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A common bottlenose dolphin (Tursiops truncatus). A dolphin is an aquatic mammal in the clade Odontoceti (toothed whale).Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the brackish dolphins), and possibly extinct Lipotidae (baiji or Chinese river dolphin).
Swimming mammals, such as whales, dolphins, and seals, use their flippers to move forward through the water column. During swimming sea lions have a thrust phase, which lasts about 60% of the full cycle, and the recovery phase lasts the remaining 40%. A full cycle duration lasts about 0.5 to 1.0 seconds. [3]
However, at higher speeds dolphins and porpoises will seek out the pressure wave and its maximum energy zone in order to ride the wave by holding their flukes in a fixed plane, with only minor adjustments for repositioning. [19] Wave-riding reduces the energetic cost of swimming to the dolphin, even when compared to slower swimming speeds. [19]
The paradox was to figure out how dolphins can obtain such high speeds and accelerations with what appears to be a small muscle mass. Gray made an estimate of the power a dolphin could exert based on its physiology, and concluded the power was insufficient to overcome the drag forces in water.
A great cormorant swimming. Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fish, molluscs, amphibians, reptiles, birds, and mammals.
Although river dolphins do not possess fully developed hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. River dolphins are slow swimmers in comparison to oceanic dolphins, which can travel at speeds up to 35 miles per hour (56 km/h); the tucuxi can only travel at about 14 miles per hour (23 km/h). [26]
Apparently, dolphins rarely enter farms, and when they do, they quickly swim through them. [61] The building of mussel farms seems to have led to a decline in the number and group size of dolphins passing through the bay and they herd prey less when near the farms. [62] [63] Mussel farms are also obstacles for echolocation. [61]
The dolphins drive a school of fish towards the shore where humans await with their nets. In the confusion of casting nets, the dolphins catch a large number of fish as well. Intraspecific cooperative foraging techniques have also been observed, and some propose that these behaviours are transmitted through cultural means.