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A stranding is when a cetacean leaves the water to lie on a beach. In some cases, groups of whales strand together. The best known are mass strandings of pilot whales and sperm whales. Stranded cetaceans usually die, because their as much as 90 metric tons (99 short tons) body weight compresses their lungs or breaks their ribs. Smaller whales ...
The family Balaenidae, the right whales, contains two genera and four species. All right whales have no ventral grooves; a distinctive head shape with a strongly arched, narrow rostrum, bowed lower jaw; lower lips that enfold the sides and front of the rostrum; and long, narrow, elastic baleen plates (up to nine times longer than wide) with fine baleen fringes.
Species of the infraorder Cetacea A phylogenetic tree showing the relationships among cetacean families. [1]The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. [2]
Cetaceans are long-lived animals (particularly whales), with a theoretically low mortality rate once they reach adulthood and virtually no predation, even if they remain exposed to diseases and parasites (which are thought to be involved in 25% of cetacean deaths in the Mediterranean, particularly when their proliferation becomes pathological ...
The bottlenose dolphin is a toothed whale in the genus Tursiops.They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus contains three species: the common bottlenose dolphin (Tursiops truncatus), the Indo-Pacific bottlenose dolphin (Tursiops aduncus), and Tamanend's bottlenose dolphin (Tursiops erebennus).
Whales do not form a clade or order; the infraorder Cetacea includes dolphins and porpoises, which are not considered whales in the informal sense. [citation needed] The phylogenetic tree shows the relationships of whales and other mammals, with whale groups [citation needed] marked in green.
The cetacean ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance equalizer between the outside air's low impedance and the cochlear fluid's high impedance. In whales, and other marine mammals, no great difference exists between the outer and inner environments.
Pilot whales can be found in oceans nearly worldwide, but data about current population sizes is deficient. The long-finned pilot whale prefers slightly cooler waters than the short-finned and is divided into two populations. The smaller group is found in a circumpolar band in the Southern Ocean from about 20 to 65°S.