title: Hexagon content: a regular dodecagon by adding alternating squares and equilateral triangles around it. This pattern repeats within the rhombitrihexagonal tiling. From bees' honeycombs to the Giant's Causeway, hexagonal patterns are prevalent in nature due to their efficiency. In a hexagonal grid each line is as short as it can possibly be if a large area is to be filled with the fewest number of hexagons. This means that honeycombs require less wax to construct and gain lots of strength under compression. Irregular hexagons with parallel opposite edges are called parallelogons and can also tile the plane by translation. In three dimensions,


title: Hexagon content: hexagonal prisms with parallel opposite faces are called parallelohedrons and these can tessellate 3-space by translation. In addition to the regular hexagon, which determines a unique tessellation of the plane, any irregular hexagon which satisfies the Conway criterion will tile the plane. Pascal's theorem (also known as the "Hexagrammum Mysticum Theorem") states that if an arbitrary hexagon is inscribed in any conic section, and pairs of opposite sides are extended until they meet, the three intersection points will lie on a straight line, the "Pascal line" of that configuration. The Lemoine hexagon is a cyclic hexagon (one inscribed in a


title: Hexagon content: circle) with vertices given by the six intersections of the edges of a triangle and the three lines that are parallel to the edges that pass through its symmedian point. If the successive sides of a cyclic hexagon are "a", "b", "c", "d", "e", "f", then the three main diagonals intersect in a single point if and only if . If, for each side of a cyclic hexagon, the adjacent sides are extended to their intersection, forming a triangle exterior to the given side, then the segments connecting the circumcenters of opposite triangles are concurrent. If a hexagon has vertices


title: Hexagon content: on the circumcircle of an acute triangle at the six points (including three triangle vertices) where the extended altitudes of the triangle meet the circumcircle, then the area of the hexagon is twice the area of the triangle. Let ABCDEF be a hexagon formed by six tangent lines of a conic section. Then Brianchon's theorem states that the three main diagonals AD, BE, and CF intersect at a single point. In a hexagon that is tangential to a circle and that has consecutive sides "a", "b", "c", "d", "e", and "f", If an equilateral triangle is constructed externally on each


title: Hexagon content: side of any hexagon, then the midpoints of the segments connecting the centroids of opposite triangles form another equilateral triangle. A skew hexagon is a skew polygon with 6 vertices and edges but not existing on the same plane. The interior of such an hexagon is not generally defined. A "skew zig-zag hexagon" has vertices alternating between two parallel planes. A regular skew hexagon is vertex-transitive with equal edge lengths. In 3-dimensions it will be a zig-zag skew hexagon and can be seen in the vertices and side edges of a triangular antiprism with the same D, [2,6] symmetry, order


title: Hexagon content: 12. The cube and octahedron (same as triangular antiprism) have regular skew hexagons as petrie polygons. The regular skew hexagon is the Petrie polygon for these higher dimensional regular, uniform and dual polyhedra and polytopes, shown in these skew orthogonal projections: A "principal diagonal" of a hexagon is a diagonal which divides the hexagon into quadrilaterals. In any convex equilateral hexagon (one with all sides equal) with common side "a", there exists a principal diagonal "d" such that and a principal diagonal "d" such that There is no Platonic solid made of only regular hexagons, because the hexagons tessellate, not


title: Hexagon content: allowing the result to "fold up". The Archimedean solids with some hexagonal faces are the truncated tetrahedron, truncated octahedron, truncated icosahedron (of soccer ball and fullerene fame), truncated cuboctahedron and the truncated icosidodecahedron. These hexagons can be considered truncated triangles, with Coxeter diagrams of the form and . There are other symmetry polyhedra with stretched or flattened hexagons, like these Goldberg polyhedron G(2,0): There are also 9 Johnson solids with regular hexagons: Hexagon In geometry, a hexagon (from Greek ἕξ "hex", "six" and γωνία, "gonía", "corner, angle") is a six-sided polygon or 6-gon. The total of the internal angles of


title: Menorca content: Theodore, a rich representative Jew who stood high in the estimation of his coreligionists and of Christians alike, underwent baptism. The act of conversion brought about, within a previously peaceful coexisting community, the expulsion of the ruling Jewish elite into the bleak hinterlands, the burning of synagogues, and the gradual reinstatement of certain Jewish families after the forced acceptance of Christianity, allowing the survival of those Jewish families who had not already perished. Many Jews remained within the Jewish faith while outwardly professing Christian faith. Some of these Jews form part of the Xueta community. When Menorca became a British


title: "Politics of the Netherlands" content: and 1813). Before 1917, the Netherlands had a two-round system with census suffrage (per the constitution of 1814), in which only property-owning adult males had the right to vote. Under influence of the rising socialist movement the requirements were gradually reduced until in 1917 the present voting system of a representative democracy with male universal suffrage was instituted, expanded in 1919 to include women. Until 1966, Dutch politics were characterised by pillarisation: society was separated in several segments (pillars) which lived separate from each other and there was only contact at the top levels, in government. These pillars had their


title: Farm content: In the UK, "farm" as an agricultural unit, always denotes the area of pasture and other fields together with its farmhouse, farmyard and outbuildings. Large farms, or groups of farms under the same ownership, may be called an estate. Conversely, a small farm surrounding the owner's dwelling is called a smallholding and is generally focused on self-sufficiency with only the surplus being sold. A farm in Africa includes various structures. Depending on climate-related areas primarily farming is the raising and breeding of grazing livestock, such as cattle, sheep, ostriches, horses or goats. Predominantly domestic animals are raised for their meat,


title: Dugong content: Dugong The dugong (; "Dugong dugon") is a medium-sized marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow ("Hydrodamalis gigas"), was hunted to extinction in the 18th century. The dugong is the only strictly herbivorous marine mammal. The dugong is the only sirenian in its range, which spans the waters of some 40 countries and territories throughout the Indo-West Pacific. The dugong is largely dependent on seagrass communities for subsistence and


title: Dugong content: is thus restricted to the coastal habitats which support seagrass meadows, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as bays, mangrove channels, the waters of large inshore islands and inter-reefal waters. The northern waters of Australia between Shark Bay and Moreton Bay are believed to be the dugong's contemporary stronghold. Like all modern sirenians, the dugong has a body with no dorsal fin or hind limbs. The forelimbs or flippers are paddle-like. The dugong is easily distinguished from the manatees by its fluked, dolphin-like tail, but also possesses a unique skull and teeth. Its


title: Dugong content: snout is sharply downturned, an adaptation for feeding in benthic seagrass communities. The molar teeth are simple and peg-like unlike the more elaborate molar dentition of manatees. The dugong has been hunted for thousands of years for its meat and oil. Traditional hunting still has great cultural significance in several countries in its modern range, particularly northern Australia and the Pacific Islands. The dugong's current distribution is fragmented, and many populations are believed to be close to extinction. The IUCN lists the dugong as a species vulnerable to extinction, while the Convention on International Trade in Endangered Species limits or


title: Dugong content: bans the trade of derived products. Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include fishing-related fatalities, habitat degradation and hunting. With its long lifespan of 70 years or more, and slow rate of reproduction, the dugong is especially vulnerable to extinction. The word "dugong" derives from the Visayan (probably Cebuano) "dugung". The name was first adopted and popularized by the French naturalist Georges-Louis Leclerc, Comte de Buffon, as ""dugon"" in "Histoire Naturelle" (1765), after descriptions of the animal from the island of Leyte in the Philippines. Other common local names include


title: Dugong content: "sea cow", "sea pig" and "sea camel". "Dugong dugon" is the only extant species of the family Dugongidae, and one of only four extant species of the Sirenia order, the others forming the manatee family. It was first classified by Müller in 1776 as "Trichechus dugon", a member of the manatee genus previously defined by Linnaeus. It was later assigned as the type species of "Dugong" by Lacépède and further classified within its own family by Gray and subfamily by Simpson. Dugongs and other sirenians are not closely related to other marine mammals, being more related to elephants. Dugongs and


title: Dugong content: elephants share a monophyletic group with hyraxes and the aardvark, one of the earliest offshoots of eutherians. The fossil record shows sirenians appearing in the Eocene, where they most likely lived in the Tethys Ocean. The two extant families of sirenians are thought to have diverged in the mid-Eocene, after which the dugongs and their closest relative, the Steller's sea cow, split off from a common ancestor in the Miocene. The Steller's sea cow became extinct in the 18th century. No fossils exist of other members of the Dugongidae. Molecular studies have been made on dugong populations using mitochondrial DNA.


title: Dugong content: The results have suggested that the population of Southeast Asia is distinct from the others. Australia has two distinct maternal lineages, one of which also contains the dugongs from Africa and Arabia. Limited genetic mixing has taken place between those in Southeast Asia and those in Australia, mostly around Timor. One of the lineages stretches all the way from Moreton Bay to Western Australia, while the other only stretches from Moreton Bay to the Northern Territory. There is not yet sufficient genetic data to make clear boundaries between distinct groups. The dugong's body is large with a cylindrical shape that


title: Dugong content: tapers at both ends. It has thick, smooth skin that is a pale cream colour at birth, but darkens dorsally and laterally to brownish-to-dark-grey with age. The colour of a dugong can change due to the growth of algae on the skin. The body is sparsely covered in short hair, a common feature among sirenians which may allow for tactile interpretation of their environment. These hairs are most developed around the mouth, which has a large horseshoe-shaped upper lip forming a highly mobile muzzle. This muscular upper lip aids the dugong in foraging. The dugong's tail flukes and flippers are


title: Dugong content: similar to those of dolphins. These flukes are raised up and down in long strokes to move the animal forward, and can be twisted to turn. The forelimbs are paddle-like flippers which aid in turning and slowing. The dugong lacks nails on its flippers, which are only 15% of a dugong's body length. The tail has deep notches. A dugong's brain weighs a maximum of , about 0.1% of the animal's body weight. With very small eyes, dugongs have limited vision, but acute hearing within narrow sound thresholds. Their ears, which lack pinnae, are located on the sides of their


title: Dugong content: head. The nostrils are located on top of the head and can be closed using valves. Dugongs have two teats, one located behind each flipper. There are few differences between sexes; the body structures are almost the same. A male's testes are not externally located, and the main difference between males and females is the location of the genital aperture in relation to the umbilicus and the anus. The lungs in a dugong are very long, extending almost as far as the kidneys, which are also highly elongated in order to cope with the saltwater environment. If wounded, a dugong's


title: Dugong content: blood will clot rapidly. The skull of a dugong is unique. The skull is enlarged with sharply down-turned premaxilla, which are stronger in males. The spine has between 57 and 60 vertebrae. Unlike in manatees, the dugong's teeth do not continually grow back via horizontal tooth replacement. The dugong has two incisors (tusks) which emerge in males during puberty. The female's tusks continue to grow without emerging during puberty, sometimes erupting later in life after reaching the base of the premaxilla. The number of growth layer groups in a tusk indicates the age of a dugong, and the cheekteeth move


title: Dugong content: forward with age. The full dental formula of dugongs is , meaning they have two incisors, three premolars, and three molars on each side of their upper jaw, and three incisors, one canine, three premolars, and three molars on each side of their lower jaw. Like other sirenians, the dugong experiences pachyostosis, a condition in which the ribs and other long bones are unusually solid and contain little or no marrow. These heavy bones, which are among the densest in the animal kingdom, may act as a ballast to help keep sirenians suspended slightly below the water's surface. An adult's


title: Dugong content: length rarely exceeds . An individual this long is expected to weigh around . Weight in adults is typically more than and less than . The largest individual recorded was long and weighed , and was found off the Saurashtra coast of west India. Females tend to be larger than males. Dugongs are found in warm coastal waters from the western Pacific Ocean to the eastern coast of Africa, along an estimated of coastline between 26° and 27° degrees to the north and south of the equator. Their historic range is believed to correspond to that of seagrasses from the


title: Dugong content: Potamogetonaceae and Hydrocharitaceae families. The full size of the former range is unknown, although it is believed that the current populations represent the historical limits of the range, which is highly fractured. Today populations of dugongs are found in the waters of 37 countries and territories. Recorded numbers of dugongs are generally believed to be lower than actual numbers, due to a lack of accurate surveys. Despite this, the dugong population is thought to be shrinking, with a worldwide decline of 20 per cent in the last 90 years. They have disappeared from the waters of Hong Kong, Mauritius, and


title: Dugong content: Taiwan, as well as parts of Cambodia, Japan, the Philippines and Vietnam. Further disappearances are likely. Dugongs are generally found in warm waters around the coast with large numbers concentrated in wide and shallow protected bays. The dugong is the only strictly-marine herbivorous mammal, as all species of manatee utilise fresh water to some degree. Nonetheless, they can tolerate the brackish waters found in coastal wetlands, and large numbers are also found in wide and shallow mangrove channels and around leeward sides of large inshore islands, where seagrass beds are common. They are usually located at a depth of around


title: Dugong content: , although in areas where the continental shelf remains shallow dugongs have been known to travel more than from the shore, descending to as far as , where deepwater seagrasses such as "Halophila spinulosa" are found. Special habitats are used for different activities. It has been observed that shallow waters are used as sites for calving, minimising the risk of predation. Deep waters may provide a thermal refuge from cooler waters closer to the shore during winter. In the late 1960s, herds of up to 500 dugongs were observed off the coast of East Africa and nearby islands. Current populations


title: Dugong content: in this area are extremely small, numbering 50 and below, and it is thought likely they will become extinct. The eastern side of the Red Sea is home to large populations numbering in the hundreds, and similar populations are thought to exist on the western side. In the 1980s, it was estimated there could be as many as 4,000 dugongs in the Red Sea. The Persian Gulf has the second-largest dugong population in the world, inhabiting most of the southern coast, and the current population is believed to number "c." 7,500. However, recent studies revealed severe declines both in population


title: Dugong content: size and distributions among the region. Dugong populations in Madagascar are poorly studied, but due to widespread exploitation it is thought they may have severely declined, with few surviving individuals. In Mozambique, most of the remaining local populations are very small and the largest (about 120 individuals) occurs at Bazaruto Island, but they have become rare in historical habitats such as in Maputo Bay and on Inhaca Island. In Tanzania, observations have recently been increased around the Mafia Island Marine Park where a hunt was intended by fishermen but failed in 2009. In the Seychelles, dugongs had been regarded as


title: Dugong content: extinct in 18th century until a small number was discovered around the Aldabra Atoll. This population may belong to a different group than that distributed among the inner isles. Dugongs once thrived among the Chagos Archipelago and Sea Cow Island was named after the species, although the species no longer occurs in the region. A highly isolated breeding population exists in the Marine National Park, Gulf of Kutch, the only remaining population in western India. It is from the population in the Persian Gulf, and from the nearest population in India. Former populations in this area, centred on the Maldives


title: Dugong content: and the Laccadive Islands, are presumed to be extinct. A population exists in the Gulf of Mannar Marine National Park and the Palk Strait between India and Sri Lanka, but it is seriously depleted. Recoveries of seagrass beds along former ranges of dugongs, such as the Chilika Lake have been confirmed in recent years, rising hopes for re-colorizations of the species. The population around the Andaman and Nicobar Islands are known only from a few records, and although the population was large during British rule, it is now believed to be small and scattered. Once distributed throughout the coastal belt


title: Dugong content: in Sri Lanka, the dugong numbers have declined in last two decades. A small population exists today along the southern coast of China, where efforts are being made to protect it, including ranging in Guangxi. Despite these efforts, numbers continue to decrease, and in 2007 it was reported that no more dugong could be found on the west coast of the island of Hainan. Historically, dugongs were also present in the southern parts of the Yellow Sea. In Vietnam, dugongs have been restricted mostly to the provinces of Kiên Giang and Bà Rịa–Vũng Tàu, including Phu Quoc Island and Con


title: Dugong content: Dao Island, which hosted large populations in the past. Con Dao is now the only site in Vietnam where dugong are regularly seen, protected within the Côn Đảo National Park. Nonetheless, dangerously low levels of awarenesses for conservation of marine organisms in Vietnam and Cambodia may result in increased intentional or unintentional catches, and illegal trade is a potential danger for local dugongs. On Phu Quoc, the first 'Dugong Festival' was held in 2014, aiming to raise awareness of these issues. In Thailand, the present distribution of dugongs is restricted to 6 provinces along the Andaman Sea, and very few


title: Dugong content: dugongs are present in the Gulf of Thailand. The Gulf of Thailand was historically home to large number of the animals, but none have been sighted in the west of the gulf in recent years, and the remaining population in the east is thought to be very small and possibly declining. Dugongs are believed to exist in the Straits of Johor in very small numbers. The waters around Borneo support a small population, with more scattered throughout the Malay archipelago. All the islands of the Philippines are believed to have once provided habitats for dugongs, which were common until the


title: Dugong content: 1970s. Populations exist around the Solomon Islands archipelago and New Caledonia, stretching to an easternmost population in Vanuatu. A highly isolated population lives around the islands of Palau. A single dugong lives at Cocos (Keeling) Islands although the animal is thought to be a vagrant. Today, possibly the smallest and northernmost population of dugongs exists around the Ryukyu islands, and a population formerly existed off Taiwan. An endangered population of 50 or fewer dugongs, possibly as few as three individuals, survives around Okinawa. New sightings of a cow-calf pair have been reported in 2017, indicating a possible breeding had occurred


title: Dugong content: in these waters. A single individual was recorded in Amami Oshima, at the northernmost edge of the dugong's historic range, more than 40 years after the last previous recorded sighting. A vagrant strayed into port near Ushibuka, Kumamoto, and died due to poor health. Historically, the Yaeyama Islands held a large concentration of dugongs, with more than 300 individuals. On Aragusuku Island, large quantities of skulls are preserved at an utaki that outsiders are strictly forbidden to enter. Dugong populations in these areas were reduced by historical hunts as payments to the Ryukyu Kingdom, before being wiped out because of


title: Dugong content: large-scale illegal hunting and fishing using destructive methods such as dynamite fishing after the Second World War. Populations around Taiwan appear to be almost extinct, although remnant individuals may visit areas with rich seagrass beds such as Dongsha Atoll. Some of the last reported sightings were made in Kenting National Park in 1950s and 60s. There had been occasional records of vagrants at the Northern Mariana Islands prior to 1985. It is unknown how much mixing there was between these populations historically. Some theorise that populations existed independently, for example that the Okinawan population were isolated members derived from the


title: Dugong content: migration of a Philippine subspecies. Others postulate that the populations formed part of a super-population where migration between Ryukyu, Taiwan, and the Philippines was common. Australia is home to the largest population, stretching from Shark Bay in Western Australia to Moreton Bay in Queensland. The population of Shark Bay is thought to be stable with over 10,000 dugongs. Smaller populations exist up the coast, including one in Ashmore reef. Large numbers of dugongs live to the north of the Northern Territory, with a population of over 20,000 in the gulf of Carpentaria alone. A population of over 25,000 exists in


title: Dugong content: the Torres Strait such as off Thursday Island, although there is significant migration between the strait and the waters of New Guinea. The Great Barrier Reef provides important feeding areas for the species; this reef area houses a stable population of around 10,000, although the population concentration has shifted over time. Large bays facing north on the Queensland coast provide significant habitats for dugong, with the southernmost of these being Hervey Bay and Moreton Bay. Dugongs had been occasional visitors along the Gold Coast where an (re)establishment of a local population through range expansions has started recently. It has been


title: Dugong content: confirmed that dugongs once inhabited the water of the Mediterranean possibly until after the rise of civilizations along the inland sea. This population possibly shared ancestry with the Red Sea population, and the Mediterranean population had never been large due to geographical factors and climate changes. The Mediterranean is the region where the Dugongidae originated in the mid-late Eocene, along with Caribbean Sea. Dugongs are long lived, and the oldest recorded specimen reached age 73. They have few natural predators, although animals such as crocodiles, killer whales, and sharks pose a threat to the young, and a dugong has also


title: Dugong content: been recorded to have died from trauma after being impaled by a stingray barb. A large number of infections and parasitic diseases affect dugongs. Detected pathogens include helminths, cryptosporidium, different types of bacterial infections, and other unidentified parasites. 30% of dugong deaths in Queensland since 1996 are thought to be because of disease. Although they are social animals, they are usually solitary or found in pairs due to the inability of seagrass beds to support large populations. Gatherings of hundreds of dugongs sometimes happen, but they last only for a short time. Because they are shy, and do not approach


title: Dugong content: humans, little is known about dugong behaviour. They can go six minutes without breathing (though about two and a half minutes is more typical), and have been known to rest on their tail to breathe with their heads above water. They can dive to a maximum depth of ; they spend most of their lives no deeper than . Communication between individuals is through chirps, whistles, barks, and other sounds that echo underwater. Different sounds have been observed with different amplitudes and frequencies, implying different purposes. Visual communication is limited due to poor eyesight, and is mainly used for activities


title: Dugong content: such as lekking for courtship purposes. Mothers and calves are in almost constant physical contact, and calves have been known to reach out and touch their mothers with their flippers for reassurance. Dugongs are semi-nomadic, often travelling long distances in search of food, but staying within a certain range their entire life. Large numbers often move together from one area to another. It is thought that these movements are caused by changes in seagrass availability. Their memory allows them to return to specific points after long travels. Dugong movements mostly occur within a localised area of seagrass beds, and animals


title: Dugong content: in the same region show individualistic patterns of movement. Daily movement is affected by the tides. In areas where there is a large tidal range, dugongs travel with the tide in order to access shallower feeding areas. In Moreton Bay, dugongs often travel between foraging grounds inside the bay and warmer oceanic waters. At higher latitudes dugongs make seasonal travels to reach warmer water during the winter. Occasionally individual dugongs make long-distance travels over many days, and can travel over deep ocean waters. One animal was seen as far south as Sydney. Although they are marine creatures, dugongs have been


title: Dugong content: known to travel up creeks, and in one case a dugong was caught up a creek near Cooktown. Dugongs, along with other sirenians, are referred to as "sea cows" because their diet consists mainly of sea-grass. When eating they ingest the whole plant, including the roots, although when this is impossible they will feed on just the leaves. A wide variety of seagrass has been found in dugong stomach contents, and evidence exists they will eat algae when seagrass is scarce. Although almost completely herbivorous, they will occasionally eat invertebrates such as jellyfish, sea squirts, and shellfish. Dugongs in Moreton


title: Dugong content: Bay, Australia, are omnivorous, feeding on invertebrates such as polychaetes or marine algae when the supply of their choice grasses decreases. In other southern areas of both western and eastern Australia, there is evidence that dugongs actively seek out large invertebrates. This does not apply to dugongs in tropical areas, in which faecal evidence indicates that invertebrates are not eaten. Most dugongs do not feed from lush areas, but where the seagrass is more sparse. Additional factors such as protein concentration and regenerative ability also affect the value of a seagrass bed. The chemical structure and composition of the seagrass


title: Dugong content: is important, and the grass species most often eaten are low in fibre, high in nitrogen, and easily digestible. In the Great Barrier Reef, dugongs feed on low-fibre high-nitrogen seagrass such as "Halophila" and "Halodule", so as to maximize nutrient intake instead of bulk eating. Seagrasses of a lower seral are preferred, where the area has not fully vegetated. Only certain seagrass meadows are suitable for dugong consumption, due to the dugong's highly specialised diet. There is evidence that dugongs actively alter seagrass species compositions at local levels. Dugongs may search out deeper seagrass. Feeding trails have been observed as


title: Dugong content: deep as , and dugongs have been seen feeding as deep as . Dugongs are relatively slow moving, swimming at around . When moving along the seabed to feed they walk on their pectoral fins. Dugong feeding may favor the subsequent growth low-fibre, high-nitrogen seagrasses such as "Halophilia" and "Halodule." Species such as "Zosteria capricorni" are more dominant in established seagrass beds, but grow slowly, while "Halophilia" and "Halodule" grow quickly in the open space left by dugong feeding. This behavior is known as cultivation grazing, and favors the rapidly growing, higher nutrient seagrasses that dugongs prefer. Dugongs may also


title: Dugong content: prefer to feed on younger, less fibrous strands of seagrasses, and cycles of cultivation feeding at different seagrass meadows may provide them with a greater number of younger plants. Due to their poor eyesight, dugongs often use smell to locate edible plants. They also have a strong tactile sense, and feel their surroundings with their long sensitive bristles. They will dig up an entire plant and then shake it to remove the sand before eating it. They have been known to collect a pile of plants in one area before eating them. The flexible and muscular upper lip is used


title: Dugong content: to dig out the plants. This leaves furrows in the sand in their path. A dugong reaches sexual maturity between the ages of eight and eighteen, older than in most other mammals. The way that females know how a male has reached sexual maturity is by the eruption of tusks in the male since tusks erupt in males when testosterone levels reach a high enough level. The age when a female first gives birth is disputed, with some studies placing the age between ten and seventeen years, while others place it as early as six years. There is evidence that


title: Dugong content: male dugongs lose fertility at older ages. Despite the longevity of the dugong, which may live for 50 years or more, females give birth only a few times during their life, and invest considerable parental care in their young. The time between births is unclear, with estimates ranging from 2.4 to 7 years. Mating behaviour varies between populations located in different areas. In some populations, males will establish a territory which females in heat will visit. In these areas a male will try to impress the females while defending the area from other males, a practice known as lekking. In


title: Dugong content: other areas many males will attempt to mate with the same female, sometimes inflicting injuries to the female or each other. During this the female will have copulated with multiple males, who will have fought to mount her from below. This greatly increases the chances of conception. Females give birth after a 13–15 month gestation, usually to just one calf. Birth occurs in very shallow water, with occasions known where the mothers were almost on the shore. As soon as the young is born the mother pushes it to the surface to take a breath. Newborns are already long and


title: Dugong content: weigh around . Once born, they stay close to their mothers, possibly to make swimming easier. The calf nurses for 14–18 months, although it begins to eat seagrasses soon after birth. A calf will only leave its mother once it has matured. Dugongs have historically provided easy targets for hunters, who killed them for their meat, oil, skin, and bones. As the anthropologist A. Asbjørn Jøn has noted, they are often considered as the inspiration for mermaids, and people around the world developed cultures around dugong hunting. In some areas it remains an animal of great significance, and a growing


title: Dugong content: ecotourism industry around dugongs has had economic benefit in some countries. There is a 5,000-year-old wall painting of a dugong, apparently drawn by neolithic peoples, in Tambun Cave, Ipoh, Malaysia. This was discovered by Lieutenant R.L Rawlings in 1959 while on a routine patrol. During the Renaissance and the Baroque eras, dugongs were often exhibited in wunderkammers. They were also presented as Fiji mermaids in sideshows. Dugong meat and oil have traditionally been some of the most valuable foods of Australian aborigines and Torres Strait Islanders. Some aborigines regard dugongs as part of their Aboriginality. Dugongs have also played a


title: Dugong content: role in legends in Kenya, and the animal is known there as the "Queen of the Sea". Body parts are used as food, medicine, and decorations. In the Gulf states, dugongs served not only as a source of food, but their tusks were used as sword handles. Dugong oil is important as a preservative and conditioner for wooden boats to people in around the Gulf of Kutch in India, who also believe the meat to be an aphrodisiac. Dugong ribs were used to make carvings in Japan. In Southern China dugongs were traditionally regarded as a "miraculous fish", and it


title: Dugong content: was bad luck to catch them. A wave of immigration beginning at the end of the 1950s resulted in dugongs being hunted for food. In the Philippines, dugongs are thought to bring bad luck, and parts of them are used to ward against evil spirits. In areas of Thailand it is believed that the dugong's tears form a powerful love potion, while in parts of Indonesia they are considered reincarnations of women. In Papua New Guinea they are seen as a symbol of strength. Dugongs' or sea cows' hides have been thought to have been used as coverings in the


title: Dugong content: building of the Old Testament portable worship tent known as the Tabernacle. Dugong numbers have decreased in recent times. For a population to remain stable, 95 per cent of adults must survive the span of one year. The estimated percentage of females humans can kill without depleting the population is 1–2%. This number is reduced in areas where calving is minimal due to food shortages. Even in the best conditions a population is unlikely to increase more than 5% a year, leaving dugongs vulnerable to over-exploitation. The fact that they live in shallow waters puts them under great pressure from


title: Dugong content: human activity. Research on dugongs and the effects of human activity on them has been limited, mostly taking place in Australia. In many countries, dugong numbers have never been surveyed. As such, trends are uncertain, with more data needed for comprehensive management. The only data stretching back far enough to mention population trends comes from the urban coast of Queensland, Australia. The last major worldwide study, made in 2002, concluded that the dugong was declining and possibly extinct in a third of its range, with unknown status in another half. The IUCN Red List lists the dugong as vulnerable, and


title: Dugong content: the Convention on International Trade in Endangered Species of Wild Fauna and Flora regulates and in some areas has banned international trade. Regional cooperation is important due to the widespread distribution of the animal, and in 1998 there was strong support for Southeast Asian cooperation to protect dugongs. Kenya has passed legislation banning the hunting of dugongs and restricting trawling, but the dugong is not yet listed under Kenya's Wildlife Act for endangered species. Mozambique has had legislation to protect dugongs since 1955, but this has not been effectively enforced. Many marine parks have been established on the African coast


title: Dugong content: of the Red Sea, and the Egyptian Gulf of Aqaba is fully protected. The United Arab Emirates has banned all hunting of dugongs within its waters, as has Bahrain. The UAE has additionally banned drift net fishing. India and Sri Lanka ban the hunting and selling of dugongs and their products. Japan has listed dugongs as endangered and has banned intentional kills and harassment. Hunting, catching, and harassment is banned by the People's Republic of China. The first marine mammal to be protected in the Philippines was the dugong, although monitoring this is difficult. Palau has legislated to protect dugongs,


title: Dugong content: although this is not well enforced and poaching persists. Indonesia lists dugongs as a protected species, however protection is not always enforced and souvenir products made from dugong parts can be openly found in markets in Bali. The dugong is a national animal of Papua New Guinea, which bans all except traditional hunting. Vanuatu and New Caledonia ban hunting of dugongs. Dugongs are protected throughout Australia, although the rules vary by state; in some areas indigenous hunting is allowed. Dugongs are listed under the Nature Conservation Act in the Australian state of Queensland as vulnerable. Most currently live in established


title: Dugong content: marine parks, where boats must travel at a restricted speed and mesh net fishing is restricted. In Vietnam, an illegal network targeting dugongs had been detected and was shut down in 2012. Potential hunts along Tanzanian coasts by fishermen have raised concerns as well. Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include hunting, habitat degradation, and fishing-related fatalities. Entanglement in fishing nets has caused many deaths, although there are no precise statistics. Most issues with industrial fishing occur in deeper waters where dugong populations are low, with local fishing being the


title: Dugong content: main risk in shallower waters. As dugongs cannot stay underwater for a very long period, they are highly prone to deaths due to entanglement. The use of shark nets has historically caused large numbers of deaths, and they have been eliminated in most areas and replaced with baited hooks. Hunting has historically been a problem too, although in most areas they are no longer hunted, with the exception of certain indigenous communities. In areas such as northern Australia, hunting remains the greatest impact on the dugong population. Vessel strikes have proved a problem for manatees, but the relevance of this


title: Dugong content: to dugongs is unknown. Increasing boat traffic has increased danger, especially in shallow waters. Ecotourism has increased in some countries, although effects remain undocumented. It has been seen to cause issues in areas such as Hainan due to environmental degradation. Modern farming practise and increased land clearing have also had an impact, and much of the coastline of dugong habitats is undergoing industrialisation, with increasing human populations. Dugongs accumulate heavy metal ions in their tissues throughout their lives, more so than other marine mammals. The effects are unknown. While international cooperation to form a conservative unit has been undertaken, socio-political


title: Dugong content: needs are an impediment to dugong conservation in many developing countries. The shallow waters are often used as a source of food and income, problems exacerbated by aid used to improve fishing. In many countries, legislation does not exist to protect dugongs, and if it does it is not enforced. Oil spills are a danger to dugongs in some areas, as is land reclamation. In Okinawa the small dugong population is threatened by United States military activity. Plans exist to build a military base close to the Henoko reef, and military activity also adds the threats of noise pollution, chemical


title: Dugong content: pollution, soil erosion, and exposure to depleted uranium. The military base plans have been fought in US courts by some Okinawans, whose concerns include the impact on the local environment and dugong habitats. It was later revealed that the government of Japan was hiding evidence of the negative effects of ship lanes and human activities on dugongs observed during surveys carried out off Henoko reef. One of the three individuals has not been observed since June 2015, corresponding to the start of the excavation operations. If dugongs do not get enough to eat they may calve later and produce fewer


title: Dugong content: young. Food shortages can be caused by many factors, such as a loss of habitat, death and decline in quality of seagrass, and a disturbance of feeding caused by human activity. Sewage, detergents, heavy metal, hypersaline water, herbicides, and other waste products all negatively affect seagrass meadows. Human activity such as mining, trawling, dredging, land reclamation, and boat propeller scarring also cause an increase in sedimentation which smothers seagrass and prevents light from reaching it. This is the most significant negative factor affecting seagrass. "Halophila ovalis"—one of the dugong's preferred species of seagrass—declines rapidly due to lack of light, dying


title: Dugong content: completely after 30 days. Extreme weather such as cyclones and floods can destroy hundreds of square kilometres of seagrass meadows, as well as washing dugongs ashore. The recovery of seagrass meadows and the spread of seagrass into new areas, or areas where it has been destroyed, can take over a decade. Most measures for protection involve restricting activities such as trawling in areas containing seagrass meadows, with little to no action on pollutants originating from land. In some areas water salinity is increased due to wastewater, and it is unknown how much salinity seagrass can withstand. Dugong habitat in the


title: Dugong content: Oura Bay area of Henoko, Okinawa, Japan, is currently under threat from land reclamation conducted by Japanese Government in order to build a US Marine base in the area. In August 2014, preliminary drilling surveys were conducted around the seagrass beds there. The construction is expected to seriously damage the dugong population's habitat, possibly leading to local extinction. The Australian state of Queensland has sixteen dugong protection parks, and some preservation zones have been established where even Aboriginal Peoples are not allowed to hunt. Capturing animals for research has caused only one or two deaths; dugongs are expensive to keep


title: Dugong content: in captivity due to the long time mothers and calves spend together, and the inability to grow the seagrass that dugongs eat in an aquarium. Only one orphaned calf has ever been successfully kept in captivity. Worldwide, only three dugongs are held in captivity. A female from the Philippines lives at Toba Aquarium in Toba, Mie, Japan. A male also lived there until he died on 10 February 2011. The second resides in Sea World Indonesia, after having been rescued from a fisherman's net and treated. The last one, a male, is kept at Sydney Aquarium, where he has resided


title: Dugong content: since he was a juvenile. Sydney Aquarium had a second dugong for many years, until she died in 2018. Gracie, a captive dugong at Underwater World, Singapore, was reported to have died in 2014 at the age of 19, from complications arising from an acute digestive disorder. Dugong The dugong (; "Dugong dugon") is a medium-sized marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow ("Hydrodamalis gigas"), was hunted to extinction


title: "California sea lion" content: California sea lion The California sea lion ("Zalophus californianus") is a coastal eared seal native to western North America. It is one of six species of sea lion. Its natural habitat ranges from southeast Alaska to central Mexico, including the Gulf of California. Sea lions are sexually dimorphic; males are larger than females, and have a thicker neck, and protruding sagittal crest. They mainly haul-out on sandy or rocky beaches, but they also frequent manmade environments such as marinas and wharves. Sea lions feed on a number of species of fish and squid, and are preyed on by orcas and


title: "California sea lion" content: 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. Sea lions communicate with numerous vocalizations, notably with barks and mother-pup contact calls. Outside their breeding season, sea lions spend much of their time at sea, but they come to shore to molt. Sea lions are particularly intelligent, can be trained to perform various tasks and display limited fear of humans if


title: "California sea lion" content: accustomed to them. Because of this, California sea lions are a popular choice for public display in zoos, circuses and oceanariums, and are trained by the United States Navy for certain military operations. The International Union for Conservation of Nature (IUCN) lists the species as Least Concern due to its abundance. Predation by California sea lions on threatened or endangered salmon species at Bonneville Dam has resulted in more than 50 of them being killed by state officials. The California sea lion was described by René Primevère Lesson, a French naturalist, in 1828. It is grouped with other sea lions


title: "California sea lion" content: and fur seals in the family Otariidae. Otariids, also known as eared seals, differ from true seals in having external ear flaps, and proportionately larger foreflippers and pectoral muscles. Along with the Galapagos sea lion and the extinct Japanese sea lion, the California sea lion belongs to the genus "Zalophus", which derives from the Greek words "za", meaning "intensive," and "lophus," meaning "crest." This refers to the protruding sagittal crest of the males, which distinguishes members of the genus. Traditionally, the Galapagos sea lion and Japanese sea lion were classified as subspecies of the California sea lion. However, a genetic


title: "California sea lion" content: study in 2007 found that all three are in fact separate species. The lineages of the California and Japanese sea lion appear to have split off 2.2 million years ago during the Pliocene. The California sea lion differs from the Galapagos sea lion in its greater sexual dimorphism. The Steller sea lion is the closest extant relative of the "Zalophus" sea lions, being a sister taxon. Being sexually dimorphic, California sea lions differ in size, shape, and coloration between the sexes. Males are typically around long and weigh up to , while females are typically around and weigh up to


title: "California sea lion" content: . Females and juveniles have a tawny brown pelage, although they may be temporarily light gray or silver after molting. The pelage of adult males can be anywhere from light brown to black, but is typically dark brown. The face of adult males may also be light tan in some areas. Pups have a black or dark brown pelage at birth. Although the species has a slender build, adult males have robust necks, chests, and shoulders. Adult males also have a protruding crest which gives them a "high, domed forehead"; it is tufted with white hairs. They also have manes,


title: "California sea lion" content: which are less developed than those of adult male South American and Steller sea lions. Both sexes have long, narrow muzzles. 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. The flexibility of its spine allows the 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. When moving on


title: "California sea lion" content: land, the 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. Sea lions may travel at speeds of around , and can dive at depths of and for up to 9.9 minutes, though most dives are typically and last less than 3 minutes. Sea lions have color vision, though it is limited to the blue-green area of the color spectrum. This is likely an adaptation


title: "California sea lion" content: for living in marine coastal habitats. Sea lions have fairly acute underwater hearing, with a hearing range of 0.4–32 kHz. 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. The California sea lion ranges along the western coast and islands of North America, from southeast Alaska to central Mexico. Mitochondrial DNA sequences in 2009 have identified five distinct California sea lion populations: the U.S. or Pacific


title: "California sea lion" content: Temperate stock, the Western Baja California or Pacific Tropical stock, and the Southern, Central, and Northern Gulf of California stocks. The U.S. stock breeds mainly in the Channel Islands, although some breeding sites may be established in northern California, and females are now commonly found there. The Western Baja California stock mainly breeds near Punta Eugenia and at Isla Santa Margarita. The above-mentioned stocks are separated by the Ensenada Front. The stocks of the Gulf of California live in the shallow waters of the north (Northern stock), the tidal islands near the center (Central stock), and the mouth of the


title: "California sea lion" content: bay (Southern stock). The stock status of the sea lions at the deep waters of the central bay has not been analyzed. Vagrants can reach western north pacific such as on Commander Islands. Although several otariinae have been recorded around Japanese archipelago in recent years, their exact origins are unclear. During the breeding season, 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. Non-breeding individuals may gather at marinas, wharves, or even navigational buoys. California sea lions


title: "California sea lion" content: can also live in fresh water for periods of time, such as near Bonneville Dam, nearly 150 miles up the Columbia River. In 2004 a healthy sea lion was found sitting on a road in Merced County, California, almost a hundred miles upstream from the San Francisco Bay and half a mile from the San Joaquin River. California sea lions feed on a wide variety of seafood, mainly squid and fish, and sometimes clams. Commonly eaten fish and squid species include salmon, hake, Pacific whiting, anchovy, herring, rockfish, lamprey, dogfish, and market squid. They mostly forage near mainland coastlines, the


title: "California sea lion" content: continental shelf, and seamounts. They may also search along the ocean bottom. California sea lions may eat alone or in small to large groups, depending on the amount of food available. They sometimes cooperate with other predators, such as dolphins, porpoises, and seabirds, when hunting large schools of fish. Sea lions sometimes follow dolphins and exploit their hunting efforts. Adult females feed between from shore. Males may forage as far as from shore when water temperatures rise. They also have learned to feed on steelhead and salmon below fish ladders at Bonneville Dam and at other locations where fish must


title: "California sea lion" content: queue in order to pass through dams and locks that block their passage. Sea lions are preyed on by killer whales and large sharks. At Monterey Bay, California sea lions appear to be the more common food items for transient mammal-eating killer whale pods. The sea lions may respond to the dorsal fin of a killer whale and remain vigilant, even when encountering resident fish-eating pods. Sea lions are also common prey for white sharks. They have been found with scars made by attacks from both white sharks and shortfin mako sharks. Sharks attack sea lions by ambushing them while


title: "California sea lion" content: they are resting at the surface. Sea lions that are attacked in the hindquarters are more likely to survive and make it to the shore. California sea lions breed gregariously between May and August, when they arrive at their breeding rookeries. When establishing a territory, the males will try to increase their chances of reproducing by staying on the rookery for as long as possible. During this time, they will fast, relying on a thick layer of fat called blubber for energy. Size and patience allow a male to defend his territory more effectively; the bigger the male, the more


title: "California sea lion" content: blubber he can store and the longer he can wait. A male sea lion usually keeps his territory for around 27 days. Females have long parturition intervals, and thus the males do not establish their territories until after the females give birth. Most fights occur during this time. After this, the males rely on ritualized displays (vocalizations, head-shaking, stares, bluff lunges, and so on) to maintain their territorial boundaries. Since temperatures can reach over during this time, males must include water within their territories. Some territories are underwater, particularly those near steep cliffs. Sea lions that fail to establish a


title: "California sea lion" content: territory are driven out to sea or gather at a nearby beach. 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. The territorial and mating system of the California sea lion has been described as similar to a lek system, as females appear to choose their mates while moving though different territories. They avoid males that are too aggressive or energetic. Males are usually unable to prevent females from leaving their territories, particularly


title: "California sea lion" content: in water. Mating may occur outside the rookeries, between non-territorial males and females, as the latter move to and from the mating site. In some rookeries, copulation may be monopolized by a few males, while at others, a single male may sire no more than four pups. 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


title: "California sea lion" content: sea lions in the Gulf of California. Females remain with their pups on shore 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 on shore tend to gather in nurseries to socialize and play. 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


title: "California sea lion" content: efforts of the mothers. However, as pups get older, they get more involved in reunions. Older pups may sometimes join their mothers during their foraging trips. 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. Pups are weaned by a year but can continue to suckle for another year. California sea lions communicate with a range of vocalizations. The most commonly used one is their characteristic bark. Territorial males are the


title: "California sea lion" content: loudest and most continuous callers, and barks are produced constantly during the peak of the breeding season. Sea lions bark especially rapidly when excited. The barks of territorial and non-territorial males sound similar, although those of the former are deeper. Males may bark when threatening other males or during courtship. The only other vocalization made by territorial males is a "prolonged hoarse grunt sound" made when an individual is startled by a human. This vocalization is also made by groups of non-reproductive males. Female sea lions are less vocal. Their barks, high-pitched and shorter than those made by males, are


title: "California sea lion" content: used in aggressive situations. Other aggressive vocalizations given by females include the "squeal", the "belch", and the "growl". The sound a female 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. California sea lions can produce vocalizations underwater. These include "whinny" sounds, barks, buzzings, and clicks. Outside the breeding season, males migrate to the northern ends of the species range to feed, while females forage near the breeding rookeries. Sea


title: "California sea lion" content: lions can stay at sea for as long as two weeks at a time. They make continuous dives, returning to the surface to rest. 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. Gulf of California sea lions do not migrate; they stay in the Gulf year-round. Marine biologist Ronald J. Schusterman and his research associates have studied sea lions' cognitive ability. They have discovered that sea lions are able to recognize relationships between stimuli based


title: "California sea lion" content: on similar functions or connections made with their peers, rather than only the stimuli's common features. Sea lions have demonstrated the ability to understand simple syntax and commands when taught an artificial sign language. However, the sea lions rarely used the signs semantically or logically. In 2011, a California sea lion named "Ronan" was recorded bobbing her head in synchronization to musical rhythms. This "rhythmic entrainment" was previously seen only in humans, parrots and other birds possessing vocal mimicry. Because of their intelligence and trainability, California sea lions have been used by circuses and marine mammal parks to perform various


title: "California sea lion" content: 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 sea lion so it may accidentally balance it or hold the ball on its nose, thereby gaining an understanding of what to do. A 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. Some organizations, such as the


title: "California sea lion" content: Humane Society of the United States and World Animal Protection, object to using 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. Less entertainment-oriented zoos may still encourage animal play by throwing fish at animals in different directions and providing play equipment. The California sea lion is used in military applications by the U.S. Navy Marine Mammal Program, including detecting naval mines and enemy divers. In the Persian Gulf, the animals can swim behind divers approaching a US naval ship and attach


title: "California sea lion" content: a clamp with a rope to the diver's leg. Navy officials say the sea lions can do this in seconds, before the enemy realizes what happened. Organizations like PETA believe that such operations put the animals in danger. However, the Navy insists that the sea lions are removed once their mission is complete. The IUCN lists the California sea lion as Least Concern due to "its large and increasing population size." The estimated population is 238,000–241,000 for the U.S. or Pacific Temperate stock, 75,000–85,000 for the Western Baja California or Pacific Tropical stock, and 31,393 for the population in the


title: "California sea lion" content: Gulf of California. Off the Pacific coast of the United States, sea lions are so numerous that they are close to carrying capacity, while the Gulf of California population declined by 20% by 2008. Sea lions may be killed when in conflict with fishermen, by poaching, and by entanglements in man-made garbage. They are also threatened by pollutants like DDT and PCB which accumulate in the marine food chain. In the United States, the California sea lion is protected on the federal Marine Mammal Protection Act (MMPA), passed in 1972, which outlaws hunting, killing, capture, and harassment of the animal.


title: "California sea lion" content: In 1994 an amendment to the Act allowed for the possibility of limited lethal removal of pinnipeds preying on endangered salmonids should the level of predation be documented to have a significant adverse impact on the decline or recovery of ESA-listed salmonids. Applications have been granted for removal of several individual sea lions at Ballard Locks and at the Bonneville Dam, where up to 92 sea lions can be killed each year for a 5-year period. Critics have objected to the killing of the sea lions, pointing out that the level of mortality permitted as a result of recreational and


title: "California sea lion" content: commercial fisheries in the river and as part of the operation of hydroelectric dams pose a greater threat to the salmon. These animals exploit more man-made environments like docks for haul-out sites. Many docks are not designed to withstand the weight of several resting 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. In January and February 2015, 1450 malnourished or sick sea lion pups were found along stretches of the California coast, and estimations give a


title: "California sea lion" content: higher number of dead pups. The National Oceanic and Atmospheric Administration has pointed to unprecedentedly warm Pacific coastal waters, related to Pacific decadal oscillation and El Niño, as the likely cause. Elevated water temperatures reduced the abundance of anchovies, sardines and mackerel, principal components of the sea lion pup diet during nursery season. This caused many sea lion pups to starve, while others died when they took to open waters in search of food at too early an age . Several months earlier, in the Summer of 2014, a large number of Cassin's auklet chicks died during the fledging period


title: "California sea lion" content: due to similar circumstances brought about by elevated water temperatures. California sea lion The California sea lion ("Zalophus californianus") is a coastal eared seal native to western North America. It is one of six species of sea lion. Its natural habitat ranges from southeast Alaska to central Mexico, including the Gulf of California. Sea lions are sexually dimorphic; males are larger than females, and have a thicker neck, and protruding sagittal crest. They mainly haul-out on sandy or rocky beaches, but they also frequent manmade environments such as marinas and wharves. Sea lions feed on a number of species of


title: Pinniped content: 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


title: Pinniped content: closest living relatives are bears and musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago. Seals range in size from the and Baikal seal to the and 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


title: Pinniped content: 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


title: Pinniped content: 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


title: Pinniped content: 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,


title: Pinniped content: 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


title: Pinniped content: 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. The German naturalist Johann Karl Wilhelm Illiger was the first to recognize the pinnipeds as a distinct taxonomic unit; in 1811 he gave the name Pinnipedia to both a family and an order. American zoologist Joel Asaph Allen reviewed the world's pinnipeds in an 1880 monograph, "History of North American pinnipeds, a monograph of the walruses, sea-lions, sea-bears and seals of North America". In this publication, he traced the


title: Pinniped content: history of names, gave keys to families and genera, described North American species and provided synopses of species in other parts of the world. In 1989, Annalisa Berta and colleagues proposed the unranked clade Pinnipedimorpha to contain the fossil genus "Enaliarctos" and modern seals as a sister group. Pinnipeds belong to the order Carnivora and the suborder Caniformia (known as dog-like carnivorans). Pinnipedia was historically considered its own suborder under Carnivora. Of the three extant families, the Otariidae and Odobenidae are grouped in the superfamily Otarioidea, while the Phocidae belong to the superfamily Phocoidea. Otariids are also known as eared


title: Pinniped content: seals due to the presence of pinnae. These animals rely on their well-developed fore-flippers to propel themselves through the water. They can also turn their hind-flippers forward and "walk" on land. The anterior end of an otariid's frontal bones extends between the nasal bones, and the supraorbital foramen is large and flat horizontally. The supraspinatous fossas are divided by a "secondary spine" and the bronchi are divided anteriorly. Otariids consist of two types: sea lions and fur seals. Sea lions are distinguished by their rounder snouts and shorter, rougher pelage, while fur seals have more pointed snouts, longer fore-flippers and


title: Pinniped content: thicker fur coats that include an undercoat and guard hairs. The former also tend to be larger than the latter. Five genera and seven species (one now extinct) of sea lion are known to exist, while two genera and nine species of fur seal exist. While sea lions and fur seals have historically been considered separate subfamilies (Otariinae and Arctocephalinae respectively), a 2001 genetic study found that the northern fur seal is more closely related to several sea lion species. This is supported by a 2006 molecular study that also found that the Australian sea lion and New Zealand sea


title: Pinniped content: lion are more closely related to "Arctocephalus" than to other sea lions. Odobenidae consists of only one living member: the modern walrus. This animal is easily distinguished from other extant pinnipeds by its larger size (exceeded only by the elephant seals), nearly hairless skin and long upper canines, known as tusks. Like otariids, walruses are capable of turning their hind-flippers forward and can walk on land. When moving in water, the walrus relies on its hind-flippers for locomotion, while its fore-flippers are used for steering. In addition, the walrus lacks external ear flaps. Walruses have pterygoid bones that are broad


title: Pinniped content: and thick, frontal bones that are V-shaped at the anterior end and calcaneuses with pronounced tuberosity in the middle. Phocids are known as true or "earless" seals. These animals lack external ear flaps and are incapable of turning their hind-flippers forward, which makes them more cumbersome on land. In water, true seals swim by moving their hind-flippers and lower body from side to side. Phocids have thickened mastoids, enlarged entotympanic bones, everted pelvic bones and massive ankle bones. They also lack supraorbital processes on the frontal and have underdeveloped calcaneal tubers. A 2006 molecular study supports the division of phocids


title: Pinniped content: into two monophyletic subfamilies: Monachinae, which consists of "Mirounga", Monachini and Lobodontini; and Phocinae, which includes "Pusa", "Phoca", "Halichoerus", "Histriophoca", "Pagophilus", "Erignathus" and "Cystophora". In a 2012 review of pinniped taxonomy, Berta and Morgan Churchill suggested that, based on morphological and genetic criteria, there are 33 extant species and 29 subspecies of pinnipeds, although five of the latter lack sufficient support to be conclusively considered subspecies. They recommend that the genus "Arctocephalus" be limited to "Arctocephalus pusillus", and they resurrected the name "Arctophoca" for several species and subspecies formerly placed in "Arctocephalus". More than 50 fossil species have been described.


title: Pinniped content: One popular hypothesis suggested that pinnipeds are diphyletic (descended from two ancestral lines), with walruses and otariids sharing a recent common ancestor with bears and phocids sharing one with Musteloidea. However, morphological and molecular evidence support a monophyletic origin. Nevertheless, there is some dispute as to whether pinnipeds are more closely related to bears or musteloids, as some studies support the former theory and others the latter. Pinnipeds split from other caniforms 50 million years ago (mya) during the Eocene. Their evolutionary link to terrestrial mammals was unknown until the 2007 discovery of "Puijila darwini" in early Miocene deposits in


title: Pinniped content: Nunavut, Canada. Like a modern otter, "Puijila" had a long tail, short limbs and webbed feet instead of flippers. However, its limbs and shoulders were more robust and "Puijila" likely had been a quadrupedal swimmer—retaining a form of aquatic locomotion that give rise to the major swimming types employed by modern pinnipeds. The researchers who found "Puijila" placed it in a clade with "Potamotherium" (traditionally considered a mustelid) and "Enaliarctos". Of the three, "Puijila" was the least specialized for aquatic life. The discovery of "Puijila" in a lake deposit suggests that pinniped evolution went through a freshwater transitional phase. "Enaliarctos",


title: Pinniped content: a fossil species of late Oligocene/early Miocene (24–22 Mya) California, closely resembled modern pinnipeds; it was adapted to an aquatic life with a flexible spine, and limbs modified into flippers. Its teeth were adapted for shearing (like terrestrial carnivorans), and it may have stayed near shore more often than its extant relatives. "Enaliarctos" was capable of swimming with both the fore-flippers and hind-flippers, but it may have been more specialized as a fore-flipper swimmer. One species, "Enaliarctos emlongi", exhibited notable sexual dimorphism, suggesting that this physical characteristic may have been an important driver of pinniped evolution. A closer relative of


title: Pinniped content: extant pinnipeds was "Pteronarctos", which lived in Oregon 19–15 mya. As in modern seals, "Pteroarctos" had an orbital wall that was not limited by certain facial bones (like the jugal or lacrimal bone), but was mostly shaped by the maxilla. The ancestors of the Otarioidea and Phocoidea diverged 33 mya. The Phocidae are likely to have descended from the extinct family Desmatophocidae in the North Atlantic. Desmatophocids lived 23–10 Mya and had elongated skulls, fairly large eyes, cheekbones connected by a mortised structure and rounded cheek teeth. They also were sexually dimorphic and may have been capable of propelling themselves


title: Pinniped content: with both the foreflippers and hindflippers. Phocids are known to have existed for at least 15 million years, and molecular evidence supports a divergence of the Monachinae and Phocinae lineages 22 Mya. The fossil monachine "Monotherium" and phocine "Leptophoca" were found in southeastern North America. The deep split between the lineages of "Erignathus" and "Cystophora" 17 Mya suggests that the phocines migrated eastward and northward from the North Atlantic. The genera "Phoca" and "Pusa" could have arisen when a phocine lineage traveled from the Paratethys Sea to the Arctic Basin and subsequently went eastward. The ancestor of the Baikal seal


title: Pinniped content: migrated into Lake Baikal from the Arctic (via the Siberian ice sheet) and became isolated there. The Caspian seal's ancestor became isolated as the Paratethys shrank, leaving the animal in a small remnant sea, the Caspian Sea. The monochines diversified southward. "Monachus" emerged in the Mediterranean and migrated to the Caribbean and then the central North Pacific. The two extant elephant seal species diverged close to 4 mya after the Panamanian isthmus was formed. The lobodontine lineage emerged around 9 mya and colonized the southern ocean in response to glaciation. The lineages of Otariidae and Odobenidae split almost 28 Mya.


title: Pinniped content: Otariids originated in the North Pacific. The earliest fossil "Pithanotaria", found in California, is dated to 11 mya. The "Callorhinus" lineage split earlier at 16 mya. "Zalophus", "Eumetopias" and "Otaria" diverged next, with the latter colonizing the coast of South America. Most of the other otariids diversified in the Southern Hemisphere. The earliest fossils of Odobenidae—"Prototaria" of Japan and "Proneotherium" of Oregon—date to 18–16 Mya. These primitive walruses had much shorter canines and lived on a fish diet rather than a specialized mollusk diet like the modern walrus. Odobenids further diversified in the middle and late Miocene. Several species had


title: Pinniped content: enlarged upper and lower canines. The genera "Valenictus" and "Odobenus" developed elongated tusks. The lineage of the modern walrus may have spread from the North Pacific to the Caribbean (via the Central American Seaway) 8–5 Mya and subsequently made it to the North Atlantic and returned to the North Pacific via the Arctic 1 mya. Alternatively, this lineage may have spread from the North Pacific to the Arctic and subsequently the North Atlantic during the Pleistocene. Pinnipeds have streamlined, spindle-shaped bodies with reduced or non-existent external ear flaps, rounded heads, flexible necks, limbs modified into flippers, and small tails. Pinniped


title: Pinniped content: skulls have large eye orbits, short snouts and a constricted interorbital region. They are unique among carnivorans in that their orbital walls are significantly shaped by the maxilla and are not limited by certain facial bones. Compared to other carnivorans, their teeth tend to be fewer in number (especially incisors and back molars), are pointed and cone-shaped, and lack carnassials. The walrus has unique upper canines that are elongated into tusks. The mammary glands and genitals of pinnipeds can retract into the body. Pinnipeds range in size from the and Baikal seal to the and southern elephant seal. Overall, they


title: Pinniped content: tend to be larger than other carnivorans; the southern elephant seal is the largest carnivoran. Several species have male-biased sexual dimorphism that correlates with the degree of polygyny in a species: highly polygynous species like elephant seals are extremely sexually dimorphic, while less polygynous species have males and females that are closer in size. In lobodontine seals, females are slightly larger than males. Males of sexually dimorphic species also tend to have secondary sex characteristics, such as the prominent proboscis of elephant seals, the inflatable red nasal membrane of hooded seals and the thick necks and manes of otariids. Despite


title: Pinniped content: a correlation between size dimorphism and the degree of polygyny, some evidence suggests that size differences between the sexes originated due to ecological differences and prior to the development of polygyny. Almost all pinnipeds have fur coats, the exception being the walrus, which is only sparsely covered. Even some fully furred species (particularly sea lions) are less haired than most land mammals. In species that live on ice, young pups have thicker coats than adults. The individual hairs on the coat, known collectively as lanugo, can trap heat from sunlight and keep the pup warm. Pinnipeds are typically countershaded, and


title: Pinniped content: are darker colored dorsally and lighter colored ventrally, which serves to eliminate shadows caused by light shining over the ocean water. The pure white fur of harp seal pups conceals them in their Arctic environment. Some species, such as ribbon seals, ringed seals and leopard seals, have patterns of contrasting light and dark coloration. All fully furred species molt; phocids molt once a year, while otariids gradually molt all year. Seals have a layer of subcutaneous fat known as blubber that is particularly thick in phocids and walruses. Blubber serves both to keep the animals warm and to provide energy


title: Pinniped content: and nourishment when they are fasting. It can constitute as much as 50% of a pinniped's body weight. Pups are born with only a thin layer of blubber, but some species compensate for this with thick lanugos. Pinnipeds have a simple stomach that is similar in structure to terrestrial carnivores. Most species have neither a cecum nor a clear demarcation between the small and large intestines; the large intestine is comparatively short and only slightly wider than the latter. Small intestine lengths range from 8 times (California sea lion) to 25 times (elephant seal) the body length. The length of


title: Pinniped content: the intestine may be an adaptation to frequent deep diving, as the increased volume of the digestive tract serves as an extended storage compartment for partially digested food during submersion. Pinnipeds do not have an appendix. As in most marine mammals, the kidneys are divided into small lobes and can effectively absorb water and filter out excess salt. Pinnipeds have two pairs of flippers on the front and back, the fore-flippers and hind-flippers. The elbows and ankles are enclosed within the body. Pinnipeds tend to be slower swimmers than cetaceans, typically cruising at compared to around for several species of


title: Pinniped content: dolphin. Seals are more agile and flexible, and some otariids, such as the California sea lion, are capable of bending their necks backwards far enough to reach their hind-flippers, allowing them to make dorsal turns. Pinnipeds have several adaptions for reducing drag. In addition to their streamlined bodies, they have smooth networks of muscle bundles in their skin that may increase laminar flow and make it easier for them to slip through water. They also lack arrector pili, so their fur can be streamlined as they swim. When swimming, otariids rely on their fore-flippers for locomotion in a wing-like manner


title: Pinniped content: similar to penguins and sea turtles. Fore-flipper movement is not continuous, and the animal glides between each stroke. Compared to terrestrial carnivorans, the fore-limbs of otariids are reduced in length, which gives the locomotor muscles at the shoulder and elbow joints greater mechanical advantage; the hind-flippers serve as stabilizers. Phocids and walruses swim by moving their hind-flippers and lower body from side to side, while their fore-flippers are mainly used for steering. Some species leap out of the water, which may allow then to travel faster. In addition, sea lions are known to "ride" waves, which probably helps them decrease


title: Pinniped content: their energy usage. Pinnipeds can move around on land, though not as well as terrestrial animals. Otariids and walruses are capable of turning their hind-flippers forward and under the body so they can "walk" on all fours. The fore-flippers move in a transverse, rather than a sagittal fashion. Otariids rely on the movements of their heads and necks more than their hind-flippers during terrestrial locomotion. By swinging their heads and necks, otariids create momentum while they are moving. Sea lions have been recorded climbing up flights of stairs. Phocids are less agile on land. They cannot pull their hind-flippers forward,


title: Pinniped content: and move on land by lunging, bouncing and wiggling while their fore-flippers keep them balanced. Some species use their fore-flippers to pull themselves forward. Terrestrial locomotion is easier for phocids on ice, as they can sled along. The eyes of pinnipeds are relatively large for their size and are positioned near the front of the head. One exception is the walrus, whose smaller eyes are located on the sides of its head. This is because it feeds on immobile bottom dwelling mollusks and hence does not need acute vision. A seal's eye is adapted for seeing both underwater and in


title: Pinniped content: air. The lens is mostly spherical, and much of the retina is equidistant from the lens center. The cornea has a flattened center where refraction is nearly equal in both water and air. Pinnipeds also have very muscular and vascularized irises. The well-developed dilator muscle gives the animals a great range in pupil dilation. When contracted, the pupil is typically pear-shaped, although the bearded seal's is more diagonal. In species that live in shallow water, such as harbor seals and California sea lions, dilation varies little, while the deep-diving elephant seals have much greater variation. On land, pinnipeds are near-sighted


title: Pinniped content: in dim light. This is reduced in bright light, as the retracted pupil reduces the lens and cornea's ability to bend light. They also have a well-developed "tapetum lucidum", a reflecting layer that increases sensitivity by reflecting light back through the rods. This helps them see in low-light conditions. Ice-living seals like the harp seal have corneas that can tolerate high levels of ultraviolet radiation typical of bright, snowy environments. As such, they do not suffer snow blindness. Pinnipeds appear to have limited color vision, as they lack S-cones. Flexible eye movement has been documented in seals. The extraocular muscles


title: Pinniped content: of the walrus are well developed. This and its lack of orbital roof allow it to protrude its eyes and see in both frontal and dorsal directions. Seals release large amounts of mucus to protect their eyes. The corneal epithelium is keratinized and the sclera is thick enough to withstand the pressures of diving. As in many mammals and birds, pinnipeds possess nictitating membranes. The pinniped ear is adapted for hearing underwater, where it can hear sound frequencies at up to 70,000 Hz. In air, hearing is somewhat reduced in pinnipeds compared to many terrestrial mammals. While they are capable


title: Pinniped content: of hearing a wide range of frequencies (e.g. 500 to 32,000 Hz in the northern fur seal, compared to 20 to 20,000 Hz in humans), their airborne hearing sensitivity is weaker overall. One study of three species—the harbor seal, California sea lion and northern elephant seal—found that the sea lion was best adapted for airborne hearing, the harbor seal was equally capable of hearing in air and water, and the elephant seal was better adapted for underwater hearing. Although pinnipeds have a fairly good sense of smell on land, it is useless underwater as their nostrils are closed. Pinnipeds have


title: Pinniped content: well-developed tactile senses. Their mystacial vibrissae have ten times the innervation of terrestrial mammals, allowing them to effectively detect vibrations in the water. These vibrations are generated, for example, when a fish swims through water. Detecting vibrations is useful when the animals are foraging and may add to or even replace vision, particularly in darkness. Harbor seals have been observed following varying paths of another seal that swam ahead several minutes before, similar to a dog following a scent trail, and even to discriminate the species and the size of the fish responsible for the trail. Blind ringed seals have


title: Pinniped content: even been observed successfully hunting on their own in Lake Saimaa, likely relying on their vibrissae to gain sensory information and catch prey. Unlike terrestrial mammals, such as rodents, pinnipeds do not move their vibrissae over an object when examining it but instead extend their moveable whiskers and keep them in the same position. By holding their vibrissae steady, pinnipeds are able to maximize their detection ability. The vibrissae of phocids are undulated and wavy while otariid and walrus vibrissae are smooth. Research is ongoing to determine the function, if any, of these shapes on detection ability. The vibrissa's angle


title: Pinniped content: relative to the flow, not the shape, however, seems to be the most important factor. The vibrissae of some otariids grow quite long—those of the Antarctic fur seal can reach . Walruses have the most vibrissae, at 600–700 individual hairs. These are important for detecting their prey on the muddy sea floor. In addition to foraging, vibrissae may also play a role in navigation; spotted seals appear to use them to detect breathing holes in the ice. Before diving, pinnipeds typically exhale to empty their lungs of half the air and then close their nostrils and throat cartilages to protect


title: Pinniped content: the trachea. Their unique lungs have airways that are highly reinforced with cartilaginous rings and smooth muscle, and alveoli that completely deflate during deeper dives. While terrestrial mammals are generally unable to empty their lungs, pinnipeds can reinflate their lungs even after complete respiratory collapse. The middle ear contains sinuses that probably fill with blood during dives, preventing middle ear squeeze. The heart of a seal is moderately flattened to allow the lungs to deflate. The trachea is flexible enough to collapse under pressure. During deep dives, any remaining air in their bodies is stored in the bronchioles and trachea,


title: Pinniped content: which prevents them from experiencing decompression sickness, oxygen toxicity and nitrogen narcosis. In addition, seals can tolerate large amounts of lactic acid, which reduces skeletal muscle fatigue during intense physical activity. The main adaptations of the pinniped circulatory system for diving are the enlargement and increased complexity of veins to increase their capacity. Retia mirabilia form blocks of tissue on the inner wall of the thoracic cavity and the body periphery. These tissue masses, which contain extensive contorted spirals of arteries and thin-walled veins, act as blood reservoirs that increase oxygen stores for use during diving. As with other diving


title: Pinniped content: mammals, pinnipeds have high amounts of hemoglobin and myoglobin stored in their blood and muscles. This allows them to stay submerged for long periods of time while still having enough oxygen. Deep-diving species such as elephant seals have blood volumes that make up to 20% of their body weight. When diving, they reduce their heart rate and maintain blood flow only to the heart, brain and lungs. To keep their blood pressure stable, phocids have an elastic aorta that dissipates some energy of each heartbeat. Pinnipeds conserve heat with their large and compact body size, insulating blubber and fur, and


title: Pinniped content: high metabolism. In addition, the blood vessels in their flippers are adapted for countercurrent exchange. Veins containing cool blood from the body extremities surround arteries, which contain warm blood received from the core of the body. Heat from the arterial blood is transferred to the blood vessels, which then recirculate blood back to the core. The same adaptations that conserve heat while in water tend to inhibit heat loss when out of water. To counteract overheating, many species cool off by flipping sand onto their backs, adding a layer of cool, damp sand that enhances heat loss. The northern fur


title: Pinniped content: seal pants to help stay cool, while monk seals often dig holes in the sand to expose cooler layers to rest in. Pinnipeds spend many months at a time at sea, so they must sleep in the water. Scientists have recorded them sleeping for minutes at a time while slowly drifting downward in a belly-up orientation. Like other marine mammals, seals sleep in water with half of their brain awake so that they can detect and escape from predators. When they are asleep on land, both sides of their brain go into sleep mode. Living pinnipeds mainly inhabit polar and


title: Pinniped content: subpolar regions, particularly the North Atlantic, the North Pacific and the Southern Ocean. They are entirely absent from Indo-Malayan waters. Monk seals and some otariids live in tropical and subtropical waters. Seals usually require cool, nutrient-rich waters with temperatures lower than . Even those that live in warm or tropical climates live in areas that become cold and nutrient rich due to current patterns. Only monk seals live in waters that are not typically cool or rich in nutrients. The Caspian seal and Baikal seal are found in large landlocked bodies of water (the Caspian Sea and Lake Baikal respectively).


title: Pinniped content: As a whole, pinnipeds can be found in a variety of aquatic habitats, including coastal water, open ocean, brackish water and even freshwater lakes and rivers. Most species inhabit coastal areas, though some travel offshore and feed in deep waters off oceanic islands. The Baikal seal is the only freshwater species, though some ringed seals live in freshwater lakes in Russia close to the Baltic sea. In addition, harbor seals may visit estuaries, lakes and rivers and sometimes stay as long as a year. Other species known to enter freshwater include California sea lions and South American sea lions. Pinnipeds


title: Pinniped content: also use a number of terrestrial habitats and substrates, both continental and island. In temperate and tropical areas, they haul out on to sandy and pebble beaches, rocky shores, shoals, mud flats, tide pools and in sea caves. Some species also rest on man-made structures, like piers, jetties, buoys and oil platforms. Pinnipeds may move further inland and rest in sand dunes or vegetation, and may even climb cliffs. Polar-living species haul out on to both fast ice and drift ice. Pinnipeds have an amphibious lifestyle; they spend most of their lives in the water, but haul out to mate,


title: Pinniped content: raise young, molt, rest, thermoregulate or escape from aquatic predators. Several species are known to migrate vast distances, particularly in response to extreme environmental changes, like El Niño or changes in ice cover. Elephant seals stay at sea 8–10 months a year and migrate between breeding and molting sites. The northern elephant seal has one of the longest recorded migration distances for a mammal, at . Phocids tend to migrate more than otariids. Traveling seals may use various features of their environment to reach their destination including geomagnetic fields, water and wind currents, the position of the sun and moon


title: Pinniped content: and the taste and temperature of the water. Pinnipeds may dive during foraging or to avoid predators. When foraging, Weddell seals typically dive for less than 15 minutes to depths of around but can dive for as long as 73 minutes and to depths of up to . Northern elephant seals commonly dive for as long as 20 minutes. They can also dive and for as long as 62 minutes. The dives of otariids tend to be shorter and less deep. They typically last 5–7 minutes with average depths to . However, the New Zealand sea lion has been recorded


title: Pinniped content: diving to a maximum of and a duration of 12 minutes. Walruses do not often dive very deep, as they feed in shallow water. Pinnipeds have lifespans averaging 25–30 years. Females usually live longer, as males tend to fight and often die before reaching maturity. The longest recorded lifespans include 43 years for a wild female ringed seal and 46 years for a wild female grey seal. The age at which a pinniped sexually matures can vary from 2–12 years depending on the species. Females typically mature earlier than males. All pinnipeds are carnivorous and predatory. As a whole, they


title: Pinniped content: mostly feed on fish and cephalopods, followed by crustaceans and bivalves, and then zooplankton and endothermic ("warm-blooded") prey like sea birds. While most species are generalist and opportunistic feeders, a few are specialists. Examples include the crabeater seal, which primarily eats krill, the ringed seal, which eats mainly crustaceans, the Ross seal and southern elephant seal, which specialize on squid, and the bearded seal and walrus, which feed on clams and other bottom-dwelling invertebrates. Pinnipeds may hunt solitarily or cooperatively. The former behavior is typical when hunting non-schooling fish, slow-moving or immobile invertebrates or endothermic prey. Solitary foraging species usually


title: Pinniped content: exploit coastal waters, bays and rivers. An exception to this is the northern elephant seal, which feeds on fish at great depths in the open ocean. In addition, walruses feed solitarily but are often near other walruses in small or large groups that may surface and dive in unison. When large schools of fish or squid are available, pinnipeds such as certain otariids hunt cooperatively in large groups, locating and herding their prey. Some species, such as California and South American sea lions, may forage with cetaceans and sea birds. Seals typically consume their prey underwater where it is swallowed