Northern elephant seal

The northern elephant seal (Mirounga angustirostris) is one of two species of elephant seal (the other is the southern elephant seal). It is a member of the family Phocidae (true seals). Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating competition. Sexual dimorphism in size is great. Correspondingly, the mating system is highly polygynous; a successful male is able to impregnate up to 50 females in one season.

Northern elephant seal
Mating scene with elevated Alpha Male. Elephant Seals of Piedras Blancas
Male, female and pup
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Genus: Mirounga
Species:
M. angustirostris
Binomial name
Mirounga angustirostris
(Gill, 1866)
Mirounga angustirostris distribution
Distribution of the northern elephant seal (dark blue: breeding colonies; light blue: non-breeding individuals)

Description

Northern Elephant Seal Skull
Northern elephant seal skull on display at the Museum of Osteology, Oklahoma City, Oklahoma

The huge male northern elephant seal typically weighs 1,500–2,300 kg (3,300–5,100 lb) and measures 4–5 m (13–16 ft), although some males can weigh up to 3,700 kg (8,200 lb).[2] Females are much smaller and can range from 400 to 900 kg (880 to 1,980 lb) in weight, or roughly a third of the male's bulk, and measure from 2.5 to 3.6 m (8.2 to 11.8 ft).[3] The bull southern elephant seals are, on average, larger than those in the northern species, but the females in both are around the same size, indicating the even higher level of sexual dimorphism in the southern species.[4] Northern elephant seals typically live for around 9 years.[5] Both adult and juvenile elephant seals are bar-skinned and black before molting. After molting, they generally have a silver to dark gray coat that fades to brownish-yellow and tan. Adult males have hairless necks and chests speckled with pink, white, and light brown. Pups are mostly black at birth and molt to a silver gray after weaning.

The eyes are large, round, and black. The width of the eyes and a high concentration of low-light pigments suggest sight plays an important role in the capture of prey. Like all seals, elephant seals have atrophied hind limbs whose underdeveloped ends form the tail and tail fin. Each of the "feet" can deploy five long, webbed fingers. This agile, dual palm is used to propel water. The pectoral fins are used little while swimming. While their hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies. They are able to propel themselves quickly (as fast as 8 km/h) in this way for short-distance travel, to return to water, catch up with a female or chase an intruder.

Like other seals, elephant seals' bloodstreams are adapted to the cold in which a mixture of small veins surrounds arteries capturing heat from them. This structure is present in extremities such as the hindlimbs.

A unique characteristic of the northern elephant seal is that it has developed the ability to store oxygenated red blood cells within its spleen. In a 2004 study researchers used MRI to observe physiological changes of the spleens of 5 seal pups during simulated dives. By 3 minutes, the spleens on average contracted to a fifth of their original size, indicating a dive-related sympathetic contraction of the spleen. Also, a delay was observed between contraction of the spleen and increased hematocrit within the circulating blood, and attributed to the hepatic sinus. This fluid-filled structure is initially expanded due to the rush of RBC from the spleen and slowly releases the red blood cells into the circulatory system via a muscular vena caval sphincter found on the cranial aspect of the diaphragm. This ability to slowly introduce RBC into the blood stream is likely to prevent any harmful effects caused by a rapid increase in hematocrit.[6]

Range and ecology

E-seal Mom and pup, Piedras Blancas 2009
Mother and pup, Piedras Blancas

The northern elephant seal lives in the eastern Pacific Ocean. They spend most of their time at sea, and usually only come to land to give birth, breed, and molt. These activities occur at rookeries that are located on offshore islands or remote mainland beaches. The majority of these rookeries are in California and northern Baja California, ranging from Point Reyes National Seashore, California to Isla Natividad, Mexico.[7] Significant breeding colonies exist at Channel Islands, Año Nuevo State Reserve, Piedras Blancas Light, Morro Bay State Park and the Farallon Islands in the US,[8] and Isla Guadalupe, Isla Benito del Este and Isla Cedros in Mexico.[8] In recent decades the breeding range has extended northwards. In 1976 the first pup was found on Point Reyes and a breeding colony established there in 1981.[9] Since the mid-1990s some breeding has been observed at Castle Rock in Northern California and Shell Island off Oregon,[10] and in January 2009 the first elephant seal births were recorded in British Columbia at Race Rocks.[11] The California breeding population is now demographically isolated from the population in Baja California.[8]

Northern elephant seals exhibit extreme sexual dimorphism in their feeding behaviours. When the males leave their rookeries, they migrate northwards to their feeding grounds along the continental shelf from Washington to the western Aleutians in Alaska.[12][13] The males mostly feed on benthic organisms on the ocean floor.[12] When the females leave their rookeries, they head north or west into open ocean, and forage across a large area in the northeastern Pacific.[12] They have been recorded as far west as Hawaii.[12] Female elephant seals feed mainly on pelagic organisms in the water column.[12]

Vagrant elephant seals possibly appear on tropical regions such as at Mariana Islands.[14] Historical occurrences of elephant seal presence, residential or occasional, in western North Pacific are fairly unknown. There have been two records of vagrants visiting to Japanese coasts; a male on Niijima in 1989[15] (reference introducing a visit by a North Pacific right whale in 2011), and a young seal on beaches in Hasama, Tateyama in 2001[16] (where another right whale was seen in 2000). A 2.5 meter female was found on Sanze beach, Tsuruoka, Yamagata in October 2017, making it the first record from Sea of Japan. This individual was severely weakened but showing signs of recovery after receiving medications at Kamo Aquarium, and the aquarium is discussing whether or not to release her.[17] Some individuals have been observed on the coast of northeast Asia. Certain individuals established haul-out sites at the Commander Islands in the early 2000s; however, due to aggressive interactions with local Steller sea lions, long-term colonization is not expected.[18][19]

Mirounga angustirostris, Point Reyes
Adult male northern elephant seal at Point Reyes National Seashore, California

Female elephant seals forage in the open ocean, while male elephant seals forage along the continental shelf.[12] Males usually dive straight down to the ocean floor and stay at the bottom foraging for benthic prey.[12] The females hunt for pelagic prey in the open ocean, and dive deeper (up to 1700 m, though on average about 500 m) and stay down longer than the males.[20][12] Northern elephant seals eat a variety of prey, including mesopelagic fish such as myctophids, deep-water squid, Pacific hake, pelagic crustaceans, sharks, rays, and ratfish.[21][13][22] Octopoteuthis deletron squid are a common prey item, one study found this species in the stomachs of 58% of individuals sampled off the coast of California.[23] A female northern elephant seal was documented in 2013 by a deep sea camera at a depth of 894 m (2,933 ft), where it consumed a Pacific hagfish, slurping it up from the ocean floor. The event was reported by a Ukrainian boy named Kirill Dudko, who further reported the find to scientists in Canada.[24] Elephant seals do not need to drink, as they get their water from food and metabolism of fats.

While hunting in the dark depths, elephant seals seem to locate their prey at least partly by vision; the bioluminescence of some prey animals can facilitate their capture. Elephant seals do not have a developed a system of echolocation in the manner of cetaceans, but their vibrissae, which are sensitive to vibrations, are assumed to play a role in search of food. Males and females differ in diving behavior. Males tend to hug the continental shelf while making deep dives and forage along the bottom,[12] while females have more jagged routes and forage in the open ocean.[12] Elephant seals are prey for killer whales and white sharks. Both are most likely to hunt pups, and seldom hunt large bull elephant seals, but have taken seals of all ages. The shark, when hunting adults, is most likely to ambush a seal with a damaging bite and wait until it is weakened by blood loss to finish the kill.[25]

Social behavior and reproduction

Male elephant seals fighting for mates

Northern elephant seals return to their terrestrial breeding ground in December and January, with the bulls arriving first. The bulls haul out on isolated or otherwise protected beaches, typically on islands or very remote mainland locations. It is important that these beach areas offer protection from the winter storms and high surf wave action.[26] The bulls engage in fights of supremacy to determine which few bulls will achieve a harem.[27][28]

After the males have arrived to the beach, the females arrive to give birth. Females fast for five weeks and nurse their single pup for four weeks; in the last few days of lactation, females come into estrus and mate.[29] In this polygynous society, a high-ranking bull can have a harem of 30–100 cows, depending on his size and strength. Males unable to establish harems will wait on the periphery, and will try to mount nearby females.[27] Dominant bulls will disrupt copulations of lower-ranking bulls.[27] They can mount females without interference, but commonly break off to chase off rivals.[27] While fights are not usually to the death, they are brutal and often with significant bloodshed and injury; however, in many cases of mismatched opponents, the younger, less capable males are simply chased away, often to upland dunes. In a lifetime, a successful bull could easily sire over 500 pups. Most copulations in a breeding colony are done by only a small number of males and the rest may never be able to mate with a female.[28] Pups are sometimes crushed during battles between bulls.[26][28]

Three Mirounga angustirostris pups nursing
Three pups are nursing from a single adult female: Female elephant seals deliver only one pup; the two other may have wandered away from their mothers and gotten lost. In this situation, no pup would get enough milk.

After arrival on shore, males fast for three months, and females fast for five weeks during mating and when nursing their pups. The gestation period is about 11 months. Sometimes, a female can become very aggressive after giving birth and will defend her pup from other females.[30] Such aggression is more common in crowded beaches.[30] While most females nurse their own pups and reject nursings from alien pups, some do accept alien pups with their own.[26][29] An orphaned pup may try to find another female to suckle and some are adopted, at least on Año Nuevo Island.[26][29] Pups nurse about four weeks and are weaned abruptly before being abandoned by their mother, who heads out to sea within a few days. Left alone, weaned pups will gather into groups and stay on shore for 12 more weeks. The pups learn how to swim in the surf and eventually swim farther to forage. Thus, their first long journey at sea begins.

Elephant seals communicate though various means. Males will threaten each other with the snort, a sound caused by expelling air though their probosces, and the clap-trap, a loud, clapping sound comparable to the sound of a diesel engine.[31] Pups will vocalize when stressed or when prodding their mothers to allow them to suckle. Females make an unpulsed attraction call when responding to their young, and a harsh, pulsed call when threatened by other females, males or alien pups.[31] Elephant seals produce low-frequency sounds, both substrate-borne and air-borne. These sounds help maintain social hierarchy in crowded or noisy environments and reduce energy consumption when fasting.[31]

History and status

Breeding colony of Mirounga angustirostris
The northern elephant seal population was estimated to be 171,000 in 2005.[1]

Beginning in the 18th century, northern elephant seals were hunted extensively, almost to extinction by the end of the 19th century,[1] being prized for oil made from their blubber, and the population may have fallen as low as only 20-40 individuals.[1] In 1874, Charles Melville Scammon recorded in Marine Mammals of the Northwestern Coast of America, that an 18-ft-long bull caught on Santa Barbara Island yielded 210 gallons of oil.[32] They were thought to be extinct in 1884 until a remnant population of eight individuals was discovered on Guadalupe Island in 1892 by a Smithsonian expedition, who promptly killed seven of the eight for their collections.[33] The elephant seals managed to survive, and were finally protected by the Mexican government in 1922. Since the early 20th century, they have been protected by law in both Mexico and in the United States. Subsequently, the U.S. protection was strengthened after passage of the Marine Mammal Protection Act of 1972, and numbers have now recovered to over 100,000.

Nevertheless, a genetic bottleneck experienced by Northern elephant seals during nineteen century, could make them more susceptible to disease, environmental changes and pollution.[34][35] This bottleneck caused a sharp loss of genetic diversity and increased homozygosity in the surviving population, and also a decreased number of haplogroups.[36]

In California, the population is continuing to grow at around 6% per year, and new colonies are being established; they are now probably limited mostly by the availability of haul-out space. Their breeding was probably restricted to islands, before large carnivores were exterminated or prevented from reaching the side of the ocean.[37] Numbers can be adversely affected by El Niño events and the resultant weather conditions, and the 1997–98 El Niño may have caused the loss of about 80% of that year's pups. Presently, the northern elephant seal is protected under the federal Marine Mammal Protection Act and has a fully protected status under California law.

Populations of rookery sites in California have increased during the past century.[1] At Año Nuevo State Park, for example, no individuals were observed whatsoever until 1955; the first pup born there was observed in the early 1960s. Currently, thousands of pups are born every year at Año Nuevo, on both the island and mainland. The growth of the site near San Simeon has proved even more spectacular; no animals were there prior to 1990. Currently, the San Simeon site hosts more breeding animals than Año Nuevo State Park during winter season.

References

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External links

Asiatic linsang

The Asiatic linsang (Prionodon) is a genus comprising two species native to Southeast Asia: the banded linsang (Prionodon linsang) and the spotted linsang (Prionodon pardicolor). Prionodon is considered a sister taxon of the Felidae.

Año Nuevo State Park

Año Nuevo State Park is a state park of California, USA, encompassing Año Nuevo Island and Año Nuevo Point, which are known for their pinniped rookeries. Located in San Mateo County, the low, rocky, windswept point juts out into the Pacific Ocean about 55 miles (89 km) south of San Francisco and the Golden Gate. Año Nuevo State Natural Reserve, formerly a separate unit of the California state park system, was merged into Año Nuevo State Park in October 2008. The coastal geographic center, or coastal-midpoint of California is located at the Northern end of this park at N 37°09′58″, W 122°21'40", as the absolute geographic center of California falls at N 37°09′58″, W 119°26′58″W.The reserve contains a diversity of plant communities, including old growth forest, freshwater marsh, red alder riparian forest and knobcone pine forest. Its four perennial streams support steelhead and coho salmon, and its wetlands are habitat to the rare San Francisco garter snake and California red-legged frog. Cultural resources include the remnants of a prehistoric Native American village site and a number of structures from the 19th century Cascade Ranch. In conjunction with adjacent and nearby public lands, the unit permits the protection of important regional ecological corridors.

The point remains undeveloped, much as Sebastián Vizcaíno saw it from his passing ship in 1603.

Earless seal

The earless seals, phocids or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.

Elephant seal

Elephant seals are large, oceangoing earless seals in the genus Mirounga. The two species, the northern elephant seal (M. angustirostris) and the southern elephant seal (M. leonina), were both hunted to the brink of extinction by the end of the 19th century, but the numbers have since recovered.

The northern elephant seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico. The most northerly breeding location on the Pacific Coast is at Race Rocks, at the southern tip of Vancouver Island in the Strait of Juan de Fuca. The southern elephant seal is found in the Southern Hemisphere on islands such as South Georgia and Macquarie Island, and on the coasts of New Zealand, South Africa, and Argentina in the Peninsula Valdés. In southern Chile, there is a small colony of 120 animals at Jackson Bay, Admiralty Sound (Seno Almirantazgo), Tierra del Fuego. The oldest known unambiguous elephant seal fossils are fragmentary fossils of an unnamed member of the tribe Miroungini described from the late Pliocene Petane Formation of New Zealand. Teeth originally identified as representing an unnamed species of Mirounga have been found in South Africa, and dated to the Miocene epoch; however Boessenecker & Churchill (2016) considered these teeth to be almost certainly misidentified odontocete teeth.Elephant seals breed annually and are seemingly faithful to colonies that have established breeding areas.

Fauna of California

The fauna of the State of California may be the most diverse in the United States of America. Of the Lower 48 conterminous states, California has the greatest diversity in climate, terrain and geology in general. The state's six life zones are the lower Sonoran (desert); upper Sonoran (foothill regions and some coastal lands); transition (coastal areas and moist northeastern counties); and the Canadian, Hudsonian, and Arctic zones, comprising California's highest elevations. California’s diverse geography gives rise to dozens of different ecosystems, each of which has its own unique native plants and animals. California is a huge state, the 3rd largest in the U.S., and can range broadly in habitat type.Earth scientists typically divide California into eleven distinct geomorphic provinces with clearly defined boundaries. They are, from north to south, the Klamath Mountains, the Cascade Range, the Modoc Plateau, the Basin and Range, the Coast Ranges, the Central Valley, the Sierra Nevada, the Transverse Ranges, the Mojave Desert, the Peninsular Ranges, and the Colorado Desert. Here, the Los Angeles Basin, the Channel Islands, and the Pacific Ocean are treated as distinct regions.

Common animals that live throughout all the state include raccoons, weasels, otters, beavers, hawks, lizards, owls, coyotes, skunks, snakes, cougars, black bears, deers, squirrels and whales. As of 2013, there are 634 bird species on the California Birds Records Committee, ten of which are introduced species which are not native to the state. The California quail, the official state bird, has a breeding habit of mainly shrubby areas and open woodland. Another bird which winters in California is the American white pelican which is a large seabird, with a wingspan reaching up to 110 inches (280 cm).

Venomous spiders in California include Arizona recluse, baja recluse, chilean recluse, desert recluse, martha's recluse, russell's recluse, brown widow and western black widow.

Ferret-badger

Ferret-badgers are the five species of the genus Melogale, which is the only genus of the monotypic mustelid subfamily Helictidinae.

Bornean ferret-badger (Melogale everetti)

Chinese ferret-badger (Melogale moschata)

Javan ferret-badger (Melogale orientalis)

Burmese ferret-badger (Melogale personata)

Vietnam ferret-badger (Melogale cucphuongensis)

Guadalupe Island

Guadalupe Island or Isla Guadalupe is a volcanic island 250 km² and located 241 kilometres (150 mi) off the west coast of Mexico's Baja California Peninsula and some 400 kilometres (250 mi) southwest of the city of Ensenada in the state of Baja California, in the Pacific Ocean. The two other Mexican island groups in the Pacific Ocean that are not on the continental shelf are Revillagigedo Islands and Rocas Alijos. Guadalupe Island and its islets are the westernmost region of Mexico.

List of Arctic pinnipeds

This is a list of Arctic pinnipeds:

Phocidae (ᓇᑦᓯᖅ, natsiq)Bearded seal (ᐅᒡᔪᒃ, ᐅᒥᒃᑑᖅ, ugjuk) Erignathus barbatus

Hooded seal (ᓇᑦᓯᕙᒃ, natsivak) Cystophora cristata

Harbor seal (ᖃᓯᒋᐊᖅ, qasigiaq) Phoca vitulina

Harp seal (ᖃᐃᕈᓕᒃ, qairulik) Pagophilus groenlandicus

Grey seal (ᐳᕕᓲᖅ, puvisuuq) Halichoerus grypus

Ringed seal (ᓇᑦᑎᖅ, nattiq) Pusa hispida

Northern elephant seal Mirounga angustirostris

Ribbon seal (Histriophoca fasciata)

Spotted seal (Phoca largha, Phoca vitulina largha)

Otariidae

Northern fur seal (Callorhinus ursinus)

OdobenidaeWalrus (ᐊᐃᕕᖅ, aiviq) Odobenus rosmarus

List of National Natural Landmarks in California

From List of National Natural Landmarks, these are the National Natural Landmarks in California. There are 36 in total.

Lutrogale

Lutrogale is a genus of otters, with only one extant species—the smooth-coated otter.

Marine mammal

Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a polyphyletic relation due to convergent evolution, as in they do not have an immediate common ancestor. They are also unified by their reliance on the marine environment for feeding.

Marine mammal adaptation to an aquatic lifestyle varies considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water but need to return to land for important activities such as mating, breeding and molting. In contrast, both otters and the polar bear are much less adapted to aquatic living. Their diet varies considerably as well; some may eat zooplankton, others may eat fish, squid, shellfish, sea-grass and a few may eat other mammals. While the number of marine mammals is small compared to those found on land, their roles in various ecosystems are large, especially concerning the maintenance of marine ecosystems, through processes including the regulation of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently threatened.

Marine mammals were first hunted by aboriginal peoples for food and other resources. Many were also the target for commercial industry, leading to a sharp decline in all populations of exploited species, such as whales and seals. Commercial hunting led to the extinction of †Steller's sea cow, †sea mink, †Japanese sea lion and the Caribbean monk seal. After commercial hunting ended, some species, such as the gray whale and northern elephant seal, have rebounded in numbers; conversely, other species, such as the North Atlantic right whale, are critically endangered. Other than hunting, marine mammals can be killed as bycatch from fisheries, where they become entangled in fixed netting and drown or starve. Increased ocean traffic causes collisions between fast ocean vessels and large marine mammals. Habitat degradation also threatens marine mammals and their ability to find and catch food. Noise pollution, for example, may adversely affect echolocating mammals, and the ongoing effects of global warming degrade arctic environments.

Nyctereutes

Nyctereutes is an Old World genus of the family Canidae, consisting of just one living species, the raccoon dog of East Asia. Nyctereutes appeared about 9.0 million years ago (Mya), with all but one species becoming extinct before the Pleistocene.

Native to East Asia, the raccoon dog has been intensively bred for fur in Europe and especially in Russia during the twentieth century. Specimens have escaped or have been introduced to increase production and formed populations in Eastern Europe. It is currently expanding rapidly in the rest of Europe, where its presence is undesirable because it is considered to be a harmful and invasive species.

Ojo de Liebre Lagoon

Ojo de Liebre Lagoon (formerly known as Scammon's Lagoon), translated into English as "hare eye lagoon", is a coastal lagoon located in Mulegé Municipality near the town of Guerrero Negro in the northwestern Baja California Sur state of Mexico. It lies approximately halfway between the southern tip of the Baja California Peninsula and the U.S.-Mexico border, opening onto the Pacific Ocean.

The lagoon is within the Vizcaíno Biosphere Reserve UNESCO World Heritage Site, and is a Ramsar wetlands site. It also is the site of the biggest commercial saltworks plant in the world. It is an important habitat for the reproduction and wintering of the gray whale and harbor seal, as well as other marine mammals including the California sea lion, northern elephant seal and blue whale. Four species of endangered marine turtles reproduce there. It is an important refuge for waterfowl in the winter.Encompassing both a UNESCO World Heritage Site and a major salt plant, Laguna Ojo de Liebre embodies the diverse worlds of natural habitat and industrialization.Tourism, now closely controlled, was formerly a threat to the gray whales.

Pinniped

Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals). There are 33 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their closest living relatives are believed to be bears and the superfamily of musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago.

Seals range in size from the 1 m (3 ft 3 in) and 45 kg (99 lb) Baikal seal to the 5 m (16 ft) and 3,200 kg (7,100 lb) southern elephant seal, which is also the largest member of the order Carnivora. Several species exhibit sexual dimorphism. They have streamlined bodies and four limbs that are modified into flippers. Though not as fast in the water as dolphins, seals are more flexible and agile. Otariids use their front limbs primarily to propel themselves through the water, while phocids and walruses use their hind limbs. Otariids and walruses have hind limbs that can be pulled under the body and used as legs on land. By comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible external ears, while phocids and walruses lack these. Pinnipeds have well-developed senses—their eyesight and hearing are adapted for both air and water, and they have an advanced tactile system in their whiskers or vibrissae. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water, and, other than the walrus, all species are covered in fur.

Although pinnipeds are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres. They spend most of their lives in the water, but come ashore to mate, give birth, molt or escape from predators, such as sharks and killer whales. They feed largely on fish and marine invertebrates; but a few, like the leopard seal, feed on large vertebrates, such as penguins and other seals. Walruses are specialized for feeding on bottom-dwelling mollusks. Male pinnipeds typically mate with more than one female (polygyny), although the degree of polygyny varies with the species. The males of land-breeding species tend to mate with a greater number of females than those of ice breeding species. Male pinniped strategies for reproductive success vary between defending females, defending territories that attract females and performing ritual displays or lek mating. Pups are typically born in the spring and summer months and females bear almost all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively short period of time while others take foraging trips at sea between nursing bouts. Walruses are known to nurse their young while at sea. Seals produce a number of vocalizations, notably the barks of California sea lions, the gong-like calls of walruses and the complex songs of Weddell seals.

The meat, blubber and fur coats of pinnipeds have traditionally been used by indigenous peoples of the Arctic. Seals have been depicted in various cultures worldwide. They are commonly kept in captivity and are even sometimes trained to perform tricks and tasks. Once relentlessly hunted by commercial industries for their products, seals and walruses are now protected by international law. The Japanese sea lion and the Caribbean monk seal have become extinct in the past century, while the Mediterranean monk seal and Hawaiian monk seal are ranked endangered by the International Union for Conservation of Nature. Besides hunting, pinnipeds also face threats from accidental trapping, marine pollution, and conflicts with local people.

Population bottleneck

A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events (such as famines, earthquakes, floods, fires, disease, or droughts) or human activities (such as genocide). Such events can reduce the variation in the gene pool of a population; thereafter, a smaller population, with a smaller genetic diversity, remains to pass on genes to future generations of offspring through sexual reproduction. Genetic diversity remains lower, increasing only when gene flow from another population occurs or very slowly increasing with time as random mutations occur. This results in a reduction in the robustness of the population and in its ability to adapt to and survive selecting environmental changes, such as climate change or a shift in available resources. Alternatively, if survivors of the bottleneck are the individuals with the greatest genetic fitness, the frequency of the fitter genes within the gene pool is increased, while the pool itself is reduced.

The genetic drift caused by a population bottleneck can change the proportional random distribution of alleles and even lead to loss of alleles. The chances of inbreeding and genetic homogeneity can increase, possibly leading to inbreeding depression. Smaller population size can also cause deleterious mutations to accumulate.A slightly different form of bottleneck can occur if a small group becomes reproductively (e.g. geographically) separated from the main population, such as through a founder event, e.g. if a few members of a species successfully colonize a new isolated island, or from small captive breeding programs such as animals at a zoo. Alternatively, invasive species can undergo population bottlenecks through founder events when introduced into their invaded range.Population bottlenecks play an important role in conservation biology (see minimum viable population size) and in the context of agriculture (biological and pest control).

San Simeon, California

San Simeon (ZIP Code: 93452; area code 805) is a town and census-designated place on the Pacific coast of San Luis Obispo County, California. Its position along State Route 1 is about halfway between Los Angeles and San Francisco, each of those cities being roughly 230 mi (370 km) away. A key feature of the area is Hearst Castle, a hilltop mansion built by William Randolph Hearst in the early 20th century that is now a tourist attraction. The area is also home to a large northern elephant seal rookery, known as the Piedras Blancas rookery. It is located 7 mi north of San Simeon on Highway 1.

Southern elephant seal

The southern elephant seal (Mirounga leonina) is one of the two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. It gets its name from its massive size and the large proboscis of the adult male, which is used to produce very loud roars, especially during the breeding season. A bull southern elephant seal is about 40% heavier than a male northern elephant seal (Mirounga angustirostris), more than twice as heavy as a male walrus (Odobenus rosmarus), and six to seven times heavier than the largest living terrestrial carnivorans, the polar bear (Ursus maritimus) and the Kodiak bear (Ursus arctos middendorffi).

The Marine Mammal Center

The Marine Mammal Center is a private, non-profit U.S. organization that was established in 1975 for the purpose of rescuing, rehabilitating, and releasing, marine mammals who are injured, ill, or abandoned. It was founded in Sausalito, California by Lloyd Smalley, Pat Arrigoni, and Paul Maxwell. Since 1975 they rescued over 20,000 marine mammals. It also serves as a center for environmental research and education regarding marine mammals, namely cetaceans (whales and dolphins) and pinnipeds (seals, fur seals, and sea lions). Marine mammal abandonment refers to maternal separation; pups that have been separated from their mother before weaning. At the center, they receive specialized veterinary care; diagnosed, treated, rehabilitated, and ideally, released back into the wild. Animals in need of assistance are usually identified by a member of the public who has contacted the center. These animals represent the following major species: California sea lion, northern elephant seal, Pacific harbor seal, northern fur seal, and the southern sea otter. On a few occasions, the Marine Mammal Center has taken in Guadeloupe fur seals, Steller sea lions, and bottlenose/Pacific white-sided dolphins. The only non-mammals that the center takes in are sea turtles.

Extant Carnivora species

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