California sea lion
California sea lion Temporal range: Pleistocene– Recent[1]
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Male | |
Female Both in La Jolla, California
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Clade: | Pinnipedia |
Family: | Otariidae |
Genus: | Zalophus |
Species: | Z. californianus
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Binomial name | |
Zalophus californianus (
Lesson , 1828) | |
breeding range total range
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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 California. California sea lions are sexually dimorphic; males are larger than females, and have a thicker neck, and a protruding sagittal crest. They mainly haul-out on sandy or rocky beaches, but they also frequent manmade environments such as marinas and wharves. California sea lions feed on a number of species of fish and squid, and are preyed on by orcas and great white sharks.
California sea lions have a polygynous breeding pattern. From May to August, males establish territories and try to attract females with which to mate. Females are free to move in between territories, and are not coerced by males. Mothers nurse their pups in between foraging trips. California sea lions communicate with numerous vocalizations, notably with barks and mother-pup contact calls. Outside their breeding season, California sea lions spend much of their time at sea, but they come to shore to molt.
California sea lions are particularly
Taxonomy
The California sea lion was
Traditionally, the Galapagos sea lion and Japanese sea lion were classified as
Appearance, physiology, and movement
Being sexually dimorphic, California sea lions differ in size, shape, and coloration between the sexes. Males can grow up to 2.5–2.7 m (8.2–8.9 ft) long and weigh around 350 kg (770 lb), while females are typically around 2.1 m (6.9 ft) and weigh around 100 kg (220 lb).
As an otariid, the California sea lion relies on its foreflippers to propel itself when swimming. This form of aquatic locomotion, along with its streamlined body, effectively reduces drag underwater. Its foreflipper movement is not continuous; the animal glides in between each stroke.[11] The flexibility of its spine allows the California sea lion to bend its neck backwards far enough to reach its hindflippers. This allows the animal to make dorsal turns and maintain a streamlined posture.[12] When moving on land, the California sea lion is able to turn its hindflippers forward and walk on all fours. It moves the foreflippers in a transverse, rather than a sagittal, fashion. In addition, it relies on movements of its head and neck more than its hindflippers for terrestrial locomotion.[13] California sea lions may travel at speeds of around 10.8 km/h (6.7 mph),[14] and can dive at depths of 274 m (899 ft) and for up to 9.9 minutes, though most dives are typically 80 m (260 ft) and last less than 3 minutes.[15]
California sea lions have color vision, though it is limited to the blue-green area of the color spectrum. This is likely an adaptation for living in marine coastal habitats.[16] Sea lions have fairly acute underwater hearing, with a hearing range of 0.4–32 kHz.[17] California sea lions rely on their whiskers or vibrissae for touch and detection of vibrations underwater. Compared to the harbor seal, the California sea lion's vibrissae are smoother and less specialized and thus perform less when following hydrodynamic trails, although they still perform well.[18]
Ecology
Range and habitat
The California sea lion ranges along the western coast and islands of
Vagrants can reach the north-western Pacific such as on the Commander Islands.[19] Although several otariinae have been recorded around the Japanese archipelago in recent years, their exact origins are unclear.[20]
During the breeding season, California sea lions gather on both sandy and rocky shores. On warm days, they lie closer to the water. At night or in cool weather, they travel farther inland or to higher elevations.
Diet and predation
California sea lions feed on a wide variety of
California sea lions are preyed on by orcas and large sharks. At Monterey Bay, California sea lions appear to be the more common food items for transient mammal-eating orcas pods.[26] The California sea lions may respond to the dorsal fin of a killer whale and remain vigilant, even when encountering resident fish-eating pods.[27] California sea lions are also common prey for great white sharks. They have been found with scars made by attacks from both great white sharks and shortfin mako sharks. Sharks attack California sea lions by ambushing them while they are resting at the surface.[28] California sea lions that are attacked in the hindquarters are more likely to survive and make it to the shore.[29]
Life history
Reproductive behavior and parenting
California sea lions breed gregariously between May and August, when they arrive at their breeding
Before mating begins, females gather into "milling" groups of 2–20 individuals. The females in these groups will mount each other as well as the males. These groups begin to disintegrate as the females begin to mate.
Female California sea lions have a 12-month reproductive cycle, consisting of a 9-month actual gestation and a 3-month delayed implantation of the fertilized egg before giving birth in June or July. Interbirth intervals are particularly long for this species, being 21 days for sea lions off California and more than 30 days for sea lions in the Gulf of California.[32] Females remain with their pups onshore for 10 days and nurse them. After this, females will go on foraging trips lasting as long as three days, returning to nurse their pups for up to a day. Pups left onshore tend to gather in nurseries to socialize and play.[9] When returning from a trip, females call their pups with distinctive calls to which the pups will reply in kind. A mother and pup can distinguish each other's calls from those of other mothers and pups. At first, reunions largely depend on the efforts of the mothers. However, as pups get older, they get more involved in reunions.[33] Older pups may sometimes join their mothers during their foraging trips.[9] Adult male California sea lions play no role in raising pups, but they do take more interest in them than adult males of other otariid species; they have even been observed to help shield swimming pups from predators.[34] Pups are weaned by a year but can continue to suckle for another year.[4]
Communication
California sea lions communicate with a range of vocalizations. The most commonly used one is their characteristic
Female California sea lions are less vocal. Their barks, high-pitched and shorter than those made by males, are used in aggressive situations. Other aggressive vocalizations given by females include the "squeal", the "belch", and the "growl". The sound a female California sea lion gives when calling her pups is called a "pup-attraction call", described as "loud" and "brawling". Pups respond with a "mother-response call", which is similar in structure. Pups will also bleat or bark when playing or in distress.[35] California sea lions can produce vocalizations underwater. These include "whinny" sounds, barks, buzzings, and clicks.[36]
Nonbreeding activities
Outside the breeding season, males migrate to the northern ends of the species range to feed, while females forage near the breeding rookeries.[4] California sea lions can stay at sea for as long as two weeks at a time. They make continuous dives, returning to the surface to rest. California sea lions may travel alone or in groups while at sea and haul-out between each sea trip. Adult females and juveniles molt in autumn and winter; adult males molt in January and February. California sea lions in the Gulf of California do not migrate; they stay in the Gulf of California year-round.[32]
Intelligence and trainability
Marine biologist Ronald J. Schusterman and his research associates have studied the California sea lions' cognitive ability. They have discovered that California sea lions are able to recognize relationships between stimuli based on similar functions or connections made with their peers, rather than only the stimuli's common features.[37] California sea lions have demonstrated the ability to understand simple syntax and commands when taught an artificial sign language. However, California sea lions rarely used the signs semantically or logically.[38] In 2011, a California sea lion named Ronan was recorded bobbing her head in synchronization to musical rhythms.[39] This "rhythmic entrainment" was previously seen only in humans, parrots and other birds possessing vocal mimicry.[40]
Because of their intelligence and trainability, California sea lions have been used by circuses and marine mammal parks to perform various tricks such as throwing and catching balls on their noses, running up ladders, or honking horns in a musical fashion. Trainers reward their animals with fish, which motivates them to perform. For ball balancing, trainers toss a ball at a California sea lion so it may accidentally balance it or hold the ball on its nose, thereby gaining an understanding of what to do. A California sea lion may go through a year of training before performing a behavior for the public. However, its memory allows it to perform a behavior even after three months of resting.[34] Some organizations, such as the Humane Society of the United States and World Animal Protection, object to using California sea lions and other marine mammals for entertainment, claiming the tricks are "exaggerated variations of their natural behaviors" and distract the audience from the animal's unnatural environment.[41]
The California sea lion is used in
Status
The
In the United States, the California sea lion is protected on the federal
These animals exploit more human-made environments like docks for haul-out sites. Many docks are not designed to withstand the weight of several resting California sea lions which cause major tilting and other problems. Wildlife managers have used various methods to control the animals and some city officials have redesigned docks so they can better withstand them.[51][52]
2015 Californian shore sea lions pups crisis
In January and February 2015, 1450 malnourished or sick California sea lion pups were found along stretches of the California coast, and estimations give a higher number of dead pups. The
Oregon and Washington state governments annual killings
In November 2018, the State of Oregon obtained a permit to kill 93 California sea lions per year below Willamette Falls. Under a similar program, Oregon and Washington had killed over 150 California sea lions on the Columbia River by January 2019. In both cases, the purpose was to protect the local populations of fish (such as trout or salmon) from predation by the sea lions.
References
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- ^ . Retrieved 11 November 2021.
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- ^ a b Lowry, M.S.; Carretta, J.V. (1999). "Market squid (Loligo opalescens) in the diet of California sea lions (Zalophus californianus) in southern California (1981–1995)" (PDF). Reports of California Cooperative Oceanic Fisheries Investigations. 40: 196–207. Archived from the original (PDF) on 2013-04-12.
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- doi:10.1111/j.1748-7692.2011.00473.x. Archived from the original(PDF) on 2013-05-13. Retrieved 2012-06-08.
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- ^ Commander Islands Nature and Biosphere Reserve. California sea lion Zalophus californianus Lesson, 1828. Retrieved on August 24, 2017
- ^ 鹿児島県薩摩川内市で種不明アシカ出現 Archived 2016-06-02 at archive.today- 海棲哺乳類情報データベース
- ^ "Columbia River Sea Lion Management: Restoring balance between predators and salmon". Washington Department of Fish & Wildlife. Archived from the original on 21 October 2017. Retrieved 23 May 2012.
- ^ Kay, Jane (10 February 2012). "When good fishing trips go bad: Sea lion swims the Delta – lands on Merced County farm road". San Francisco Chronicle. Retrieved 3 July 2012.
- ^ "Sea Lion Diet". Southwest Fisheries Science Center. Retrieved 2 September 2007.
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- ^ Ternullo, Richard; Black, Nancy. "Predation Behavior of Transient Killer Whales in Monterey Bay, California". Monterey Bay Whale Watch. Retrieved 23 May 2012.
- ^ Baird, Robin W.; Stacey, Pam J. (1989). "Observations on the reactions of sea lions, Zalophus californianus and Eumetopias jubatus, to killer whales, Orcinus orca; evidence of "prey" having a "search image" for predators" (PDF). Canadian Field-Naturalist. 103 (3): 426–428. Retrieved 23 May 2012.
- ^ Harris, Jeffrey D.; Melin, Sharon R.; DeLong, Robert L. "Shark-inflicted Lesions on California Sea Lions (Zalophus californianus) at San Miguel Island, California: a New Phenomenon" (PDF). National Marine Mammal Laboratory – Alaska Fisheries Science Center. Archived from the original (PDF) on 12 July 2012. Retrieved 23 May 2012.
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- ^ Stephens, Tim (1 April 2013). "Sea lion defies theory and keeps the beat". University of California, Santa Cruz. Retrieved 12 April 2013.
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- ^ "The Case Against Marine Mammals in Captivity" (PDF). Humane Society of the United States and World Animal Protection. p. 3. Archived from the original (PDF) on 30 September 2018. Retrieved 30 May 2012.
- ^ Leinwand, Donna (17 February 2003). "Sea lions called to duty in Persian Gulf". USA Today. Retrieved 28 April 2010.
- ^ Kreider, R. (May 31, 2011). "The Real Navy Seals – and Sea Lions and Dolphins and Whales". ABC News. Retrieved July 30, 2013.
- ^ "Frequently Asked Questions". U.S. Navy Marine Mammal Program. Archived from the original on June 19, 2013. Retrieved July 30, 2013.
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- ^ "NOAA authorizes states to remove California sea lions that threaten protected salmon" (PDF). National Oceanic and Atmospheric Administration. Archived from the original (PDF) on 22 October 2013. Retrieved 17 October 2013.
- KATU. Archived from the originalon 10 May 2013. Retrieved 9 June 2012.
- ^ "Columbia River Sea Lion Management: Restoring balance between predators and salmon". Washington State Department of Fish & Wildlife. Archived from the original on 21 October 2017. Retrieved 23 May 2012.
- The Humane Society of the United States. Archived from the originalon 18 October 2013. Retrieved 17 October 2013.
- ^ French, C. (April 10, 2013). "Sea Lions Take Over Ventura Docks". the Log.com. Retrieved August 17, 2013.
- ^ Bruscas, A. (July 27, 2012). "Shocking new idea for sea lion control". The Daily World.com. Archived from the original on September 21, 2013. Retrieved August 17, 2013.
- ^ Hecht, Peter (2015-03-07). "Sick, starving sea lion pups wash up in record numbers on California coast". The Sacramento Bee. Retrieved 12 March 2015.
- ^ "More Than 100 Sick Sea Lion Flooded On California Coastline". Retrieved 12 March 2015.
- ^ "Mass Death of Seabirds in Western U.S. Is 'Unprecedented'". news.nationalgeographic.com/. 2015-01-24. Archived from the original on January 26, 2015. Retrieved 12 March 2015.
- ^ GILLIAN FLACCUS (10 January 2019). "Oregon begins killing sea lions after relocation fails". Associated Press. Retrieved 10 January 2019.
In a similar program, Oregon and Washington have already killed more than 150 sea lions below the Bonneville Dam on the Columbia River to protect threatened and endangered salmon.
- ^ "California Sea Lion Management: Restoring balance between predators and salmon". Oregon Department of Fish and Wildlife. Archived from the original on 17 October 2013. Retrieved 17 October 2013.
- ^ "U.S. allows killing sea lions eating at-risk Northwest salmon". kgw.com. August 14, 2020. Retrieved 2023-11-05.
- ^ "Battle over endangered fish has led Oregon to cull sea lions". kgw.com. April 11, 2023. Retrieved 2023-11-05.
External links
- Media related to Zalophus californianus at Wikimedia Commons
- WDFW Fact Sheet on sea lions
- USACE information on sea lion deterrents
- Smithsonian Institution – North American Mammals: Zalophus californianus
- Voices in the Sea - Sounds of the California Sea Lion Archived 2014-07-09 at the Wayback Machine
- Photos of California sea lion on Sealife Collection