Northern fur seal
Northern fur seal | |||
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Scientific classification | |||
Domain: | Eukaryota | ||
Kingdom: | Animalia | ||
Phylum: | Chordata | ||
Class: | Mammalia | ||
Order: | Carnivora | ||
Clade: | Pinnipedia | ||
Family: | Otariidae | ||
Subfamily: | Arctocephalinae | ||
Genus: | Callorhinus | ||
Species: | C. ursinus
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Binomial name | |||
Callorhinus ursinus | |||
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Synonyms | |||
Phoca ursina Linnaeus, 1758 |
The northern fur seal (Callorhinus ursinus) is an
Description
Northern fur seals have extreme
Adult males are stocky in build, and have enlarged (thick and wide) necks. A mane of coarse, longer guard hairs extends from the lower neck to the shoulders.
Adult females, subadults, and juveniles are moderate in build. Distinguishing the sexes is difficult until about age five. The body is modest in size and the neck, chest, and shoulders are sized in proportion with the torso. Adult females and subadults have more complex and variable coloration than adult males. They are dark silver-gray to charcoal above. The flanks, chest, sides, and underside of the neck, often forming a chevron pattern in this area, are cream to tan with rusty tones. Variable cream to rust-colored areas are on the sides and top of the muzzle, chin, and as a "brush stroke" running backwards under the eye. In contrast, adult males are medium gray to black, or reddish to dark brown all over. Their manes can have variable amounts of silver-gray or yellowish tinting on the guard hairs. Pups are blackish at birth, with variable oval areas of buff on the sides, in the axillary area, and on the chin and sides of the muzzle. After three to four months, pups molt to the color of adult females and subadults.
Males can be as large as 2.1 m (6 ft 11 in) and 270 kg (600 lb). Females can be up to 1.5 m (4 ft 11 in) and weigh 50 kg (110 lb) or more. Newborns weigh 5.4–6 kg (12–13 lb), and are 60–65 cm (24–26 in) long.
The teeth are
Like other otariids, northern fur seals are built for efficient terrestrial locomotion. Their hind limbs are in a plantigrade stance and are able to rotate under the body for quadrupedal locomotion and support.[9] When swimming, there are two different types of movement: locomotion and diving. These seals swim primarily with forelimb propulsion due to their physiology. They have flexible joints between vertebrae for better maneuverability in the water as well as "greater muscular leverage" for pectoral strokes.[10] Stroke patterns are different for different dive types and locomotion, and stroke rates vary for individuals since there's a relationship between maximum stroke rate and body size.[11]
Distribution and habitat
The northern fur seal is found in the north Pacific – its southernmost reach is a line that runs roughly from the southern tip of
During the winter, northern fur seals display a net movement southward, with animals from Russian rookeries regularly entering Japanese and Korean waters in the Sea of Japan and Alaskan animals moving along the central and eastern Pacific to
The northern fur seal's range overlaps almost exactly with that of Steller sea lions; occasional cohabitation occurs at reproductive rookeries, notably in the Kurils, the Commander Islands, and Tyulen'i Islands. The only other fur seal found in the Northern Hemisphere is the Guadalupe fur seal which overlaps slightly with the northern fur seal's range in California.
Ecology
Fur seals are opportunistic feeders, primarily feeding on
Their feeding behavior is primarily solitary.Northern fur seals are preyed upon primarily by
Due to very high densities of pups on reproductive rookeries and the early age at which mothers begin their foraging trips, mortality can be relatively high. Consequently, pup carcasses are important in enriching the diet of many scavengers, in particular
In 2017, 14 samples of
Reproductive behavior
Seals enter breeding
After remaining with their pups for the first eight to ten days of their lives, females begin foraging trips lasting up to a week. These trips last for about four months before weaning, which happens abruptly, typically in October. Most of the animals on a rookery enter the water and disperse towards the end of November, typically migrating southward. Breeding site fidelity is generally high for fur seal females, though young males might disperse to other existing rookeries, or occasionally find new haulouts.[17]
Peak mating occurs somewhat later than peak birthing from late June to late July. As with many other otariids, the fertilized egg undergoes delayed implantation: after the blastocyst stage occurs, development halts and implantation occurs four months after fertilization. In total, gestation lasts around a year, such that the pups born in a given summer are the product of the previous year's breeding cycle.
Status
Recently, concern about the status of fur seal populations has increased, particularly in the Pribilof Islands, where pup production has decreased about 50% since the 1970s, with a continuing drop of about 6–7% per year. This has caused them to be listed as "vulnerable" on the
Fur trade
Northern fur seals have been a staple food of native northeast Asian and
Significant harvest was more or less arrested with the signing of the
See also
- Marine Mammal Center
References
- ^ . Retrieved 19 November 2021.
- ^ Linnæus, Carl (1758). Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I (in Latin) (10th ed.). Holmiæ: Laurentius Salvius. p. 37. Retrieved 23 November 2012.
- OCLC 62265494.
- .
- ^ ISBN 0-375-41141-0.
- ^ "Learn More About Northern Fur Seals". The Marine Mammal Center. Retrieved 7 May 2021.
- ^ "Northern Fur Seal (Callorhinus ursinus) Species Profile". State of Alaska · Department of Fish and Game. Retrieved 7 May 2021.
- JSTOR 1376230.
- ISBN 9780123735539.
- PMID 21668895.
- doi:10.3354/esr00050.
- ^ a b c d e Waerebeek, K. V., Wursi, B. "Northern Fur Sea Callorhinus ursinus" pp. 788–91 of Encyclopedia of Marine Mammals (edited by Perrin, W. F., Wursig, B and J. G.M. Thewissen), Academic Press; 2nd edition, (2008)
- ^ Ream, R.; Burkanov, V. (2005). "Trends in abundance of Steller sea lions and northern fur seals across the North Pacific Ocean" (PDF). Vladivostok, Russia: PICES XIV Annual Meeting.
- S2CID 109546688.
- .
- .
- ^ ISBN 0-691-03345-5
- ^ "North Pacific Fur Seal Treaty of 1911". National Oceanic and Atmospheric Administration.
- ^ Baker, R.C., F. Wilke, C.H. Baltzo, 1970. The northern fur seal, U.S. Dep. Int., Fish and Wildlife Service, Circ. 336, overall quote pp. 2–4, 14–17. Quoted on 4th p. of PDF, in "Fisheries Management: An Historical Overview" by Clinton E. Atkinson; p. 114 of Marine Fisheries Review 50(4) 1988.
Further reading
- Heptner, V. G.; Nasimovich, A. A; Bannikov, Andrei Grigorevich; Hoffmann, Robert S, Mammals of the Soviet Union, Volume II, part 3 (1996). Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation
External links
- ARKive - images and movies of the northern fur seal (Callorhinus ursinus)
- NOAA's National Marine Mammal Laboratory northern fur seal research program
- Georg Steller's original description of the "Sea Bear" in De Bestiis Marinis (1751)
- Smithsonian Institution - North American Mammals: Callorhinus ursinus