Steller sea lion
Steller sea lion Temporal range:
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Adult male, female and pup on Yamsky Islands in the northeast Sea of Okhotsk
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Size of male (left) and female (middle) compared to a 1.75-metre (5 ft 9 in) human
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Clade: | Pinnipedia |
Family: | Otariidae |
Genus: | Eumetopias Gill , 1866
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Species: | E. jubatus
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Binomial name | |
Eumetopias jubatus (Schreber, 1776)
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Range of Steller sea lions (purple = overall range, red = breeding rookeries) |
The Steller sea lion (Eumetopias jubatus, also known as Steller's sea lion or the northern sea lion) is a large,
Description
Adult animals are lighter in color than most sea lions, ranging from pale yellow to tawny and occasionally reddish. Steller sea lion pups are born almost black, weighing around 23 kg (51 lb), and remain dark in coloration for several months. Females and males both grow rapidly until the fifth year, after which female growth slows considerably. Adult females measure 2.3–2.9 m (7.5–9.5 ft) in length, on average being 2.5 m (8.2 ft), and weigh 240–350 kg (530–770 lb), with an average of 263 kg (580 lb).[3][4] Males continue to grow until their secondary sexual traits appear in their fifth to eighth year. Males are slightly longer than the females, growing to about 2.82–3.25 m (9.3–10.7 ft) long and averaging 3 m (9.8 ft) in length.[5] Males have much wider chests, necks, and general forebody structure. Males can weigh between 450–1,120 kg (990–2,470 lb), weighing on average 544 kg (1,199 lb).[6][7][8] Males are further distinguished from females by broader and higher foreheads, flatter snouts, and a thick mane of coarse hair[9] around their large necks. Their Latin name translates roughly as "maned one with the broad forehead".
Range
The
In the summer, Steller sea lions tend to shift their range somewhat southward. Therefore, though there are no reproductive rookeries in Japan, several consistent
Ecology
Habitat
Steller sea lions tend to live in the coastal waters of the
Foraging
Steller sea lions are skilled and
The composition of the diet of Steller sea lions varies seasonally and geographically; as opportunistic predators, they concentrate on the locally most abundant prey species.
Predation
Steller sea lions are top-tier carnivores, but are susceptible to predation, primarily by
Behavior and life history
Reproduction
Reproductively mature male sea lions gather together mid-spring on traditional, well-defined reproductive
Pregnant females give birth soon after arriving on a rookery, and copulation generally occurs one to two weeks after giving birth,[23][24] but the fertilized egg does not become implanted in the uterus until the fall. A fertilized egg may remain in embryonic diapause for up to three months before implanting and beginning to divide.[26] Twins are rare.[27] After a week or so of nursing without leaving the rookery, females begin to take progressively longer and more frequent foraging trips leaving their pups behind until at some point in late summer, when both the mother and pup leave the rookery together. This maternal attendance pattern is common in otariids. As pups get older the amount of time spent by females foraging out at sea increases. This continues until pups obtain the ideal body weight and energy reserves to eat on their own. A study conducted by the University of California, Santa Cruz found that on average male pups consume more milk than females. This may be due to the sexual dimorphism common to otariids.[28] Reproductive males fast throughout the reproductive season,[29] often without entering the water once from mid-May until August, when the structure of the reproductive rookeries begins to fall apart and most animals leave for the open seas and disperse throughout their range.
The age at weaning is highly variable; pups may remain with their mothers for as long as four years. Incidents of mothers feeding daughters that are simultaneously feeding their own newborn pups have been documented, which is an extremely rare occurrence among mammals. A study done at Año Nuevo in 1983 found that female attendance and time spent with their pup was shaped by increasing nutritional demands of the pup and the pups suckling efficiency. Females averaged 21 hours ashore and 36 hours at sea. As the pups aged, females began to spend more time at sea again. As the pups matured, specifically at the sixth week past birth, the mother's sea time declined by 30 percent. There was no relationship between the pups' activity or physical excursion and their suckling time, age, or sex. Their suckling time, and age, and sex are unrelated to their use of energy. Labeled water studies showed that the pups' milk intake had a direct relationship to their size. Pups that consumed more milk were heavier than those that did not. These findings show that the amount of time females spend onshore with their pups is based on their pup's suckling efficiency and nutritional demands.[30]
In the past, the low pup production has been tied to an increase in nutritional stress found in females. This was believed to have contributed to the decline in Steller sea lions common to Alaska.[26]
Locomotion
The largest of the eared seals, Steller sea lions are quick swimmers, about as fast as the smaller California sea lions. Glide velocity of individual Steller sea lions has been measured as 2.9–3.4 meters or 1.2–1.5 body lengths per second, which is close to the optimal swim velocity of 1.4 body lengths per second based on the minimum cost of transport for California sea lions.[31]
A 2007 study of Steller sea lions found that a majority of thrust was produced during the
Diving
To be able to dive for a long period of time, Steller sea lions exhibit apnea, bradycardia, and peripheral vasoconstriction. This allows them to maximize their oxygen stores and efficiently forage during their dives. In addition to those adaptations, their thick blubber layer and outer fur layer keep their body insulated during dives.[33]
Trained Steller sea lions from Vancouver Aquarium were placed in the open ocean at the University of British Columbia's Open Water Research Station to study their diving metabolism and behavior.[34] Steller sea lions' dives are more energetically costly if they perform dive bouts. The aerobic diving limit of Steller sea lions was observed to be affected by their nutritional state and feeding.[35]
Communication
Like most otariids, Steller sea lions are vocal in air. Mature male sea lions have a range of vocalizations as part of their territorial behaviors, including belches, growls, snorts, and hisses that serve as warnings to others. Both males and females also produce underwater noises similar to their above water sounds, described as clicks, barks, and belches.[36] The primary function of their vocalizations is for social behavior. Sonogram readings reported that Steller Sea Lions make discrete, low frequency pulses underwater that resemble the male "belching" territorial noise made in air. These underwater vocalizations have an average of 20–30 pulses per second.[37]
Vocalizations are critical to mother-pup pairs, as the mothers must find their pups in a crowded breeding area when they return from foraging. The mother and pup both use distinctive calls, like names, to help differentiate themselves among the crowd of other sea lions.[38] Their aerial vocalizations have been described as similar to the bleats of sheep, and bellows.
Because Steller sea lions are sexually dimorphic in size, their hearing differs in sensitivity, possibly due to differences in size of the hearing structures. Females have a higher sensitivity than males, perhaps to hear the higher frequency calls of their pups. The Steller sea lion's hearing range also suggests that they are capable of hearing the underwater calls of one of their main predators, the killer whale.[39]
Interactions with humans
Steller sea lion were hunted for meat and other commodities by prehistoric communities everywhere their range intersected with human communities. Aside from food and clothing, their skin was used to cover
Historically, the sea lion has had only very slight commercial value. For example, in the 19th century their
Steller sea lions are sometimes killed intentionally by fishermen, as they are seen as competitors and a threat to fish stocks.[1] Killing sea lions is strictly prohibited in the US and Russia; however, in Japan, a fixed number are still harvested annually, ostensibly to protect their fisheries. In Canada, commercial hunting is prohibited, but limited hunting permits are occasionally granted for First Nations communities, or if local culling is deemed necessary, for example, nuisance animals destroying fish farms.[citation needed]
In recent years, Steller sea lions have been known to enter the
Recent decline and subsequent recovery
While the populations of the eastern and Asian stocks appear stable, the population of the western stock, particularly along the
One suspected cause of their precipitous decline was the overfishing of
Another possible reason for decline in this species has been tied to the nutritional stress hypothesis. The lack of prey corresponds to the decrease in population. In females specifically, obtaining an insufficient amount of nutrients has resulted in the failure to complete their pregnancies to full term.[50]
In October 2013, the eastern Steller sea lion was taken off the U.S. Endangered Species List after a major population comeback over the past several years.[51]
See also
References
- ^ . Retrieved 19 November 2021.
- ^ "NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 11 October 2022.
- ^ Steller Sea Lions, Eumetopias jubatus. marinebio.org
- ^ Steller Sea Lions Archived 19 March 2012 at the Wayback Machine. Northwest Regional Office. noaa.gov
- JSTOR 3503908. Archived from the original(PDF) on 3 March 2016. Retrieved 27 October 2012.
- ISBN 978-0-7894-7764-4.
- ^ Keranen, Danielle. Eumetopias jubatus. Steller sea lion. Animal Diversity Web
- ^ Olesiuk, Peter F, and Bigg, Michael A. (~1984) Marine mammals in British Columbia.
- ^ "Steller Sea Lion (Eumetopias jubatus)". NOAA Fisheries. Retrieved 21 May 2017.
- ^ Alaska Marine Mammal Stock Assessments, 2009. (PDF) . Retrieved on 16 September 2011.
- ^ Allen, B. M., and R. P. Angliss (revised 25 November 2008) NOAA-TM-AFSC-206. STELLER SEA LION (Eumetopias jubatus): Eastern U. S. Stock. (PDF).
- ^ "Steller Sea Lion (Eumetopias jubatus)" Seal Conservation Society Accessed 25 April 2013
- PMID 32913674.
- ^ Fisheries, NOAA (29 May 2018). "Steller Sea Lion | NOAA Fisheries". www.fisheries.noaa.gov. Retrieved 7 June 2018.
- ^ ISBN 9780123735539
- ISSN 0718-1957.
- ^ JSTOR 3801420.
- ^ JSTOR 1383503.
- ^ a b c Keyes, M. C. (1968). "The nutrition of pinnipeds", pp. 359–395 in R. J. Harrison, R. C. Hubbard, R. S. Peterson, C. E. Rice, and R. J. Schusterman (eds.) The behavior and physiology of pinnipeds. Appleton, Century-Crofts, New York.
- ^ JSTOR 1376909.
- ^ JSTOR 1378115.
- ^ "Alaska | NOAA Fisheries" (PDF). 7 September 2021.
- ^ a b Gentry, R. L. (1970). "Social Behavior of the Steller’s Sea Lion". PhD Thesis, University of California, Santa Cruz, CA.
- ^ a b Sandergen, F. E. (1970). 'Breeding and Maternal Behavior of the Steller's Sea Lion (Eumetopias jubatus) in Alaska', M. S. Thesis, University of Alaska, College.
- ^ "Cannibal Sea Lion Kills and Eats Pup—Never Before Seen". nationalgeographic.com. 16 August 2017. Archived from the original on 16 August 2017.
- ^ doi:10.1139/z98-149.
- ^ Alaska Department of Fish and Game, "Life History". Adfg.alaska.gov. Retrieved on 17 December 2011.
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- ^ Haynes, Terry L. and Mishler, Craig (1991) The subsistence harvest and use of Steller sea lions in Alaska. Technical paper no. 198. Alaska Dept. of Fish and Game, Division of Subsistence. Juneau, Alaska
- .
- NOAA, March 2008, archived from the original(PDF) on 23 July 2012, retrieved 16 April 2012
- ^ Steller Sea Lion. US National Marine Fisheries Service .
- ^ Steller sea lion (Eumetopias jubatus). U.S. Fish & Wildlife Service.
- ^ Biodiversity: Pity the copepod. The Economist (16 June 2012). Retrieved on 27 October 2012.
- PMID 22272296.
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- ^ "Sea Lion Species Removed from Endangered Species List". Yahoo News. Retrieved 27 October 2013.
Further reading
- Heptner, V. G.; Nasimovich, A. A; Bannikov, Andrei Grigorevich; Hoffmann, Robert S (1988). Mammals of the Soviet Union. Vol. II, part 3. Washington, D.C.: Smithsonian Institution Libraries and National Science Foundation.
External links
- Marine Mammal Center – Steller Sea Lion
- US National Marine Fisheries Service Steller Sea Lion web page
- ARKive – images and movies of the Steller sea lion (Eumetopias jubatus)
- Alaska Department of Fish and Game page on Steller sea lions
- Overview of Steller sea lion research at NOAA, National Marine Fisheries Service, National Marine Mammal Lab
- Nature documentary about the decline of Steller's sea lions Archived 17 June 2008 at the Wayback Machine
- News media report on Steller sea lions and sturgeon interactions Archived 3 March 2016 at the Wayback Machine
- SeaLionPredation.com – news and information on seal and sea lion predation of salmon and steelhead in the Pacific Northwest
- NOAA fact sheet on pinnipeds in the Columbia River
- Georg Steller's original description in De Bestiis Marinis, or, The Beasts of the Sea (1751)
- Steller sea lion (Eumetopias jubatus) video clips from the BBC archive on Wildlife Finder
- Fifteen years of research into the Alaska populations of Steller Sea Lions at the Alaska SeaLife Center
- Video: Sea lions ward off attacking orcas