Pinnipeds

Article

October 25, 2021

Pinnipedia are a widespread group of carnivorous mammals that are adapted to life in the water. Modern taxonomy considers them to be an unclassified plus in the order Carnivora and Caniformia. The pinnipeds include three current families: seals (Phocidae), walruses (Odobenidae; with the only living representative of the ice walrus) and sea lions (Otariidae). The number of pinniped species is around 33-36, depending on whether some taxa are recognized as a separate species or not. More than 50 fossil species are known. Pinnipeds separated from other canines about 50 million years ago, the oldest known ancestors are Enaliarctos and Puijila. Pinnipeds have hydrodynamic bodies with limbs transformed into fins. Walruses and sea lions can slide their hind fins under their bodies, which helps them move on land. They mainly use their front fins to move in the water. Seals cannot push their hind fins under their bodies, so their movement on land is clumsy and slow; in water, however, they are more agile than sea lions. Seals mainly use their hind fins and alternating movements of the back of their body to move in the water. While sea lions have auricles, seals and walruses lack auricles. The size and weight of pinnipeds ranges from about 1.1 m and 55 kg (Baikal seal) to about 6 m and 4 tons (elephant seal). The elephant seal is not only the largest pinniped, but also the largest representative of the order of beasts in the world. The senses of pinnipeds are well developed. Their hearing and sight are perfectly adapted to the water and air environment, and their vibrises allow them to perceive even slight vibrations in the water, which helps them mainly in chasing prey and probably also in navigation. All pinnipeds can dive, some species for more than an hour and to depths of over one kilometer (the elephant seal was even recorded during a dive exceeding 2 kilometers; it can spend up to 2 hours underwater). All pinnipeds have a layer of subcutaneous fat, which serves as thermal insulation. Most species have a body covered with thick hair, only walruses have bare skin on the surface of the body with very sparse hair. Walruses are the only pinnipeds to have long tusks. Although pinnipeds are widespread, most species live in the cold waters of the southern and northern hemispheres. He spends most of his time in the water and comes to land only for the purpose of mating, for litters, raising young, molting or escaping from predators such as sharks and killer whales. They mainly eat invertebrates, fish, cephalopods, and some more aggressive species, such as the leopard seal, also hunt penguins and other pinnipeds. Walruses specialize in collecting bivalves from the ocean floor. Most pinnipeds are polygyny, however, the degree of polygyny depends on the species. Males of pinnipeds that mate on land tend to have more females than species that mate on ice. The largest number of females per male occurs in tusks, where females congregate in numerous harems. Male reproductive strategies vary by species and include the drug system, the defense of specific females from other males, or the defense of specific territories from juices of the same species. The young are born in the spring and summer months and are raised only by females. Females of some species fast during lactation and their young become relatively early (within a few days), while females of other species undertake trips to the sea for food during lactation, and their young take longer to become independent (up to several weeks). Walruses suckle and raise their young at sea. Pinnipeds can make a variety of sounds from loud barking (lac

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