An eared seal or otariid or otary is any member of the

marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their re ...

family Otariidae, one of three groupings of

pinnipeds Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the walru ...

. They comprise 15

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extin ...

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

in seven

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencl ...

(another species became extinct in the 1950s) and are commonly known either as

sea lion 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. ...

s or

fur seal 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 lo ...

s, distinct from

true seals 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 th ...

(phocids) and the

walrus The walrus (''Odobenus rosmarus'') is a large flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in the fami ...

( 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 The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

and

Southern Oceans The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

and the southern

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

and Atlantic Oceans. They are conspicuously absent in the north Atlantic. The words 'otariid' and 'otary' come from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

' meaning "little ear", referring to the small but visible external ear flaps (

pinnae The auricle or auricula is the visible part of the ear that is outside the head. It is also called the pinna (Latin for "wing" or "fin", plural pinnae), a term that is used more in zoology. Structure The diagram shows the shape and location of ...

), which distinguishes them from the phocids.

Evolution and taxonomy

Morphological and molecular evidence supports a monophyetic origin of pinnipeds, sharing a common ancestor with

Musteloidea Musteloidea is a superfamily of carnivoran mammals united by shared characters of the skull and teeth. Musteloids are the sister group of pinnipeds, the group which includes seals. The Musteloidea consists of the families Ailuridae (red pandas) ...

, though an earlier hypothesis suggested that Otаriidae are descended from a

common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ...

most closely related to modern

bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nort ...

s. Debate remains as to whether the phocids diverged from the otariids before or after the walrus. Otariids arose in the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

(15–17 million years ago) in the North Pacific, diversifying rapidly into the Southern Hemisphere, where most species now live. The earliest known fossil otariid is '' Eotaria crypta'' from southern California, while the genus ''Callorhinus'' (

northern fur seal The northern fur seal (''Callorhinus ursinus'') 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 th ...

) has the oldest fossil record of any living otariid, extending to the middle Pliocene. It probably arose from the extinct fur seal genus ''

Thalassoleon ''Thalassoleon'' ("sea lion" ) is an extinct genus of large fur seal. ''Thalassoleon'' inhabited the Northern Pacific Ocean in latest Miocene and early Pliocene. Fossils of ''T. mexicanus'' are known from Baja California and southern California. ...

''. 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. Recent analyses of the genetic evidence suggests that ''Callorhinus ursinus'' is in fact more closely related to several sea lion species. Furthermore, many of the Otariinae appear to be more

phylogenetically In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

distinct than previously assumed; for example, the

Japanese sea lion The Japanese sea lion (''Zalophus japonicus'') ( ja, ニホンアシカ, translit=Nihon ashika, Korean:강치, 바다사자) was an aquatic mammal that became extinct in the 1970s. It was considered to be a subspecies of the related California se ...

(''Zalophus japonicus'') is now considered a separate species, rather than a subspecies of the

California sea lion The California sea lion (''Zalophus californianus'') 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 Califo ...

(''Zalophus californius''). In light of this evidence, the subfamily separation has been removed entirely and the family Otariidae has been organized into seven genera with 16 species and two subspecies. Nonetheless, because of morphological and behavioral similarities among the "fur seals" and "sea lions", these remain useful categories when discussing differences between groups of species. Compared to sea lions, fur seals are generally smaller, exhibit greater

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most anim ...

, eat smaller prey and go on longer foraging trips; and, of course, there is the contrast between the coarse short sea lion hair and the fur seal's fur.

Anatomy and appearance

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 have 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 Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolog ...

for eared seals is: . Sea lions are covered with coarse guard hairs, while fur seals have a thick underfur, which has historically made them the objects of commercial

exploitation Exploitation may refer to: *Exploitation of natural resources *Exploitation of labour **Forced labour *Exploitation colonialism *Slavery **Sexual slavery and other forms *Oppression *Psychological manipulation In arts and entertainment * Exploit ...

. Male otariids range in size from the 70-kg (150-lb)

Galápagos fur seal The Galápagos fur seal (''Arctocephalus galapagoensis'') 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 Gal ...

, smallest of all otariids, to the over 1,000-kg (2,200-lb)

Steller sea lion The Steller sea lion (''Eumetopias jubatus''), also known as the Steller's sea lion and northern sea lion, is a near-threatened species of sea lion in the northern Pacific. It is the sole member of the genus ''Eumetopias'' and the largest of t ...

. Mature male otariids weigh two to six times as much as females, with proportionately larger heads, necks, and chests, making them the most

sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most anim ...

of all mammals.

Behavior

All otariids breed on land during well-defined breeding seasons. Except for the

Australian sea lion The Australian sea lion (''Neophoca cinerea''), 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 ...

, 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 Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women. Incidence Polygyny is more widespread in Africa than in any ...

; 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, no permanent hierarchies or statuses are 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 The South American sea lion (''Otaria flavescens'', formerly ''Otaria byronia''), 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 membe ...

tend to herd specific

harem Harem (Persian: حرمسرا ''haramsarā'', ar, حَرِيمٌ ''ḥarīm'', "a sacred inviolable place; harem; female members of the family") refers to domestic spaces that are reserved for the women of the house in a Muslim family. A hare ...

-associated females, occasionally injuring them, while the Steller sea lion and the

New Zealand sea lion The New Zealand sea lion (''Phocarctos hookeri''), once known as Hooker's sea lion, and as or (male) and (female) in Māori, is a species of sea lion that is endemic to New Zealand and primarily breeds on New Zealand's subantarctic Auckland a ...

control spatial territories, but do not generally interfere with the movement of the females. Female New Zealand sea lions are the only otrariids that move up to into forests to protect their pups during the breeding season. Otariids are carnivorous, feeding on

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

and

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish. Krill are cons ...

. Sea lions tend to feed closer to shore in

upwelling Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutr ...

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. Some females are capable of dives of up to 400 m (1,300 ft).

Species

Family Otariidae * Subfamily Arctocephalinae (fur seals) ** Genus '' Arctocephalus'' ***

Brown fur seal The brown fur seal (''Arctocephalus pusillus''), also known as the Cape fur seal, South African fur seal and Australian fur seal, is a species of fur seal. Description The brown fur seal is the largest and most robust member of the fur seals. ...

, ''A. pusillus'' ****South African fur seal, ''A. pusillus pusillus'' ****Australian fur seal, ''A. pusillus doriferus'' ***

Antarctic fur seal The Antarctic fur seal (''Arctocephalus gazella''), 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 ...

, ''A. gazella'' ***

Guadalupe fur seal The Guadalupe fur seal (''Arctocephalus townsendi'') is one of eight members of the fur seal genus '' Arctocephalus''. Sealers reduced the population to just a few dozen by the late 19th century, but the species had recovered to 10,000 in number ...

, ''A. townsendi'' ***

Juan Fernández fur seal The Juan Fernández fur seal (''Arctocephalus philippii'') 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 Isla ...

, ''A. philippii'' ***

, ''A. galapagoensis'' ***

New Zealand fur seal ''Arctocephalus forsteri'' (common names include the Australasian fur seal, South Australian fur seal, New Zealand fur seal, Antipodean fur seal, or long-nosed fur seal) is a species of fur seal found mainly around southern Australia and New Z ...

(or southern fur seal), ''A. forsteri'' ***

Subantarctic fur seal The subantarctic fur seal (''Arctocephalus tropicalis'') is 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 inappropri ...

, ''A. tropicalis'' ***

South American fur seal The South American fur seal (''Arctocephalus australis'') 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. Althou ...

, ''A. australis'' **Genus '' Callorhinus'' ***

Northern fur seal The northern fur seal (''Callorhinus ursinus'') 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 th ...

, ''C. ursinus'' * Subfamily Otariinae (sea lions) ** Genus ''

Eumetopias The Steller sea lion (''Eumetopias jubatus''), also known as the Steller's sea lion and northern sea lion, is a near-threatened species of sea lion in the northern Pacific. It is the sole member of the genus ''Eumetopias'' and the largest of t ...

'' ***

, ''E. jubatus'' ** Genus '' Neophoca'' ***

, ''N. cinerea'' ** Genus '' Otaria'' ***

, ''O. flavescens'' ** Genus '' Phocarctos'' ***

(or Hooker's sea lion), ''P. hookeri'' ** Genus '' Zalophus'' ***

, ''Z. californianus'' *** †

, ''Z. japonicus'' –

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

(1970s)''Zalophus californianus japonicus'' (CR)
Red Data Book, Japan Integrated Biodiversity Information System,

Ministry of the Environment (Japan) The is a Cabinet-level ministry of the government of Japan responsible for global environmental conservation, pollution control, and nature conservation. The ministry was formed in 2001 from the sub-cabinet level Environmental Agency establish ...

. "The Japanese sea lion (''Zalophus californianus japonicus'') was common in the past around the coast of the Japanese Archipelago, but declined rapidly after the 1930s from overhunting and increased competition with commercial fisheries. The last record in Japan was a juvenile, captured in 1974 off the coast of

Rebun Island is an island in the Sea of Japan off the northwestern tip of Hokkaidō, Japan. The island sits off the coast of Hokkaidō. Rebun stretches from north to south and from east to west. The island covers approximately . Rebun Island is located ...

, northern Hokkaido." ***

Galápagos sea lion The Galápagos sea lion (''Zalophus wollebaeki'') is a species of sea lion that lives and breeds on the Galápagos Islands and, in smaller numbers, on Isla de la Plata (Ecuador). Being fairly social, they are often spotted sun-bathing on sandy ...

, ''Z. wollebaeki'' Although the two subfamilies of otariids, the Otariinae (sea lions) and Arctocephalinae (fur seals), are still widely used, recent molecular studies have demonstrated that they may be invalid. Instead, they suggest three clades within the family; one consisting of the northern sea lions (''Eumetopias'' and ''Zalophus''), one of the northern fur seal (''Callorhinus'') and its extinct relatives, and the third of all the remaining Southern Hemisphere species.

References

External links