JUAN FERNANDEZ FUR SEAL
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Adult Male Female And Pup |
Distinctive characteristics
Juan Fernandez fur seals are sexually
dimorphic, with males about 1.4 times longer and approximately 3 times heavier
than adult females. Juan Fernandez fur seals have thick pelage, with dense
underfur. Adults have moderate length whitish-cream vibrissae and long
prominent ear pinnae.
Adult
males have a rounded crown with the apex above the ear pinnae. There is a
slight rounded forehead where the crown meets the base of muzzle. The muzzle is
long, straight, somewhat flattened on top, and tapers in width and thickness to
the fleshy nose on the end. The black naked skin of the nose, or rhinarium, is
large and somewhat bulbous and the nares orient downward. The large rhinarium
gives the muzzle a slight upturned look at the end, especially in males. The
mane extends to the crown, and the long erect guard hairs on the head
accentuate the crown and forehead. This is especially noticeable where the
longer fur of the crown meets the shorter, more swept-back, fur of the muzzle
between the eyes. From the crown, the long coarse guard hairs of the mane cover
the nape and neck to the shoulders, and on the sides and undersides of the neck
from throat to chest. The neck, chest and shoulders to the fore flippers are
enlarged with muscle and fat. The abdomen is much smaller, and tapers to the
narrow pelvis. The canine teeth of adult males are larger and thicker than
those of females.
Adult
females, sub adults, and juveniles also have a long tapering muzzle, with nares
angled slightly downward. However, because the rhinarium is not enlarged, the
muzzle is more pointed. The crown is slightly domed, giving the head a rounded
look in profile. The ear pinnae are long and stand out from the head enough to
make them conspicuous. The mane is absent and the neck and shoulders are in
proportion with the rest of the body.
The fore
flippers have a dark, sparse, short fur that extends beyond the wrist onto the
middle of the dorsal surface of the flipper in a ‘V’ pattern that does not
reach the rounded tip. The rest of the dorsal surface, and the palms of both
fore flippers are covered with a hairless black leathery skin. The first digit
is the longest, widest and thickest, and curves posteriorly, giving the flipper
a swept-back look. Digits 2-5 are successively shorter. There is a small
opening in the skin at the end of each digit for a claw that is usually reduced
to a vestigial nodule, and rarely emerges above the skin. The claw openings are
set back from the free edge of the flippers by cartilaginous rods that extend
the length of each digit, and expand the size of the flippers.
The hind
flippers have dark, short, sparse hair covering part of the proximal end of the
flipper, and the rest of the dorsal surface, and the entire sole is covered in
black leathery hairless skin. The hind flippers are long and each digit has a
cartilaginous rod that adds a flap-like extension to each toe. The bones of the
three central toes terminate at the position of the small nails that emerge
through the skin on the dorsal surface, set back from the end of the flipper.
The claws of digits 1 and 5 are vestigial, like the claws on the fore flippers,
and may or may not emerge from small openings set back from the end of the
flaps. All of the flaps at the end of the flipper are of relatively equal
length. The first toe or hallux and the fifth toe are somewhat wider than toes
2–4.
Coloration
of adult males is dark grayish brown to grayish black. The longer guard hairs
of the mane are light tipped off-white to ginger on the crown, nape and, to a
variable extent, on the sides and back of the neck, creating a grizzled
appearance. Adult males have scars from fighting, and some are heavily scarred.
Adult females, sub adults, and juveniles are dark brown to grayish-black above
and paler in variable patterns below, especially on the chest and underside of
the neck, which can be tan to creamy gray. Both sexes have a variable amount of
lighter buff to reddish brown color on the muzzle, which often extends into the
face above the eyes. Pups are born in a black wooly coat.
Dental formula I 3/2, C 1/1, PC 6/5.
Size
Adult males are estimated to be 2 m long and weigh 140 kg. A series of lactating females, combined from several years, were an average of 1.42 m long and weighed an average of 48.1 kg. New-born pups are approximately 65-68 cm and 6.2-6.9 kg.
Life Span
Males may live over 13 years while females may live up to 23 years.
Gestation Period 365 days.
Can be confused with
South American, Antarctic, and Sub
Antarctic fur seals, and South American sea lions have distributions that bring
them near to the range of Juan Fernandez fur seals. Sub Antarctic and Antarctic
fur seals have been recorded from the Juan Fernandez Islands, and Juan
Fernandez fur seals occur as vagrants along the coast of Chile.
Adult male
Juan Fernandez fur seals have a longer muzzle, distinctive bulbous rhinarium,
and unique coloration of the crown, nape and upper neck that separate them from
Antarctic and South American fur seals. Separating adult female, sub adult, and
juvenile southern fur seal species at a distance is usually difficult and often
impossible without extensive experience with the species in question. In
general, adult female Juan Fernandez fur seals are longer and heavier than
female Antarctic, Sub Antarctic, and South American fur seals, and have
downward oriented nares, and a more rounded crown.
Sub
Antarctic fur seals are uniquely colored. The back and rump of adult males is
dark gray to brownish black, and the chest and neck through the muzzle, face
and area around the eyes are cream with yellow to orange shading. The ear
pinnae are short, mostly bare skin and dark, and attach in the dark pelage of
the upper parts. There is also a tuft of longer pale fur in the dark crown
above the eyes and behind the dark forehead. Although the adult male is
enlarged and thick in the shoulders and neck, he does not have a mane. Adult
females have similar coloration to the males, but have less well-defined pale
facial markings that can be shaded with dull yellow orange to light brown. In
both sexes the top of the fore flippers is darker as is the area where the
flippers attach to the sides. The underside of the abdomen is dark ginger to
reddish brown. The fore flippers and hind flippers are proportionately short
and wide.
South
American sea lions have large, blocky heads with a short muzzle that is blunt
on the end, and smallish inconspicuous ear pinnae. They are also pale tan to
light golden brown, with sleek fur that is not dense or shaggy, except in the
case of the mane on the otherwise unmistakable adult males, and are heavy
bodied.
Distribution
The
Juan Fernandez fur seal is only
found ashore regularly in the Juan Fernandez Archipelago in the eastern South
Pacific, west of Chile. The Archipelago includes the Juan Fernandez Island
group, and the San Felix Islands, approximately 600 km to the north. Vagrant
Juan Fernandez fur seals have been
found on the west coast of South America from southern Peru to southern Chile.
When ashore, these fur seals prefer rocky and volcanic shorelines with
boulders, grottos, overhangs and caves. The Juan
Fernandez fur seal is only found ashore regularly in the Juan Fernandez
Archipelago in the eastern South Pacific, west of Chile. The Archipelago
includes the Juan Fernandez Island group, and the San Felix Islands,
approximately 600 km to the north. Vagrant Juan Fernandez fur seals have been
found on the west coast of South America from southern Peru to southern Chile.
When ashore, these fur seals prefer rocky and volcanic shorelines with
boulders, grottos, overhangs, and caves.
Ecology and behavior
The Juan Fernandez fur seal is a polygynous
species. The breeding season lasts from mid-November to the end of January, and
the colonies are essentially vacated by early September (based on the
observations of sealers from the late 18th century), and no
later than mid-October.
Males
defend territories that are typically around 36 m2 in size and that have an
average of 4 females. Most adult females give birth within a few days of
arriving at the rookery. Mean time from birth to departure on the first
foraging trip is 11.3 days. Juan Fernandez fur seal females travel long
distances to find adequate quantities of prey and, on average, have the longest
foraging trips of any otariid. Although females can be gone for as little as 1
day, the mean is 12.3 days per foraging trip and the longest trip recorded
lasted 25 days. Mean length of pup attendance is 5.3 days with a range of
0.3–15.8 days. Based on the onset of pupping and the observations of vacant
colonies in early September, it has been calculated that pups are weaned in
7-10 months.
Juan
Fernandez fur seals travel long distances to their foraging areas. The mean
distance travelled away from the breeding colony is 653 km, and all tagged
females travelled at least 550 km to forage. Most trips were southwest and west
of the Juan Fernandez Islands, far offshore to deep oceanic areas. Despite
this, the mean depth of dive of 12.3 m, and the mean duration of 51 seconds is
shallow and short even for an otariid, and indicates surface feeding. The
deepest dives are made to 90–100 m and the longest dives are just over 6
minutes. Nearly all foraging dives occur at night.
At sea, these fur seals can be quite animated as they groom at the surface. They also rest in, and assume a number of postures including: head down with hind flippers elevated and swaying in the air, as is typical of many southern fur seals; asleep at the surface with both hind flippers tucked under a fore flipper in a ‘jug-handle’ position; and with both fore flippers or all 4 flippers held in the air. Little is known about predators, but blue and great white sharks are suspected, as are killer whales, and possibly the leopard seals that infrequently visit the islands.
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.
Feeding and prey
Juan Fernandez fur seals feed extensively on vertically-migrating prey at night. Their diet is one of the least diverse of any otariid, and along with the long foraging trips made by lactating females reflects the low productivity of their oceanic feeding areas. Foraging varies between years and probably reflects abundance and availability of prey. Myctophids are the most important fishes in the diet and onychoteuthid squid are the most important cephalopods.
Exploitation
Centuries
ago, the first sailors to encounter these seals in the Juan Fernández Islands
reported extremely large numbers of these seals. Unfortunately, the species was
very heavily exploited for its pelt, blubber, meat, and oil between the
17th-19th centuries and by the beginning of the 20th century it was believed to
be extinct.
In 1978, the species was given total protection by national
Chilean legislation. It remains listed as Near Threatened on the IUCN
Red List, due to its limited population size
and the resulting species’ low genetic diversity. The IUCN/SSC
Specialist group has recommended that research
be carried out into the diet of the species in order to determine if there is
any potential competition with fisheries. Entanglement in fishing nets and
plastic debris is also observed as a problem for this species.
Threats and status
Juan Fernandez fur seals were hunted
to the brink of extinction by commercial sealers trading pelts in China.
Intensive sealing began in the late 18th century and ended in
the late 19th century, when few could be found. It is likely
that several million seals were killed during this period. Small numbers were
seen in the early 20th century, but the species was thought to
have gone extinct shortly thereafter. The species was rediscovered in the
middle of the 20th century and has since been making a slow
comeback. Following the 1990-91 breeding season the total population was
estimated to number 12,000 animals.
The
limited size of the population and the fact that the species passed through a
genetic bottleneck make this species vulnerable to catastrophic events and
stress from disease outbreaks, oil spills, environmental regime shift,
disturbance, and fisheries conflicts. No fisheries conflicts have been
identified to date. Individual seals have been seen with plastic bands around
their necks since 1982, but the level of mortality from these entanglements is
unknown.
Factors hypothesized include
The direct and indirect effects of
large-scale commercial fisheries on key prey species, long –term ecosystem shifts,
and changes in behavior by a primary predator, the killer whale, or a
combination of these factors.
IUCN status Near Threatened
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Adult Male and Female. |
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