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While the majority of cetaceans live in marine environments, a small number reside solely in brackish water or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons.
'True' river dolphins are descendants of ancient evolutionary lineages that evolved in freshwater environments. [12] Some species of cetacean live in rivers and lakes, but are more closely related to oceanic dolphins or porpoises and entered fresh water more recently. Such species are considered facultative freshwater cetaceans as they can use ...
While the majority of cetaceans live in marine environments, a small number reside solely in brackish water or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons.
While the majority of cetaceans live in marine environments, a small number reside solely in brackish water or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons.
Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Pinnipeds are semiaquatic; they spend the majority of their time in the water but need to return to land for important activities such as mating, breeding and molting. Sea otters tend to live in kelp forests and estuaries. [1]
However, cetaceans are often indirect victims of fishing, in at least two ways. The first is the phenomenon of "bycatch", whereby small cetaceans (particularly dolphins [56]) can become trapped in nets, where they have been attracted by the high concentration of fish and end up drowning. [57]
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.
Groups even attack larger cetaceans such as minke whales, gray whales, and rarely sperm whales or blue whales. [71] [72] Other marine mammal prey species include nearly 20 species of seal, sea lion and fur seal. [73] These cetaceans are targeted by terrestrial and pagophilic predators. The polar bear is well-adapted for hunting Arctic whales ...