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A humpback whale (Megaptera novaeangliae) A leopard seal (Hydrurga leptonyx). Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans (whales, dolphins and porpoises), pinnipeds (seals, sea lions and walruses), sirenians (manatees and dugongs), sea otters and polar bears.
Despite their underwater habitat, whales are mammals. Mammals are not solely terrestrial; some, including whales and dolphins, are fully aquatic the University of Michigan Museum of Zoology reports.
The adaptation of animal echolocation in toothed whales distinguishes them from fully aquatic archaeocetes and early baleen whales. The presence of baleen in baleen whales occurred gradually, with earlier varieties having very little baleen, and their size is linked to baleen dependence (and subsequent increase in filter feeding).
The stocks of species such as humpback and blue whales have recovered, though they are still threatened. The United States Congress passed the Marine Mammal Protection Act of 1972 sustain the marine mammal population. It prohibits the taking of marine mammals except for several hundred per year taken in Alaska.
The whale 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, there is no great difference between the outer and inner environments.
The humpback whale is a fully aquatic marine mammal. Marine mammal adaptation to an aquatic lifestyle vary considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate ocean dwellers.
It was the ancestor of modern whales, dolphins, and porpoises. The cetacea are extensively adapted to marine life and cannot survive on land at all. Their adaptation can be seen in many unique physiognomic characteristics such as the dorsal blowhole, baleen teeth, and the cranial 'melon' organ used for aquatic echolocation.
Many aquatic mammals or marine mammals independently came to have adaptations to live in water, such as similar-looking tail flukes in dugongs and whales. Unrelated herbivores and carnivores have adapted to marine and freshwater environments. [5]