Ear flaps of Otaria flavescens

The eared seals or otariids are marine mammals in the family Otariidae, one of three groupings of Pinnipeds. They comprise 16 species in seven genera commonly known either as sea lions or fur seals, distinct from true seals (phocids) and the Walrus (odobenids). Otariids are adapted to a semi-aquatic 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 and the southern Indian and Atlantic oceans. They are conspicuously absent in the north Atlantic.

The name otariid comes from the Greek otarion meaning "little ear",^[1] referring to the small but visible external ear flaps (pinnae) which can be used to distinguish them from the phocids.

Evolution and taxonomy

Along with the Phocidae and Odobenidae, the two other members of Pinnipedia, Otаriidae are descended from a common ancestor most closely related to modern bears.^[2] There remains debate as to whether the phocids diverged from the otariids before or after the Walrus.

Otariids arose in the late Miocene (10-12 million years ago) in the North Pacific, diversifying rapidly into the Southern Hemisphere where most species now live. Callorhinus (Northern Fur Seal) has the oldest fossil record of any extant Otariid, extending to the middle Pliocene, and probably arose from the extinct fur seal Thalassoleon.

Traditionally, otariids had been subdivided into the fur seal (Arctocephalinae) and sea lion (Otariinae) subfamilies, with the major distinction between them being the presence of a thick underfur layer in the former. Under this categorization, the fur seals comprised two genera: Callorhinus in the North Pacific with a single representative, the Northern Fur Seal (C. ursinus) and eight species in the southern hemisphere under the genus Arctocephalus, while the sea lions comprise five species under five genera.^[3] Recent analyses of the genetic evidence suggests that the Callorhinus ursinus is in fact more closely related to several sea lion species.^[4] Furthermore, many of the Otariinae appear to be more phylogenetically distinct than previously assumed; for example, the Japanese Sea Lion (Zalophus japonicus) is now considered a separate species, rather than a subspecies of the California Sea Lion (Zalophus californius). In light of this evidence, the subfamily separation has been removed entirely and the Otariidae family has been organized into seven genera with 16 species and two subspecies.^[5][6] Nonetheless, because of morphological and behavioral similarity among the "fur seals" and "sea lions", these remain useful categories when discussing differences between groups of species: 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. And all sea lions have certain features in common, in particular their coarse, short fur, greater bulk and larger prey than fur seals. For these reasons, the distinction remains useful

Anatomy and appearance

California Sea Lions

Otariids have proportionately much larger foreflippers and pectoral muscles than phocids, and have the ability to turn their hind limbs forward and walk on all fours, making them far more maneuverable on land. They are generally considered to be less adapted to an aquatic lifestyle, since they breed primarily on land and haul out more frequently than true seals. However, they can attain higher bursts of speed and greater maneuverability in the water. Their swimming power derives from the use of flippers more so than the sinuous whole body movements typical of phocids and walruses.

Otariids are further distinguished by a more dog-like head, sharp, well-developed canines and the aforementioned visible external pinnae. Their postcanine teeth are generally simple and conical in shape. The dental formula for eared seals is: . Sea lions are covered with coarse guard hairs, while fur seals have a thick underfur, which have historically made them the objects of commercial exploitation.

Male otariids range in size from the 70 kg (150 lbs) Galapagos Fur Seal, smallest of all pinnipeds, to the over 1000 kg (2200 lbs) Steller Sea Lion. Mature male otariids weigh two to six times more than females with proportionately larger heads, necks, and chests, making them the most sexually dimorphic of all mammals.^[7]

Behavior

All otariids breed on land during well-defined breeding seasons. Except for the Australian Sea Lion, which has an atypical 17.5 month breeding cycle, they form strictly annual aggregations on beaches or rocky substrates, often on islands. All species are polygynous; i.e. successful males breed with several females. In most species, males arrive at breeding sites first and establish and maintain territories through vocal and visual displays and occasional fighting. Females typically arrive on shore a day or so before giving birth. While considered social animals, there are no permanent hierarchies or statuses established on the colonies. The extent to which males control females or territories varies between species. Thus the Northern Fur Seal and the South American Sea Lion tend to herd specific harem-associated females, occasionally injuring them, while the Steller Sea Lion and the New Zealand Sea Lion control spatial territories but do not generally interfere with the movement of the females.

Otariids are carnivorous, feeding on fish, squid and krill. Sea lions tend to feed closer to shore in upwelling zones feeding on larger fish while the smaller fur seals tend to take longer, offshore foraging trips and can subsist on large numbers of smaller prey items. They are visual feeders and some females are capable of dives up to 400 m (1300 ft).

Species

• SUBORDER Pinnipedia
• Family Otariidae
  • Subfamily Arctocephalinae
    • Genus Arctocephalus
      • Antarctic Fur Seal, A. gazella
      • Guadalupe Fur Seal, A. townsendi
      • Juan Fernandez Fur Seal, A. philippii
      • Galapagos Fur Seal, A. galapagoensis
      • Brown Fur Seal, A. pusillus
        • South African Fur Seal, A. pusillus pusillus
        • Australian Fur Seal, A. pusillus doriferus
      • New Zealand Fur Seal or Southern Fur Seal, A. forsteri
      • Subantarctic Fur Seal, A. tropicalis
      • South American Fur Seal, A. australis
    • Genus Callorhinus
      • Northern Fur Seal, C. ursinus
  • Subfamily Otariinae
    • Genus Eumetopias
      • Steller Sea Lion, E. jubatus
    • Genus Neophoca
      • Australian Sea Lion, N. cinerea
    • Genus Otaria
      • South American Sea Lion, O. flavescens
    • Genus Phocarctos
      • New Zealand Sea Lion or Hooker's Sea Lion, P. hookeri
    • Genus Zalophus
      • California Sea Lion, Z. californianus
      • †Japanese Sea Lion, Z. japonicus - extinct (1950s)
      • Galapagos Sea Lion, Z. wollebaeki
• Family Phocidae: true seals
• Family Odobenidae: Walrus

Notes

Further reading

• Berta, A., and L. Sumich (1999) Marine Mammals: Evolutionary Biology. San Diego: Academic Press.
• Gentry, R. L (1998) Behavior and Ecology of the Northern Fur Seal. Princeton: Princeton University Press.
• Perrin, W. F., B. Würsig, and J. G. M. Thewissen (2002) Encyclopedia of Marine Mammals. San Diego: Academic Press.
• Riedman, M. (1990) The Pinnipeds: Seals, Sea Lions and Walruses. Berkeley: University of California Press.

Fur seals are any of nine species of pinnipeds in the Otariidae family. One species, the northern fur seal (Callorhinus ursinus) inhabits the North Pacific, while seven species in the Arctocephalus genus are found primarily in the Southern hemisphere. 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.

Taxonomy

Until recently, fur seals were all grouped under a single subfamily of Pinnipedia called 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 that Callorhinus is more closely related to some sea lion species, and the fur seal/sealion subfamily distinction has been eliminated from most 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.

Physical appearance

Fur seals share with other otariids the ability to turn their rear limbs forward and move on all fours. Fur seals are generally smaller than sea lions. At under 1 metre (3 ft 3 in), the Galapagos fur seal is the smallest of all pinnipeds. However, their flippers tend to be proportionately longer, their pelage tends to be darker and the vibrissae more prominent. Males are often more than five times heavier than the females, making them among the most sexually dimorphic of all mammal groups.

Behavior and ecology

A seal at Living Coasts sunbathing on a rock

A fur seal rookery with thousands of seals

Typically, fur seals gather during the summer months annually in large assemblages 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. While northern fur seal males aggressively select and defend the specific females in their harems,^[1] males of southern species of fur seal tend to protect spatial territories and females are free to choose or switch their mates according to their own preference or social hierarchy. After several continuous days of nursing the newborn pups, females go on extended foraging trips that can last as long as a week, returning to the rookery to feed their pups until they are weaned. Males fast during the reproductive season, unwilling to leave their females or territories.

The remainder of the year, fur seals lead a largely pelagic existence in the open sea pursuing their prey wherever it is abundant and plentiful. Fur seals 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 diet.^[2][3] The fur seals themselves are preyed upon by sharks, orcas and occasionally by larger sea lions.

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

Exploitation

Inuit people in seal fur coats

Fur Seal, Alaska Maritime National Wildlife Refuge

Many fur seal 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.^[5] 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 due to the fact that 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.

Species

• SUBORDER Pinnipedia
• Family Otariidae
  • Genus Arctocephalus
    • Antarctic Fur Seal, A. gazella
    • Brown Fur Seal, A. pusillus
      • South African Fur Seal, A. pusillus pusillus
      • Australian Fur Seal, A. pusillus doriferus
    • Galapagos Fur Seal, A. galapagoensis
    • Guadalupe Fur Seal, A. townsendi
    • Juan Fernandez 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
  • Genus Callorhinus
    • Northern Fur Seal, C. ursinus
  • Genus Eumetopias
  • Genus Neophoca
  • Genus Otaria
  • Genus Phocarctos
  • Genus Zalophus
• Family Phocidae: true seals
• Family Odobenidae: Walrus

See also

• Seal (disambiguation)
• Bering Sea Arbitration

References

1. ^ http://www.afsc.noaa.gov/NMML/education/Pinnipeds/furseals.htm
2. ^ http://www.springerlink.com/content/m2873042013t33h7/
3. ^ www.bas.ac.uk/documents/bas_bulletins/bulletin56_08.pdf
4. ^ Muir, Diana Reflections in Bullough's Pond, University Press of New England, 2001
5. ^ Muir, Diana, "Reflections in Bullough's Pond," University Press of New England, 2000,pp. 80ff.

v • d • e Extant Carnivora species Kingdom: Animalia · Phylum: Chordata · Class: Mammalia · Infraclass: Eutheria · Superorder: Laurasiatheria   Suborder Feliformia Nandiniidae Nandinia African Palm Civet (N. binotata) Herpestidae (Mongooses) Atilax Marsh Mongoose (A. paludinosus) Bdeogale Bushy-tailed Mongoose (B. crassicauda} · Jackson's Mongoose (B. jacksoni) · Black-footed Mongoose (B. nigripes) Crossarchus Alexander's Kusimanse (C. alexandri) · Angolan Kusimanse (C. ansorgei) · Common Kusimanse (C. obscurus) · Flat-headed Kusimanse (C. platycephalus) Cynictis Yellow Mongoose (C. penicillata) Dologale Pousargues's Mongoose (D. dybowskii) Galerella Angolan Slender Mongoose (G. flavescens) · Somalian Slender Mongoose (G. ochracea) · Cape Gray Mongoose (G. pulverulenta) · Slender Mongoose (G. sanguinea) Helogale Ethiopian Dwarf Mongoose (H. hirtula) · Common Dwarf Mongoose (H. parvula) Herpestes Short-tailed Mongoose (H. brachyurus) · Indian Gray Mongoose (H. edwardsii) · Indian Brown Mongoose (H. fuscus) · Egyptian Mongoose (H. ichneumon) · Small Asian Mongoose (H. javanicus) · Long-nosed Mongoose (H. naso) · Collared Mongoose (H. semitorquatus) · Ruddy Mongoose (H. smithii) · Crab-eating Mongoose (H. urva) · Stripe-necked Mongoose (H. vitticollis) Ichneumia White-tailed Mongoose (I. albicauda) Liberiictus Liberian Mongoose (L. kuhni) Mungos Gambian Mongoose (M. gambianus) · Banded Mongoose (M. mungo) Paracynictis Selous' Mongoose (P. selousi) Rhynchogale Meller's Mongoose (R. melleri) Suricata Meerkat (S. suricatta) Hyaenidae (Hyenas) Crocuta Spotted Hyena (C. crocuta) Hyaena Brown Hyena (H. brunnea) · Striped Hyena (H. hyaena) Proteles Aardwolf (P. cristatus) Felidae Large family listed below Viverridae Large family listed below Eupleridae Large family listed below   Family Felidae Felinae Acinonyx Cheetah (A. jubatus) Caracal Caracal (C. caracal) Catopuma Bay Cat (C. badia) · Asian Golden Cat (C. temminckii) Felis Chinese Mountain Cat (F. bieti) · Cat (F. catus) · Jungle Cat (F. chaus) · Pallas' Cat (F. manul) · Sand Cat (F. margarita) · Black-footed Cat (F. nigripes) · Wildcat (F. silvestris) Leopardus Pantanal Cat (L. braccatus) · Colocolo (L. colocolo) · Geoffroy's Cat (L. geoffroyi) · Kodkod (L. guigna) · Andean Mountain Cat (L. jacobitus) · Pampas Cat (L. pajeros) · Ocelot (L. pardalis) · Oncilla (L. tigrinus) · Margay (L. wiedii) Leptailurus Serval (L. serval) Lynx Canadian Lynx (L. canadensis) · Eurasian Lynx (L. lynx) · Iberian Lynx (L. pardinus) · Bobcat (L. rufus) Pardofelis Marbled Cat (P. marmorata) Prionailurus Leopard Cat (P. bengalensis) · Iriomote Cat (P. iriomotensis) · Flat-headed Cat (P. planiceps) · Rusty-spotted Cat (P. rubiginosus) · Fishing Cat (P. viverrinus) Profelis African Golden Cat (P. aurata) Puma Cougar (P. concolor) · Jaguarundi (P. yagouaroundi) Pantherinae Neofelis Clouded Leopard (N. nebulosa) · Bornean Clouded Leopard (N. diardi) Panthera Lion (P. leo) · Jaguar (P. onca) · Leopard (P. pardus) · Tiger (P. tigris) Uncia Snow Leopard (U. uncia)   Family Viverridae (includes Civets) Paradoxurinae Arctictis Binturong (A. binturong) Arctogalidia Small-toothed Palm Civet (A. trivirgata) Macrogalidia Sulawesi Palm Civet (M. musschenbroekii) Paguma Masked Palm Civet (P. larvata) Paradoxurus Asian Palm Civet (P. hermaphroditus) · Jerdon's Palm Civet (P. jerdoni) · Golden Palm Civet (P. zeylonensis) Hemigalinae Chrotogale Owston's Palm Civet (C. owstoni) Cynogale Otter Civet (C. bennettii) Diplogale Hose's Palm Civet (D. hosei) Hemigalus Banded Palm Civet (H. derbyanus) Prionodontinae (Asiatic linsangs) Prionodon Banded Linsang (P. linsang) · Spotted Linsang (P. pardicolor) Viverrinae Civettictis African Civet (C. civetta) Genetta (Genets) Abyssinian Genet (G. abyssinica) · Angolan Genet (G. angolensis) · Bourlon's Genet (G. bourloni) · Crested Servaline Genet (G. cristata) · Common Genet (G. genetta) · Johnston's Genet (G. johnstoni) · Rusty-spotted Genet (G. maculata) · Pardine Genet (G. pardina) · Aquatic Genet (G. piscivora) · King Genet (G. poensis) ·   Source: Wikipedia Unreviewed Article rating from 0 people Average rating: 2.5 of 5 Comment on or rate this article Disclaimer EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing. To request an improvement, please leave a comment on the page. Thank you!