Fur seal

Fur seal
	A group of brown fur seals (Arctocephalus pusillus)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Clade:	Pinnipedia
Family:	Otariidae
Subfamily:	Arctocephalinae ; Scheffer & Rice 1963
Genera
	Arctocephalus ; Callorhinus

Last updated January 29, 2024

Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family Otariidae. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively long and muscular foreflippers, and the ability to walk on all fours. They are marked by their dense underfur, which made them a long-time object of commercial hunting. Eight species belong to the genus Arctocephalus and are found primarily in the Southern Hemisphere, while a ninth species also sometimes called fur seal, the Northern fur seal (Callorhinus ursinus), belongs to a different genus and inhabits the North Pacific. The fur seals in Arctocephalus are more closely related to sea lions than they are to the Northern fur seal, but all three groups are more closely related to each other than they are to true seals.

Taxonomy

Fur seal ranges Arctocephalinae.png — Fur seal ranges

Fur seals and sea lions make up the family Otariidae. Along with the Phocidae and Odobenidae, ottariids are pinnipeds descending from a common ancestor most closely related to modern bears (as hinted by the subfamily Arctocephalinae, meaning "bear-headed"). The name pinniped refers to mammals with front and rear flippers. Otariids arose about 15-17 million years ago in the Miocene, and were originally land mammals that rapidly diversified and adapted to a marine environment, giving rise to the semiaquatic marine mammals that thrive today. Fur seals and sea lions are closely related and commonly known together as the "eared seals". Until recently, fur seals were all grouped under a single subfamily of Pinnipedia, called the Arctocephalinae, to contrast them with Otariinae – the sea lions – based on the most prominent common feature, namely the coat of dense underfur intermixed with guard hairs. Recent genetic evidence, however, suggests Callorhinus is more closely related to some sea lion species, and the fur seal/sea lion subfamily distinction has been eliminated from many taxonomies. Nonetheless, all fur seals have certain features in common: the fur, generally smaller sizes, farther and longer foraging trips, smaller and more abundant prey items, and greater sexual dimorphism. For these reasons, the distinction remains useful. Fur seals comprise two genera: Callorhinus, and Arctocephalus. Callorhinus is represented by just one species in the Northern Hemisphere, the northern fur seal (Callorhinus ursinus), and Arctocephalus is represented by eight species in the Southern Hemisphere. The southern fur seals comprising the genus Arctocephalus include Antarctic fur seals, Galapagos fur seals, Juan Fernandez fur seals, New Zealand fur seals, brown fur seals, South American fur seals, and subantarctic fur seals.

Image	Name	Distribution
	Arctocephalus É. Geoffroy Saint-Hilaire & F. Cuvier in F. Cuvier, 1826	Antarctic fur seal, A. gazella Brown fur seal, A. pusillus South African fur seal, A. pusillus pusillus Australian fur seal, A. pusillus doriferus Galápagos fur seal, A. galapagoensis Guadalupe fur seal, A. townsendi Juan Fernández fur seal, A. philippii New Zealand fur seal or southern fur seal, A. forsteri South American fur seal, A. australis Subantarctic fur seal, A. tropicalis
	Callorhinus Gray, 1859	Northern fur seal, C. ursinus

Physical appearance

Along with the previously mentioned thick underfur, fur seals are distinguished from sea lions by their smaller body structure, greater sexual dimorphism, smaller prey, and longer foraging trips during the feeding cycle. The physical appearance of fur seals varies with individual species, but the main characteristics remain constant.

Fur seals are characterized by their external pinnae, dense underfur, vibrissae, and long, muscular limbs. They share with other otariids the ability to rotate their rear limbs forward, supporting their bodies and allowing them to ambulate on land. In water, their front limbs, typically measuring about a fourth of their body length, act as oars and can propel them forward for optimal mobility. The surfaces of these long, paddle-like fore limbs are leathery with small claws. Otariids have a dog-like head, sharp, well-developed canines, sharp eyesight, and keen hearing.

They are extremely sexually dimorphic mammals, with the males often two to five times the size of the females, with proportionally larger heads, necks, and chests. Size ranges from about 1.5 m, 64 kg in the male Galapagos fur seal (also the smallest pinniped) to 2.5 m, 180 kg in the adult male New Zealand fur seal. Most fur seal pups are born with a black-brown coat that molts at 2–3 months, revealing a brown coat that typically gets darker with age. Some males and females within the same species have significant differences in appearance, further contributing to the sexual dimorphism. Females and juveniles often have a lighter colored coat overall or only on the chest, as seen in South American fur seals. In a northern fur seal population, the females are typically silvery-gray on the dorsal side and reddish-brown on their ventral side with a light gray patch on their chest. This makes them easily distinguished from the males with their brownish-gray to reddish-brown or black coats.

Habitat

Of the fur seal family, eight species are considered southern fur seals, and only one is found in the Northern Hemisphere. The southern group includes Antarctic, Galapagos, Guadalupe, Juan Fernandez, New Zealand, brown, South American, and subantarctic fur seals. They typically spend about 70% of their lives in subpolar, temperate, and equatorial waters. Colonies of fur seals can be seen throughout the Pacific and Southern Oceans from south Australia, Africa, and New Zealand, to the coast of Peru and north to California. They are typically nonmigrating mammals, with the exception of the northern fur seal, which has been known to travel distances up to 10,000 km. Fur seals are often found near isolated islands or peninsulas, and can be seen hauling out onto the mainland during winter. Although they are not migratory, they have been observed wandering hundreds of miles from their breeding grounds in times of scarce resources. For example, the subantarctic fur seal typically resides near temperate islands in the South Atlantic and Indian Oceans north of the Antarctic Polar Front, but juvenile males have been seen wandering as far north as Brazil and South Africa.

Behavior and ecology

Typically, fur seals gather during the summer in large rookeries at specific beaches or rocky outcrops to give birth and breed. All species are polygynous, meaning dominant males reproduce with more than one female. For most species, total gestation lasts about 11.5 months, including a several-month period of delayed implantation of the embryo. Northern fur seal males aggressively select and defend the specific females in their harems.^[1] Females typically reach sexual maturity around 3–4 years. The males reach sexual maturity around the same time, but do not become territorial or mate until 6–10 years.

The breeding season typically begins in November and lasts 2–3 months. The northern fur seals begin their breeding season as early as June due to their region, climate, and resources. In all cases, the males arrive a few weeks early to fight for their territory and groups of females with which to mate. They congregate at rocky, isolated breeding grounds and defend their territory through fighting and vocalization. Males typically do not leave their territory for the entirety of the breeding season, fasting and competing until all energy sources are depleted.

The Juan Fernandez fur seals deviate from this typical behavior, using aquatic breeding territories not seen in other fur seals. They use rocky sites for breeding, but males fight for territory on land and on the shoreline and in the water. Upon arriving to the breeding grounds, females give birth to their pups from the previous season. About a week later, the females mate again and shortly after begin their feeding cycle, which typically consists of foraging and feeding at sea for about 5 days, then returning to the breeding grounds to nurse the pups for about 2 days. Mothers and pups locate each other using call recognition during nursing period. The Juan Fernandez fur seal has a particularly long feeding cycle, with about 12 days of foraging and feeding and 5 days of nursing. Most fur seals continue this cycle for about 9 months until they wean their pup. The exception to this is the Antarctic fur seal, which has a feeding cycle that lasts only 4 months. During foraging trips, most female fur seals travel around 200 km from the breeding site, and can dive around 200 m depending on food availability.

The remainder of the year, fur seals lead a largely pelagic existence in the open sea, pursuing their prey wherever it is abundant. They feed on moderately sized fish, squid, and krill. Several species of the southern fur seal also have sea birds, especially penguins, as part of their diets.^[2]^[3] Fur seals, in turn, are preyed upon by sharks, orcas, and occasionally by larger sea lions. These opportunistic mammals tend to feed and dive in shallow waters at night, when their prey are swimming near the surface. South American fur seals exhibit a different diet; adults feed almost exclusively on anchovies, while juveniles feed on demersal fish, most likely due to availability.

When fur seals were hunted in the late 18th and early 19th centuries, they hauled out on remote islands where no predators were present. The hunters reported being able to club the unwary animals to death one after another, making the hunt profitable, though the price per seal skin was low.^[4]

Population and survival

The average lifespan of fur seals varies with different species from 13 to 25 years, with females typically living longer. Most populations continue to expand as they recover from previous commercial hunting and environmental threats. Many species were heavily exploited by commercial sealers, especially during the 19th century, when their fur was highly valued. Beginning in the 1790s, the ports of Stonington and New Haven, Connecticut, were leaders of the American fur seal trade, which primarily entailed clubbing fur seals to death on uninhabited South Pacific islands, skinning them, and selling the hides in China.^[4] Many populations, notably the Guadalupe fur seal, northern fur seal, and Cape fur seal, suffered dramatic declines and are still recovering. Currently, most species are protected, and hunting is mostly limited to subsistence harvest. Globally, most populations can be considered healthy, mostly because they often prefer remote habitats that are relatively inaccessible to humans. Nonetheless, environmental degradation, competition with fisheries, and climate change potentially pose threats to some populations.

Related Research Articles

<span class="mw-page-title-main">Earless seal</span> Family of mammals

The earless seals, phocids, or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae. They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.

An eared seal, otariid, or otary is any member of the marine mammal family Otariidae, one of three groupings of pinnipeds. They comprise 15 extant species in seven genera and are commonly known either as sea lions or fur seals, distinct from true seals (phocids) and the walrus (odobenids). Otariids are adapted to a semiaquatic lifestyle, feeding and migrating in the water, but breeding and resting on land or ice. They reside in subpolar, temperate, and equatorial waters throughout the Pacific and Southern Oceans, the southern Indian, and Atlantic Oceans. They are conspicuously absent in the north Atlantic.

The California sea lion is a coastal eared seal native to western North America. It is one of six species of sea lions. Its natural habitat ranges from southeast Alaska to central Mexico, including the Gulf of California. California sea lions are sexually dimorphic; males are larger than females, and have a thicker neck, and a protruding sagittal crest. They mainly haul-out on sandy or rocky beaches, but they also frequent manmade environments such as marinas and wharves. California sea lions feed on a number of species of fish and squid, and are preyed on by orcas and great white sharks.

Sea lions are pinnipeds characterized by external ear flaps, long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the fur seals, they make up the family Otariidae, eared seals. The sea lions have six extant and one extinct species in five genera. Their range extends from the subarctic to tropical waters of the global ocean in both the Northern and Southern Hemispheres, with the notable exception of the northern Atlantic Ocean. They have an average lifespan of 20–30 years. A male California sea lion weighs on average about 300 kg (660 lb) and is about 2.4 m (8 ft) long, while the female sea lion weighs 100 kg (220 lb) and is 1.8 m (6 ft) long. The largest sea lions are Steller's sea lions, which can weigh 1,000 kg (2,200 lb) and grow to a length of 3.0 m (10 ft). Sea lions consume large quantities of food at a time and are known to eat about 5–8% of their body weight at a single feeding. Sea lions can move around 16 knots in water and at their fastest they can reach a speed of about 30 knots. Three species, the Australian sea lion, the Galápagos sea lion and the New Zealand sea lion, are listed as endangered.

Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semi-aquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.

<span class="mw-page-title-main">Steller sea lion</span> Species of carnivore

The Steller sea lion is a large, near-threatened species of sea lion, predominantly found in the coastal marine habitats of the northeast Pacific Ocean and the Pacific Northwest regions of North America, from north-central California to Oregon, Washington and British Columbia to Alaska. Its range continues across the Northern Pacific and the Aleutian Islands, all the way to Kamchatka, Magadan Oblast, and the Sea of Okhotsk, south to Honshu's northern coastline. It is the sole member of the genus Eumetopias, and the largest of the so-called eared seals (Otariidae). Among pinnipeds, only the walrus and the two species of elephant seal are bigger. The species is named for the naturalist and explorer Georg Wilhelm Steller, who first described them in 1741. Steller's sea lions have attracted considerable attention in recent decades, both from scientists and the general public, due to significant declines in their numbers over an extensive portion of their northern range—notably in Alaska.

The leopard seal, also referred to as the sea leopard, is the second largest species of seal in the Antarctic. Its only natural predator is the orca. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".

Elephant seals or sea elephants are very large, oceangoing earless seals in the genus Mirounga. Both species, the northern elephant seal and the southern elephant seal, were hunted to the brink of extinction for oil by the end of the 19th century, but their numbers have since recovered. They are the largest extant carnivorans, weighing up to 5,000 kilograms (11,000 lb). Despite their name, elephant seals are not closely related to elephants, and the large proboscis or trunk that males have was convergently evolved.

The northern fur seal is an eared seal found along the north Pacific Ocean, the Bering Sea, and the Sea of Okhotsk. It is the largest member of the fur seal subfamily (Arctocephalinae) and the only living species in the genus Callorhinus. A single fossil species, Callorhinus gilmorei, is known from the Pliocene of Japan and western North America.

The Antarctic fur seal is one of eight seals in the genus Arctocephalus, and one of nine fur seals in the subfamily Arctocephalinae. Despite what its name suggests, the Antarctic fur seal is mostly distributed in Subantarctic islands and its scientific name is thought to have come from the German vessel SMS Gazelle, which was the first to collect specimens of this species from Kerguelen Islands.

The subantarctic fur seal is a species of arctocephaline found in the southern parts of the Indian, Pacific, and Atlantic Oceans. It was first described by Gray in 1872 from a specimen recovered in northern Australia—hence the inappropriate specific name tropicalis.

The Guadalupe fur seal is one of eight members of the fur seal genus Arctocephalus. They are the northernmost member of this genus. Sealers reduced the population to just a few dozen by the late 19th century, but the species had recovered to 10,000 in number by the late 1990s. Many individuals can be found on Mexico's Guadalupe Island.

The Juan Fernández fur seal is the second smallest of the fur seals, second only to the Galápagos fur seal. They are found only on the Pacific Coast of South America, more specifically on the Juan Fernández Islands and the Desventuradas Islands. There is still much that is unknown about this species. Scientists still do not know the average life span of this species, or the diet and behavior of males apart from the breeding season.

The Galápagos fur seal is one of eight seals in the genus Arctocephalus and one of nine seals in the subfamily Arctocephalinae. It is the smallest of all of the eared seals. They are endemic to the Galápagos Islands in the eastern Pacific. The total estimated population as of 1970 was said to be about 30,000, although the population has been said to be on the decline since the 1980s due to environmental factors such as pollution, disease, invasive species, and their limited territory. Due to the population having been historically vulnerable to hunting, the Galápagos fur seal has been protected by the Ecuadorian government since 1934

The brown fur seal, also known as the Cape fur seal, South African fur seal and Australian fur seal, is a species of fur seal.

The South American sea lion, also called the southern sea lion and the Patagonian sea lion, is a sea lion found on the western and southeastern coasts of South America. It is the only member of the genus Otaria. The species is highly sexually dimorphic. Males have a large head and prominent mane. They mainly feed on fish and cephalopods and haul out on sand, gravel, rocky, or pebble beaches. In most populations, breeding males are both territorial and harem holding; they establish territories first and then try to herd females into them. The overall population of the species is considered stable, estimated at 265,000 animals.

The Australian sea lion, also known as the Australian sea-lion or Australian sealion, is a species of sea lion that is the only endemic pinniped in Australia. It is currently monotypic in the genus Neophoca, with the extinct Pleistocene New Zealand sea lion Neophoca palatina the only known congener. With a population estimated at 14,730 animals, the Wildlife Conservation Act of Western Australia (1950) has listed them as “in need of special protection”. Their Conservation status is listed as endangered. These pinnipeds are specifically known for their abnormal breeding cycles, which are varied between a 5-month breeding cycle and a 17-18 month aseasonal breeding cycle, compared to other pinnipeds which fit into a 12-month reproductive cycle. Females are either silver or fawn with a cream underbelly and males are dark brown with a yellow mane and are bigger than the females.

Arctocephalus forsteri is a species of fur seal found mainly around southern Australia and New Zealand. The name New Zealand fur seal is used by English speakers in New Zealand; kekeno is used in the Māori language. As of 2014, the common name long-nosed fur seal has been proposed for the population of seals inhabiting Australia.

The South American fur seal breeds on the coasts of Peru, Chile, the Falkland Islands, Argentina, Uruguay and Brazil. The total population is around 250,000. However, population counts are sparse and outdated. Although Uruguay has long been considered to be the largest population of South American fur seals, recent census data indicates that the largest breeding population of A. a. australis are at the Falkland Islands followed by Uruguay. The population of South American fur seals in 1999 was estimated at 390,000, a drop from a 1987 estimate of 500,000 - however a paucity of population data, combined with inconsistent census methods, makes it difficult to interpret global population trends.

The southern elephant seal is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. It gets its name from its massive size and the large proboscis of the adult male, which is used to produce very loud roars, especially during the breeding season. A bull southern elephant seal is about 40% heavier than a male northern elephant seal, which is nearly twice the weight of a male walrus, or 6–7 times heavier than the largest living mostly terrestrial carnivorans, the Kodiak bear and the polar bear.

References

↑ Fur Seals (Arctocephalinae). afsc.noaa.gov
↑ Daneri, G. A.; Carlini, A. R.; Harrington, A.; Balboni, L.; Hernandez, C. M. (2008). "Interannual variation in the diet of non-breeding male Antarctic fur seals, Arctocephalus gazella, at Isla 25 de Mayo/King George Island". Polar Biology. 31 (11): 1365. doi:10.1007/s00300-008-0475-3. hdl: 11336/135116 . S2CID 13332236.
↑ Nigel W Bonner, S Hunter (1982). "Predatory interactions between Antarctic fur seals, macaroni penguins and giant petrels" (PDF). British Antarctic Survey Bulletin. 56: 75–79. Archived from the original (PDF) on 2012-10-31.
1 2 Muir, Diana, "Reflections in Bullough's Pond", University Press of New England, 2000, pp. 80ff ISBN 0-87451-909-8.