN 0375411410. 
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