GUADALUPE FUR SEAL
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Male And Females With Pup |
Distinctive characteristics
Adult Guadalupe fur
seals are dark brown or dusty gray with yellowish silver manes, called guard
hairs, on the back of the neck. Guadalupe fur seals are sexually dimorphic in
size, as males are much larger and heavier than females; males can grow to
about seven feet in length and weigh upwards of 400 pounds, while females are
typically only five feet long and weigh about 110 pounds. Additionally,
males usually have a larger head and are lighter brown in color. Both males and
females have a twenty-year lifespan. Guadalupe fur seals have distinctive ear flaps
and large flippers for walking on land, confirming that they are not phocids (true
seals) but are more closely related to sea
lions. Guadalupe fur seal pups are born with black coats
similar to those of adult Guadalupe fur seals, but it is difficult to
distinguish juvenile Guadalupe fur seals from juveniles of California sea lions and Northern
fur seals due to physiological similarities.
Little is known about Guadalupe fur seals because they are a
pelagic species, meaning they spend most of their time in the open ocean. As a
member of the otariid, or sea lion, family, these fur seals have long external
ear flaps as well as large front flippers that allow them to walk on land.
Guadalupe fur seals are similar to northern fur seals in
appearance but are slightly smaller and have a more elongated snout. Adult male
Guadalupe fur seals also have a larger head and are lighter brown. Males and females
differ slightly in size. By looks alone, juvenile Guadalupe fur seals are very
difficult to tell apart from juvenile California sea lions and northern fur
seals.
Dental formula I 3/2, C 1/1, PC 6/5.
Size
Males can be as large as 2.1 m and 270
kg. Females can be up to 1.5 m and 50 kg or more. New-born weigh 5.4-6 kg, and
are 60-65 cm long.
Life Span
Females live almost twice as long as males, on average about 23 years compared to the male average life span of 13 years.
Gestation Period 365 days.
Can be confused with
Northern fur seals can be confused
with three other otariid species in their range: the Guadalupe fur seal, and
California and Steller sea lions. Coloration of Guadalupe and northern fur
seals is similar. Guadalupe fur seals have fur on the dorsum of the fore
flipper beyond the wrist, proportionately shorter rear flippers that only have
moderate length cartilaginous extensions, and a long tapering muzzle with a
bulbous nose that makes the muzzle seem slightly-upturned on the end.
Distinguishing females and young can be difficult if not seen well.
At sea, both species of fur seal can
be seen actively grooming while at the surface. Guadalupe fur seals will rest
in a posture characteristic of fur seals of the genus Arctocephalus with
the head down and both rear flippers held in the air and apart forming a ‘Y’
shape. Northern fur seals do not use this posture and routinely sleep in a ‘jug
handle’ position with palm of one fore flipper draped over the soles of the
hind flippers which are rotated forward to meet the fore flipper. Other fur
seal species of the genus Arctocephalus use this posture, so
it is possible that Guadalupe fur seals use it as well, although it has not
been described for the species. The head is often held up at approximately a
45° angle while the seal is in this position.
Northern fur seals can be readily separated from both sea lions, based on differences in pelage density and coloration, overall size, length and lack of fur on the top of the fore flippers beyond the wrist, head and muzzle shape, and relative size and prominence of the ear pinnae. In California sea lions the muzzle tapers to a blunt end, and the first toe or hallux is larger and longer than all of the other toes. Adult female, sub adult, and juvenile California sea lions are tan to pale brown and much lighter in coloration than northern fur seals. Only adult and sub adult male California sea lions become dark brown and are similar in color to northern fur seal bulls. However, dark male sea lions have a sagittal crest in contrast to the head of northern fur seal bulls that is slightly domed and lacks a conspicuous sagittal crest. California sea lion bulls lack the light tipped hairs in their much shorter mane. The loud repetitive bark of male California sea lions is distinctive and different from all northern fur seal vocalizations. Steller sea lions are very large with a massive head, blunt thick muzzle, stocky body, pale color, and short fur, and should never present an identification problem with northern fur seals.
Distribution
Northern fur seals are a widely-distributed pelagic species in the waters of the North Pacific Ocean and the adjacent, Bering Sea, Sea of Okhotsk, and Sea of Japan. They range from Northern Baja California, Mexico north and offshore across the North Pacific to Northern Honshu, Japan. The southern limit of their distribution at sea across the North Pacific is approximately 35° N. Vagrants reach the Yellow Sea in the west and eastern Beaufort Sea in the Arctic. The vast majority of the population breeds on the Pribilof Islands, with substantial numbers on the Commander Islands as well. Still other sites are used, including San Miguel Island in California, Bogoslof Island in the Bering Sea, and Robben Island off Sakhalin Island in Russia. Numerous other sites were formerly occupied and may still be visited. Rookeries are inhabited in summer and fall. These oceanic pinnipeds spend most of the year at sea, rarely (if ever) returning to land until the beginning of the next breeding season. Many animals, especially juveniles, migrate from the Bering Sea south to southern California or the waters off Japan, to spend the winter feeding.
Ecology and behavior
This is a highly polygynous species.
Males arrive at the rookeries up to one month before females and vocalize,
display and fight to establish and maintain territories. Breeding on the
Pribilof Islands occurs from mid-June through August, with a peak in early July
(the median date in southern California is approximately 2 weeks earlier than
at the Pribilofs). Northern fur seals become sexually mature at 3-5 years old,
at which time females usually produce one pup a year for most of the rest of
their lives. Males do not become physically mature, and large enough to compete
for a territory that will be used by females, until they are 8-9.
Northern fur seals usually give
birth a day after arrival at the rookery. Mean time from birth to estrous is
5.3 days, and 8.3 days for departure on the first feeding trip. Females breed
at the Pribilof Islands relatively far from the foraging areas at the edge of
the continental shelf and consistently make longer foraging trips than most
other female otariids, with a mean trip length of 6.9 days. Once foraging
begins the mean depth of dives is 68 m and duration is 2.2 minutes with maximum
depth recorded of 207 m, and duration of 7.6 minutes. Pups are visited 8-12 times
and attended for a mean of 2.1 days before being abruptly weaned at 4 months
old.
Northern fur seals are one of the
most pelagic pinnipeds. Adults are at sea most of the year, only coming ashore
for the breeding season for 35 and 45 days (on average) for adult females and
males respectively. They do not haul-out between breeding seasons, and once
weaned, juveniles go to sea and do not haul-out until they return, usually to
the island of their birth, 2-3 years later. At sea, northern fur seals are most
likely to be encountered alone or in pairs, with groups of 3 or more being
uncommon. They forage relatively far from shore, over the edge of the
continental shelf and slope. Diving is very active at dawn and dusk. Northern
fur seals spend quite a bit of time rafting at the surface, either asleep or
grooming. They employ a wide variety of resting postures, including raising one
or more flippers into the air, and draping one of their fore flippers over both
of the rear flippers to form a posture known as the ‘jug handle’ position.
Predators include killer whales, sharks, and Steller sea lions.
Predation
Historically in the 1700 and 1800s, Guadalupe fur seals were heavily hunted by commercial sealers. Currently, by-catch data is not available for the Guadalupe fur seal, however there have been documented injuries due to entanglement. The major cause of the Guadalupe fur seal's decline was commercial hunting in the late 18th and early 19th centuries. The species was exterminated in southern California waters by 1825. Commercial sealing continued in Mexican waters through 1894.
Feeding and prey
The diet varies by location and season, and includes many varieties of epipelagic and vertically-migrating mesopelagic schooling and non-schooling fish and squid. Prey species of importance in the waters off California and Washington include anchovy, hake, and saury, several species of squid and rockfish, and salmon. In Alaskan waters, walleye Pollock, capelin, sand lance, herring, Atka mackerel, and several species of squid are important prey.
Exploitation
The species was considered extinct
after most of the population was killed in 1928 but it was rediscovered in
1954. The Guadalupe fur seal is now fully protected by Mexican national
legislation, the Isla de Guadalupe having been declared a pinniped sanctuary in
1975. It is protected in the U.S. portion of its range by Californian law, as a
Threatened species under the U.S. Endangered Species Act, and as a Depleted and
Strategic species under the U.S. Marine Mammal Protection Act.
According to the ICUN List of Threatened Species, the
reduction of this species took place more than three generations (30 years)
ago, and its population is now increasing. It is restricted to a single
location during the breeding season, but there are no immediately obvious
threats that seem likely to drive it to Critically Endangered or even Extinct
in a very short time period; it is, however, close to meeting criterion D2 for
Vulnerable, and so it is listed as Near Threatened.
Threats and status
Northern fur seals have one of the
longest and most complex histories of commercial harvesting, which began when
the main breeding colonies were discovered in the late 18th century, and lasted
until 1984. Numerous international treaties and agreements were put in force in
efforts to manage this species. There were many periods of decline and recovery
over this long period. It is estimated that the population numbered up to 2.5
million animals in the 1950s. They may have been considerably more numerous
than this recent high level, when there were many more active rookeries before
the onset of exploitation by Europeans and Americans. The current population is
estimated at 1.3-1.5 million and is declining.
Entanglements in commercial fisheries, and in derelict and discarded fishing gear and marine debris, have caused significant annual mortality in the past. This mortality was highest during the period of active high seas drift net fishing in the North Pacific in the 1980s. Entanglement in debris is ongoing and affects juveniles and sub adults more than adults. Northern fur seals compete for walleye Pollock with one of the largest commercial fisheries world. Mortality from interactions with numerous fisheries and entanglement in debris, large annual harvests of prey species in commercial fisheries, long-term ecosystem regime change in the North Pacific, and possible changes in the foraging patterns of a key predator (the killer whale), may all be working synergistically to cause the current population decline.
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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