http___en.wikipedia.org_wiki_California_sea_lion.xml
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Калифорнийски морски лъв Калифорнийският морски лъв (Zalophus californianus) е ушат тюлен, разпространен по Северноамериканското крайбрежие на Тихия океан. С високия си интелект, адаптивност към успешно съжителство с човекa и лесно поддаване на дресировка, именно този морски лъв е тюленът, който сме свикнали да виждаме в зоопаркове, циркове и аквариуми. Добре обучени калифорнийски морски лъвове се използват дори в морски операции на Американската армия. Съдържание Физическа характеристика[редактиране | редактиране на кода] Мъжките достигат до 2,4 метра дължина на тялото и тежат до 300 kg, а женските са значително по-дребни и рядко надхвърлят 90 kg. Когато достигнат полова зрялост мъжките се сдобиват с костен гребен отгоре на черепа, откъдето идва научното наименование на вида, от латински: loph — чело, а представката za- служи за емфаза, т.е. Zalophus californianus означава Калифорнийско високочело. Полово активните мъжки, или т.нар. секачи имат също така дебел врат и своеобразна къса грива. Малките се раждат тъмнокафяви и тежат около 7 kg. Когато станат на 4-5 месеца, те сменят козината си с по-светлокафява до сребриста. Женските и младите мъжки са по-светли от възрастните мъжкари. Когато козината им е суха, окраската им е шоколадово кафява до червеникава. Разпространение[редактиране | редактиране на кода] Както говори наименованието му, Калифорнийският морски лъв се среща главно по бреговете на Калифорния (САЩ) и Калифорнийския залив (Мексико), като обикновено не навлиза на повече от 20 km навътре в океана. Предпочитани места за размножаване са пясъчните плажове на островите Сан Мигел и Сан Николас. След размножителния сезон мъжките мигрират на север до Британска Колумбия. Тогава могат да се видят струпани по вълноломи, кейове и светещ буй навигационни буйове. Тези конструкции и човешкото присъствие въобще им осигуряват защита от естествените им врагове: косатки и бели акули. Сродни видове[редактиране | редактиране на кода] Доскоро Галапагоските морски лъвове (Zalophus wollebaeki) и изчезналите през 50-те години на 20 век Японски морски лъвове (Zalophus japonicus) бяха считани за изолирани популации Калифорнийски морски лъвове и някои учени продължават да твърдят, че става въпрос за един и същ вид с 3 локални подвида.[2] Начин на живот и хранене[редактиране | редактиране на кода] Калифорнийските морски лъвове се хранят с най-разнообразна морска храна, основно с главоноги (сепии, октоподи) и риба (сьомга, хек, херинга, аншоа и др.). Ловуват самостоятелно или на малки групи, но при наличие на големи рибни пасажи се събират на големи стада и ловуват съвместно с други морски животни, като делфини, морски свине, морски птици и др. През зимната миграция на север мъжките се събират в устията на реки очаквайки миграцията на сьомга и есетрови риби. Най-добре се гмуркат възрастните женски. Навлизайки от 10 до 100 km навътре в океана, те се гмуркат на средна дълбочина от 30 до 100 m, а максималната регистрирана дълбочина на гмуркане е 274 m. Морските лъвове са изразено социални и общителни животни. Най-често издават звуци подобни на кучешки лай. Женските могат да открият своето малко сред хиляди изглеждащи по един и същи начин, разпознавайки го по гласа, звуците които издава и уникалната му миризма. Нормалната телесна температура на калифорнийския морски лъв е 37,5°C и след като няма нито потни жлези, нито се задъхва като кучетата, за да не прегрее в горещи дни се налага често да влиза във водата. Размножаване[редактиране | редактиране на кода] Размножителният период на калифорнийските морски лъвове продължава от май до юни. Те са изразено полигамни животни — мъжките образуват хареми, като излизайки на брега най-силните заемат най-добрите места, запазвайки си правото над женските на своя територия. За да отстояват територията си обаче, необходимо е те да останат колкото се може по-дълго на брега, разчитайки изцяло на натрупаните си хранителните запаси под формата на подкожни мазнини. Така мъжките могат да издържат до 27 дни на глад и горещини, но след като излязат на брега, женските раждат малките си и се разгонват не по-рано от 21-ия ден след раждането. Затова мъжките се активизират и стават много агресивни малко след раждането на малките. Тогава битките за територия и женските в нея стават много ожесточени, като съперниците не само си причиняват сериозни наранявания, но и безогледно мачкат всичко по пътя си представлявайки сериозна заплаха за малките. С напредването на лятото страстите се утоляват и мъжките престават да се бият, заплашвайки се само с лай, поклащане на глава, погледи и посягания. След 12-месечна бременност женските раждат по едно малко. Женската кърми малкото си 1-2 дни, след което го оставя само на брега за 2-3 дни, за да се нахрани в морето. Това продължава около два месеца, след което малкото влиза във водата и остава с майка си близо година. Малките се раждат с отворени очи и бозаят до шест месечна възраст нараствайки неимоверно благодарение на високата масленост на майчиното мляко. Калифорнийският морски лъв е единствения бозайник, чието мляко не съдържа лактоза. Полова зрялост достигат на 4-5 годишна възраст. Природозащитен статус[редактиране | редактиране на кода] Безмилостно избивани в миналото заради кожата, за храна на животни или просто защото се смята, че сериозно вредят на рибните запаси, калифорнийските морски лъвове са били застрашени от изчезване. Благодарение на взетите защитни мерки обаче, днес популацията на вида надхвърля 200 000 екземпляра и той фигурира в Червения списък на световнозастрашените видове на IUCN като незастрашен[3]. Допълнителни сведения[редактиране | редактиране на кода] През 1970 г. сред калифорнийските морски лъвове се разпространява заразната болест лептоспироза, засягаща черния дроб и бъбреците. Болестта е първият известен случай на широкоразпространена зараза сред морски животни. Вероятно болестта е тръгнала от Мексико поради по-топлата вода, която предразполага към развитие и разпространение на бактерии. Продължителност на живота[редактиране | редактиране на кода] В природата калифорнийските морски лъвове рядко доживяват 17 години, но най-възрастният индивид в плен доживял 31-годишна възраст. Стопанско значение[редактиране | редактиране на кода] В миналото калифорнийските морски лъвове са били избивани заради своята кожа и за храна на животни, в резултат на което броят им драстично е намалял. Днес обаче са защитени и нямат стопанско значение. Външни препратки[редактиране | редактиране на кода] Бележки[редактиране | редактиране на кода] - ↑ ((en)) Aurioles, D. & Trillmich, F.. Zalophus californianus. // IUCN Red List of Threatened Species. Version. International Union for Conservation of Nature, 2008. Посетен на 30 January 2009. - ↑ Don E. Wilson & DeeAnn M. Reeder (editors). 2005. Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed), Johns Hopkins University Press, 2,142 pp. Online - ↑ Zalophus californianus (IUCN Red List of Threatened Species, 2007)
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California sea lion The California sea lion (Zalophus californianus) is a coastal sea lion of western North America. Their numbers are abundant (188,000 U.S. stock, 1995 estimate),[2] and the population continues to expand about 5% annually.[3] They are quite intelligent and can adapt to man-made environments. Because of this, California sea lions are commonly found in public displays in zoos and marine parks and trained by the U.S. Navy for certain military operations. The California sea lion is the classic "circus seal," although it is not a true seal.[4] [edit] Description California sea lion males grow to 360 kg (850 lbs) and 2.4 meters (8 ft) long, while females are significantly smaller, at 100 kg (220 lbs) and 2 m (6.5 ft) long. They have pointed muzzles, making them rather dog-like. Males grow a large crest of bone on the top of their heads as they reach sexual maturity, and this gives the animal its generic name (loph is "forehead" and za- is an emphatic; Zalophus californianus means "Californian big-head"). They also have manes, although they are not as well developed as the manes of adult male South American or Steller sea lions. Females are lighter in color than the males, and pups are born dark, but lighten when they are several months old. When it is dry, the skin is a purple color. A sea lion's average lifespan is 17 years in the wild, and longer in captivity. By sealing their noses shut, they are able to stay underwater for up to 20 minutes.[5] [edit] Ecology [edit] Range and populations As its name suggests, the California sea lion is found mainly around the waters of California. However, they can also be found from the Alaska Panhandle in the north to Mexico in the south. The Galápagos sea lion and the extinct Japanese sea lion were once considered subspecies of the Californian sea lion. Now, these two populations are generally considered as distinct species.[6] The California sea lion population is divided into three stocks.[7] The U.S. stock ranges from waters around the Mexico–United States border to Southeast Alaska. It breeds mainly at the Channel Islands. The sea lions apparently have taken up breeding sites in northern California, and females are now commonly found there.[1] The western Baja California stock ranges from the waters around the U.S.-Mexico border to the southern tip of the Baja California peninsula. This stock breeds mainly at the Cedros Island area and near Puerto San Carlos. The Gulf of California stock is found throughout the Gulf of California and breeds mainly in the Isla Ángel de la Guarda/Tiburón Island region. [edit] Habitat California sea lions prefer to breed on sandy beaches. They usually stay no more than 10 miles out to sea.[8] On warm days, they stay close to the water's edge. At night or on cool days, the sea lions will move inland or up coastal slopes. Outside of the breeding season, they will often gather at marinas and wharves, and may even be seen on navigational buoys. Sea lions living around islands are less vulnerable to predation than coastal ones.[9] The sea lion's major predators are killer whales and white sharks.[9] California sea lions can also live in fresh water for periods of time. They feed on Pacific salmon in front of Bonneville Dam, 146.1 river miles from the Pacific Ocean. Historically, sea lions hunted salmon in the Columbia River as far as The Dalles and Celilo Falls, 200 miles (320 km) from the sea, as remarked upon by people such as George Simpson in 1841[citation needed]. In 2004, a healthy sea lion was found sitting on a road in Merced County, California, almost a hundred miles upstream from San Francisco Bay and half a mile from the San Joaquin River.[10] [edit] Diet California sea lions feed on a wide variety of seafood, mainly squid and fish, and sometimes even clams. Commonly eaten fish and squid species include salmon, hake, Pacific whiting, anchovies, herring, schooling fish, rock fish, lampreys, dog fish, and market squid.[11] They feed mostly around the edge of the continental shelf sea mounts, the open ocean and the ocean bottom. Average annual food consumption of males in zoos increases with age to stabilize at approximately 4,000 kg (8,818 lbs)/year by the age of 10 years. Females showed a rapid increase in average annual food consumption until they were three years old. Thereafter, females housed outdoors averaged 1,800 kg (3,968 lbs)/year.[12] California sea lions may eat alone or in small to large groups, depending on the amount of food available. They will cooperate with other predators (dolphins, porpoises, and seabirds) when hunting large schools of fish.[13] Sea lions in Washington will wait at the mouths of rivers for the salmon run. They also have learned to feed on steelhead and white sturgeon below fish ladders at Bonneville Dam and at other locations in the Columbia River, Willamette River, and in Puget Sound.[14] Adult females forage between 10 and 3000 km from the rookery, and dive to average depths of 31.1 to 98.2 m, with maximum dives between 196 and 274 m. They travel at an estimated speed of 10.8 km/h, and young sea lions have an initial defecation time averaging 4.2 hours. Adult females spend 1.6-1.9 days on land and 1.7-4.7 days at sea.[15] [edit] Behavior [edit] Reproduction California sea lions are highly social, and breed from May to June. When establishing a territory, the males will try to increase their chances of breeding by staying on the rookery for as long as possible.[16] During this time, they will fast, using their blubber as an energy store. Size is a key factor in winning fights as well as waiting. The bigger the male, the more blubber he can store, and the longer he can wait.[16] Before mating begins, females may form "milling" groups of two to 20 individuals. The females in these groups will mount each other and even the territorial male. Eventually, one or two of the females will mate and the milling stops.[17] The territorial and mating system of the California sea lion has been described as similar to a lek system.[17] The females choose their mates rather than the territories where the males are. A male sea lion can hold his territory for only up to 29 days.[16] Females do not become receptive until 21 days after the pups are born, thus the males do not set up their territories until after the females give birth.[16] Most fights occur during this time. Soon, the fights go from violent to ritualized displays, such as vocalizations, head-shaking, stares, and bluff lunges.[16] There can be as many as 16 females for one male. For adult males, territorial claims occur both on land and underwater. They have even been known to charge divers who enter their underwater territory. The females have a 12-month reproductive cycle, 9-month actual gestation with a 3-month delayed implantation of the fertilized egg after giving birth in early to mid-June. Mothers may give birth on land or in water. The pups are born with their eyes open and can vocalize with their mothers. Pups may nurse for up to six months, and grow rapidly due to the high fat content in the milk. California sea lions, along with other otariids and walruses, are possibly the only mammals whose milk does not contain lactose. At about two months, the pups learn to swim and hunt with their mothers. [edit] Communication California sea lions are well known for their dog-like barks. They are very vocal, particularly during the breeding season. Adult males make deep, loud barks repeatedly when establishing territories. After that, the males are mostly quiet unless their territorial boundaries have been violated by a rival. Barking may also attract mates. Female sea lions emit a unique vocalization when calling their pups, and the pups themselves will bleat and make a high pitched alarm call. Juveniles and subadults of both sexes will make high-pitched barks when alarmed. [edit] Nonbreeding activities After the breeding season, females normally stay in the breeding areas or migrate further south, while the adult males and juveniles generally migrate north for the winter. Social organization during the nonbreeding season is unstable.[18] However, a size-related dominance hierarchy does exist.[18] Large males use vocalization and movement to show their dominance, and smaller males always yield to them. Nonbreeding groups are gregarious on land and often squeeze together. Most sea lions found in man-made environments are males or juveniles, because sea lions do not breed there and those groups are more likely to migrate to those places during the nonbreeding season. [edit] Interactions with humans [edit] In entertainment Most of the iconic trained seals of circuses and marine parks are California sea lions. They are highly intelligent and can be trained to do different behaviors, such as throwing and catching balls on their noses, running up ladders, or honking horns in a musical fashion. Even adult males can be trained. Some groups, such as the Captive Animals Protection Society, object to using sea lions for entertainment, claiming the animals are used as "clowns" in unnatural environments and are simply gimmicks with no educational value.[19] On the other hand, people have claimed training captive sea lions has allowed them to experience just how intelligent they are. [edit] The California sea lion is used in military applications by the U.S. Navy Marine Mammal Program, including detecting naval mines and equipment recovery.[20] Sea lions can be highly useful as they can reach places inaccessible to human divers. They can dive to 1,000 feet (304.8 m) and swim silently and up to 25 miles per hour (40 km/h) in short bursts. Sea lions have been sent in the Persian Gulf to protect U.S. ships from enemy divers. The animals are trained to swim behind divers approaching a ship, and attach a clamp, which is connected to a rope, to the diver's leg. Navy officials say the sea lions can get the job done in seconds, and the enemy does not know the clamp was attached to his leg until it is too late.[21] [edit] Status In the United States, the Marine Mammal Protection Act (MMPA) protects California sea lions. Nevertheless, their population has increased and now conflicts with humans and other wildlife. They damage docks and boats (which, given sufficient numbers, can actually sink under the weight of the basking animals), steal fish from commercial boats, and attack and injure swimmers in San Francisco Bay.[22] In 2007, legislation amending the MMPA to permit their lethal removal from near salmon runs when their population exceeds their maximum sustainable level was introduced (HR 1769: Endangered Salmon Predation Prevention Act). The purpose of HR 1769 is to relieve pressure on the crashing Pacific Northwest salmon populations. Officially, pinnipeds (including sea lions) account for only an estimated 4%[23] of salmon loss in 2007. However, that figure comes from actual surface observation. Much predation occurs underwater, leading marine biologists to conclude the true rate is higher.[24] Short of lethal removal, attempts have been made to identify individual aggressive salmon predators, and to relocate them. Relocation generally fails because they simply return. In January 2008, at the request of Washington and Oregon, the National Marine Fisheries Service drafted a proposal to euthanize approximately 30 animals annually at Bonneville Dam.[24] The Humane Society of the United States brought suit, and the Ninth Circuit Court of Appeals ruled that the sea lions could be trapped and removed, but not killed.[25] From the Humane Society court case—NMFS's decision to authorize the killing of these animals is impossible to reconcile with: (1) NMFS's 2005 decision finding that fishermen's annual take of up to 17 percent of listed salmon is not significant and has only 'minimal adverse effects on Listed Salmonid ESUs in the Columbia River Basin'; (2) the States' 2008 decision to increase fishing quotas from 9 percent to 12 percent of the total spring run; and (3) NMFS's 2007 decision finding that hydroelectric dam take up to 60 percent of listed juvenile salmonids and up to 17 percent of listed adult salmonids 'meet[s] or exceed[s] the objectives of doing no harm and contributing to recovery with respect to the ESUs.'" In 2009, strandings of recently weaned pups increased three-fold. Lesser winds reduced ocean upwelling, which in turn reduced food supplies. Worse, poisonous domoic acid from algal blooms got into the sea lions' food chain. Nearly 3/4 of that June's 341 stranded pups died. Strandings were only a small part of a much larger problem. The National Marine Fisheries Service estimated the 2009 pup mortality rates were twice as high as those in 2008, again at 3/4 of the estimated 59,000 newborns.[27] California sea lions at the wharf in Santa Cruz, California California sea lion at Queens Zoo, New York [edit] References - ^ a b Aurioles, D. & Trillmich, F. (2008). Zalophus californianus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 30 January 2009. - ^ IMPACTS OF CALIFORNIA SEA LIONS AND PACIFIC HARBOR SEALS ON SALMONIDS AND WEST COAST ECOSYSTEMS, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, February 10, 1999; p. Appendix-7 - ^ Lowry, Mark S. and Karin A. Forney, Abundance and distribution of California sea lions (Zalophus californianus) in central and northern California during 1998 and summer 1999. Fishery Bulletin, Vol. - ^ William H. Burt and Richard P. Grossenheider, A Field Guide to the Mammals. Houghton Mifflin Company, Boston. Fiona A. Reed, A Field Guide to Mammals of North America North of Mexico. Houghton Mifflin Company, Boston. - ^ "California Sea Lion at Central Park Zoo". http://www.centralpark.com/pages/central-park-zoo/california-sea-lion.html. - ^ Don E. Wilson & DeeAnn M. Reeder (editors). Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed), Johns Hopkins University Press, 2,142 pp. Online - ^ http://www.nmfs.noaa.gov/pr/pdfs/sars/po2007slca.pdf - ^ Kindersley, Dorling (2001,2005). Animal. New York City: DK Publishing. - ^ a b Riedman, M. L. (2004). California Wildlife Habitat Relationships System: M170 California Sea Lion. - ^ Sea Lion Discovered Near Los Banos - ^ "Sea Lion Diet", Southwest Fisheries Science Center, 2/9/2007. - ^ R. A. Kastelein, N. M. Schooneman, N. Vaughan, P. R. Wiepkema, "Food consumption and growth of California sea lions (Zalophus californianus californianus), Zoo Biology, 19, 143-159. The Pinnipeds: Seals, Sea lions, and Walruses. Los Angeles, University of California Press. - ^ SeaLionPredation.com - news and information on seal and sea lion predation of salmon and steelhead in the Pacific Northwest - ^ Lowry, M. S. and J. V. Carretta "Market squid (Loligo opalescens) in the diet of California sea lions (Zalophus californianus) in southern California (1981-1995)", CalCOFI Rep., 1999, 40:196-207. - ^ a b c d e Odell, D. K. "The Fight to Mate: Breeding strategy of California sea lions", pg 172-173 of The Encyclopedia of Mammals, 2nd edition (2001) MacDonald, D. (ed) Oxford University Press. - ^ a b Heath, C. B. 1989. "The behavioral ecology of the California sea lion, Zalophus californianus". Ph.D. dissertation, University of California, Santa Cruz. - ^ a b Peterson, R. S. and Bartholomew, G. A. (1967). The Natural History and Behavior of the California Sea Lion. Special Publication No. 1, The American Society of Mammalogists. - ^ Captive sea lions "Navy may deploy anti-terrorism dolphins". Associated Press. Archived from the original on 2007-02-16. http://web.archive.org/web/20070216022617/http://news.yahoo.com/s/ap/20070213/ap_on_re_us/dolphin_defenders. "Sea lions called to duty in Persian Gulf". USA Today. http://www.usatoday.com/news/world/iraq/2003-02-16-sealions-usat_x.htm. - ^ "Rogue sea lion in S.F. menaces swimmers", San Francisco Chronicle, November 16, 2006, http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/11/16/MNGMFMDVGC1.DTL&hw=sea+lion&sn=011&sc=518 - ^ Reply to Questions from Representative Henry Brown, Hearing on HR 1769, “Endangered Salmon Predation Prevention Act”, August 2, 2007, p. 2. - ^ a b "Sea lions' death warrant?". http://www.oregonlive.com/news/oregonian/index.ssf?/base/news/1200632102166420.xml&coll=7. - ^ Sea lions removed to save salmon - Environment - MSNBC.com - ^ Humane Society vs Oregon Dept Fish and Wildlife - ^ "The Newsletter of the Marine Mammal Center: 29 (2). Fall/Winter 2009.". http://www.marinemammalcenter.org/pdfs/TMMC_FaWT%2009_rd6_color.pdf. Seals and Sea Lions of the World. New York: Facts on File. Marine Mammals of the World: Systematics and Distribution. In Special Publications of the Society for Marine Mammals no. 4. Lawrence: The Society for Marine Mammalogy. [edit] 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 - Peterson, Richard S; Bartholomew, George A. The natural history and behavior of the California sea lion (1967), [Stillwater, Okla.] American Society of Mammalogists [edit] External links - "Zalophus californianus". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=180621. Retrieved 23 March 2006. - WDFW Fact Sheet on sea lions - USACE information on sea lion deterrents - Animal Diversity Web - Zalophus californianus - Smithsonian Institution - North American Mammals: Zalophus californianus