Physical Description

Morphology

Other Physical Features: endothermic ; bilateral symmetry

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Ecology

Associations

Known prey organisms

Otariidae preys on:
Oncorhynchus tshawytscha

This list may not be complete but is based on published studies.
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Life History and Behavior

Behavior

Perception Channels: tactile ; chemical

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Reproduction

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records: 88
Specimens with Sequences: 68
Specimens with Barcodes: 34
Species: 13
Species With Barcodes: 13
Public Records: 58
Public Species: 13
Public BINs: 10
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Barcode data

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Wikipedia

Sea lion

This article is about the aquatic mammal. For other uses, see Sea lion (disambiguation).

Sea lions are sea mammals characterized by external ear flaps, long foreflippers, the ability to walk on all fours, and short, thick hair. Together with the fur seals they comprise the family Otariidae, eared seals, which contains six extant and one extinct species (the Japanese sea lion) 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.[1] They have an average life span of 20–30 years. A male California sea lion weighs on an average about 300 kg (660 lb) and is about 8 ft (2.4 m) long, while the female sea lion weighs 100 kg (220 lb) and is 6 ft (1.8 m) long. The largest sea lion is the Steller's sea lion which can weigh 1,000 kg (2,200 lb) and grow to a length of 10 ft (3.0 m). Sea lions consume large quantities of food at a time and are known to eat about 5–8% of their body weight (about 15–35 lb (6.8–15.9 kg)) at a single feeding.[citation needed]

The name sea lion is somewhat misleading as sea lions are only distantly related to lions and other felines. Sea lions evolved from the canines splitting from the bear line after it split form other dogs. Sea lions could thus more appropriately be called sea bears.

Taxonomy[edit]

Together with the fur seals, they constitute the Otariidae family, collectively known as eared seals. Until recently, sea lions were grouped under a single subfamily called Otariinae, whereas fur seals were grouped in the subfamily Arcocephalinae. This division was based on the most prominent common feature shared by the fur seals and absent in the sea lions, namely the dense underfur characteristic of the latter. Recent genetic evidence, however, strongly suggests Callorhinus, the genus of the northern fur seal, is more closely related to some sea lion species than to the other fur seal genus, Arctocephalus.[2] Therefore, the fur seal/sea lion subfamily distinction has been eliminated from many taxonomies. Sea lions are related to the walrus and the seal. 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. 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.

Interactions with humans[edit]

Some species of sea lion are readily trainable and are often a popular attraction at zoos and aquariums.

The U.S. Navy's Marine Mammal Program, based in San Diego, has trained sea lions to detain scuba divers.[3]

Sea lion attacks on humans are rare. In a highly unusual attack in 2007 in Western Australia, a sea lion leapt from the water and seriously mauled a 13-year-old girl surfing behind a speedboat. The sea lion appeared to be preparing for a second attack when the girl was rescued. An Australian marine biologist opined the sea lion may have viewed the girl "like a rag doll toy" to be played with.[4][5][6] In San Francisco, where an increasingly large population of California sea lion crowds dock along San Francisco Bay, there have been incidents in recent years of swimmers being bitten on the legs by large, aggressive males, possibly as territorial acts.[7][8][9]

The Moche people of ancient Peru worshipped the sea and its animals, and often depicted sea lions in their art.[10]

Images[edit]

Sea lions at Moss Landing, CaliforniaGiGi, a sea lion trained by the U.S. Navy for underwater recovery, nuzzles merchant mariner Capt. Arne Willehag of the USNS Sioux during a 1983 training session.Sea lion head.jpgSea Lion Lounging.JPGSea lion head by the ocean.jpg
A gathering of more than 40 sea lions off the coast of CaliforniaA military sea lion on board a U.S. Navy shipA sea lion at the Memphis ZooA sea lion pup sleeping at Pantai InnA sea lion in Malibu, California

See also[edit]

References[edit]

  1. ^ "California Sea Lion - SeaWorld Info Book". SeaWorld. Retrieved December 26, 2013. 
  2. ^ Wynen, L.P. et al.; Goldsworthy, SD; Insley, SJ; Adams, M; Bickham, JW; Francis, J; Gallo, JP; Hoelzel, AR et al. (2001). "Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family". Mol. Phylog. Evol. 21 (2): 270–284. doi:10.1006/mpev.2001.1012. PMID 11697921. 
  3. ^ Watkins, Thomas (2007-02-12). "Navy may deploy anti-terrorism dolphins". Associated Press. Retrieved 2007-02-12. 
  4. ^ BBC News: Sea lion attacks Australian girl
  5. ^ news.com.au: Monster sea lion likely to be 'playing' with teen
  6. ^ Sea lion mauls girl
  7. ^ Kay, Jane (2011-06-24). "Rogue sea lion in S.F. menaces swimmers / Marauding mammal bites at least 14, chases 10 from Aquatic Park Lagoon". The San Francisco Chronicle. 
  8. ^ [1][dead link]
  9. ^ Ashley Harrell (2009-10-07). "Too Cute to Shoot? - Page 1 - News - San Francisco". SF Weekly. Retrieved 2012-06-28. 
  10. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.


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Eared seal

Ear flaps of Otaria flavescens

An eared seal or 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 (another species became extinct in the 1950s) 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 and the southern Indian and Atlantic Oceans. They are conspicuously absent in the north Atlantic.

The words 'otariid' and 'otary' come from the Greek otarion meaning "little ear",[1] referring to the small but visible external ear flaps (pinnae), which distinguishes them from the phocids.

Evolution and taxonomy[edit]



Phocidae (true seals)



Otariidae





Antarctic fur seal




Guadalupe fur seal



Juan Fernández fur seal






Galápagos fur seal



southern fur seal






Australian sea lion



New Zealand sea lion





subantarctic fur seal



brown fur seal



South American sea lion








California sea lion



Galápagos sea lion




Japanese sea lion




Steller sea lion





northern fur seal



Odobenidae

 walrus




Cladogram showing the eared seals, Otariidae, and their relationships with other pinnipeds, combining several phylogenetic analyses.[2]

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.[3] Debate remains 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. The genus 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.[4] Recent analyses of the genetic evidence suggests that Callorhinus ursinus is in fact more closely related to several sea lion species.[5] 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.[6][7] 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, 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[edit]

Eared seal off the Namibian coast.

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 for eared seals is: 3.1.4.1-32.1.4.1. 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.

Male otariids range in size from the 70-kg (150-lb) Galápagos fur seal, smallest of all pinnipeds, to the over 1,000-kg (2,200-lb) Steller sea lion. 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 of all mammals.[8]

Behavior[edit]

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

Species[edit]

Family Otariidae

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.[9][10] 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.[11]

References[edit]

  1. ^ "Otary, n., etymology of" The Oxford English Dictionary. 2nd ed. 1989. OED Online. Oxford University Press. http://dictionary.oed.com/ Accessed November 2007
  2. ^ Berta, A.; Churchill, M. (2012). "Pinniped taxonomy: Review of currently recognized species and subspecies, and evidence used for their description". Mammal Review 42 (3): 207–34. doi:10.1111/j.1365-2907.2011.00193.x. 
  3. ^ Lento, G.M., Hickson, R.E., Chambers, G.K., Penny, D. (1 January 1995). "Use of spectral analysis to test hypotheses on the origin of pinnipeds". Molecular Biology and Evolution 12 (1): 28–52. doi:10.1093/oxfordjournals.molbev.a040189. PMID 7877495. 
  4. ^ J.E. King (1983). Seals of the World (2nd ed.). New York: Cornell University Press. ISBN 978-0-7022-1694-7. 
  5. ^ Wynen, L; Goldsworthy, SD; Insley, SJ; Adams, M; Bickham, JW; Francis, J; Gallo, JP; Hoelzel, AR et al. (2001). "Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family". Mol. Phylog. Evol. 21 (2): 270–284. doi:10.1006/mpev.2001.1012. PMID 11697921. 
  6. ^ Brunner, S. (2003). "Fur seals and sea lions (Otariidae): identification of species and taxonomic review". Systematics and Biodiversity 1 (3): 339–439. doi:10.1017/S147720000300121X. 
  7. ^ "Otariidae". Integrated Taxonomic Information System. Retrieved November 2007. 
  8. ^ Weckerly, FW (1998). "Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals.". Journal of Mammalogy 79 (1): 33–42. doi:10.2307/1382840. JSTOR 1382840. 
  9. ^ Yonezawa, T. et al. (2009). "The monophyletic origin of sea lions and fur seals (Carnivora; Otariidae) in the Southern Hemisphere". Gene 441 (1-2): 89–99. doi:10.1016/j.gene.2009.01.022. PMID 19254754. 
  10. ^ Arnason, U., et al. (2006). "Pinniped phylogeny and a new hypothesis for their origin and dispersal". Molecular Phylogenetics and Evolution 41 (2): 345–354. doi:10.1016/j.ympev.2006.05.022. PMID 16815048. 
  11. ^ Berta, A. & Churchill, M. (2012). "Pinniped Taxonomy: evidence for species and subspecies". Mammal Review 42 (3): 207–234. doi:10.1111/j.1365-2907.2011.00193.x. 

Further reading[edit]

  • 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.
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Fur seal

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.

Contents

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

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

See also

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.