Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species in the order Sirenia: the Amazonian manatee, the West Indian manatee, and the West African manatee. They measure up to 4.0 metres long, weigh as much as 590 kilograms (1,300 lb), and have paddle-like tails.
The Sirenia, commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The extant Sirenia comprise two distinct families: Dugongidae and Trichechidae with a total of four species. The Protosirenidae and Prorastomidae families are extinct. Sirenians are classified in the clade Paenungulata, alongside the elephants and the hyraxes, and evolved in the Eocene 50 million years ago (mya). The Dugongidae diverged from the Trichechidae in the late Eocene or early Oligocene.
Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans, pinnipeds, sirenians, sea otters and polar bears. They are an informal group, unified only by their reliance on marine environments for feeding and survival.
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic group. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.
Placental mammals are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished from monotremes and marsupials in that the fetus is carried in the uterus of its mother to a relatively late stage of development. The name is something of a misnomer considering that marsupials also nourish their fetuses via a placenta, though for a relatively briefer period, giving birth to less developed young which are then nurtured for a period inside the mother's pouch. Placentalia represents the only living group within Eutheria, which contains all mammals more closely related to placentals than to marsupials.
The Desmostylia are an extinct order of aquatic mammals native to the North Pacific from the early Oligocene (Rupelian) to the late Miocene (Tortonian). Desmostylians are the only known extinct order of marine mammals.
Paenungulata is a clade of "sub-ungulates", which groups three extant mammal orders: Proboscidea, Sirenia, and Hyracoidea (hyraxes). At least two more possible orders are known only as fossils, namely Embrithopoda and Desmostylia.
The northern elephant seal is one of two species of elephant seal. It is a member of the family Phocidae. Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating competition. Sexual dimorphism in size is great. Correspondingly, the mating system is highly polygynous; a successful male is able to impregnate up to 50 females in one season.
Elephant seals or sea elephants are very large, oceangoing earless seals in the genus Mirounga. Both species, the northern elephant seal and the southern elephant seal, were hunted to the brink of extinction for oil by the end of the 19th century, but their numbers have since recovered. They are the largest extant carnivorans, weighing up to 4,000 kilograms (8,800 lb). Despite their name, elephant seals are not closely related to elephants, and the large proboscis or trunk that males have was convergently evolved.
Sea Lion Island is the largest of the Sea Lion Island Group of the Falkland Islands. It is 9 km2 (3 sq mi) in area. and lies 14 km (9 mi) southeast of Lafonia. It was designated a Ramsar site on 24 September 2001, and as an Important Bird Area. In 2017 the island was designated as a National Nature Reserve.
The South American fur seal breeds on the coasts of Peru, Chile, the Falkland Islands, Argentina, Uruguay and Brazil. The total population is around 250,000. However, population counts are sparse and outdated. Although Uruguay has long been considered to be the largest population of South American fur seals, recent census data indicates that the largest breeding population of A. a. australis are at the Falkland Islands followed by Uruguay. The population of South American fur seals in 1999 was estimated at 390,000, a drop from a 1987 estimate of 500,000 - however a paucity of population data, combined with inconsistent census methods, makes it difficult to interpret global population trends.
The Amazonian manatee is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It has thin, wrinkled brownish or gray colored skin, with fine hairs scattered over its body and a white chest patch. It is the smallest of the three extant species of manatee.
The West Indian manatee, also known as the North American manatee, is a large, aquatic mammal native to warm coastal areas of the Caribbean, from the eastern United States to northern Brazil. Living alone or in herds, it feeds on underwater plants and uses its whiskers to navigate. It is divided into two subspecies, the Florida manatee in the United States and the Antillean manatee in the Caribbean, both of which are endangered and face pressure from habitat loss, pollution, and other human activity. The West Indian manatee is the largest living member of the sirenians, a group of large aquatic mammals that includes the dugong, other manatees, and the extinct Steller's sea cow.
The web-footed tenrec, Malagasy otter shrew, or aquatic tenrec is the only known semiaquatic tenrec, and is found in eastern Madagascar, especially in and around Ranomafana National Park. It grows to between 25 and 39 cm, and was once thought to be extinct. It feeds on crabs, aquatic insects, and crayfish. The population is considered vulnerable. It was formerly placed in the monotypic genus Limnogale, but has been moved to Microgale based on molecular data showing it to be deeply nested within the latter.
Aquatic and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the European otter. They are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies greatly among species. Among freshwater taxa, the Amazonian manatee and river dolphins are completely aquatic and fully dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests, molts, and breeds on land; and the capybara and hippopotamus which are able to venture in and out of water in search of food.
Sirenia is the order of placental mammals which comprises modern "sea cows" and their extinct relatives. They are the only extant herbivorous marine mammals and the only group of herbivorous mammals to have become completely aquatic. Sirenians are thought to have a 50-million-year-old fossil record. They attained modest diversity during the Oligocene and Miocene, but have since declined as a result of climatic cooling, oceanographic changes, and human interference. Two genera and four species are extant: Trichechus, which includes the three species of manatee that live along the Atlantic coasts and in rivers and coastlines of the Americas and western Africa, and Dugong, which is found in the Indian and Pacific oceans.
Thalassocnus is an extinct genus of semiaquatic ground sloths from the Miocene and Pliocene of the Pacific South American coast. It is monotypic within the subfamily Thalassocninae. The five species—T. antiquus, T. natans, T. littoralis, T. carolomartini, and T. yuacensis—represent a chronospecies, a population gradually adapting to marine life in one direct lineage. They are the only known aquatic sloths, but they may have also been adapted to a terrestrial lifestyle. They have been found in the Pisco Formation of Peru, the Tafna Formation of Argentina, and the Bahía Inglesa, Coquimbo, and Horcón formations of Chile. Thalassocninae has been placed in both the families Megatheriidae and Nothrotheriidae.
The southern elephant seal is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. It gets its name from its massive size and the large proboscis of the adult male, which is used to produce very loud roars, especially during the breeding season. A bull southern elephant seal is about 40% heavier than a male northern elephant seal, which is nearly twice the weight of a male walrus, or 6–7 times heavier than the largest living mostly terrestrial carnivorans, the Kodiak bear and the polar bear.
Hyraxes, also called dassies, are small, stout, herbivorous mammals in the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Modern hyraxes are typically between 30 and 70 cm long and weigh between 2 and 5 kg. They are superficially similar to marmots, or over-large pikas, but are paradoxically much more closely related to elephants and sea cows. Hyraxes have a life span from 9 to 14 years. Both types of 'rock' hyrax live on rock outcrops, including cliffs in Ethiopia and isolated granite outcrops called koppies in southern Africa;
In animal physiology, hydrodynamic reception refers to the ability of some animals to sense water movements generated by biotic or abiotic sources. This form of mechanoreception is useful for orientation, hunting, predator avoidance, and schooling. Frequent encounters with conditions of low visibility can prevent vision from being a reliable information source for navigation and sensing objects or organisms in the environment. Sensing water movements is one resolution to this problem.
