Aquatic mammal

Aquatic and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the platypus and the European otter.

Adaptations

Mammals evolved on land, so all aquatic and semiaquatic mammals have brought many terrestrial adaptations into the waters. They do not breathe underwater as fish do, so their respiratory systems had to protect the body from the surrounding water; valvular nostrils and an intranarial larynx exclude water while breathing and swallowing. To deal with water salinity, cetaceans and pinnipeds have evolved reniculate kidneys also found in bears. To navigate and detect prey in murky and turbid waters, aquatic mammals have developed a variety of sensory organs: for example, pinnipeds have elongated and highly sensitive whiskers that can pick up vibrations from fishes and reveal information about water currents, and toothed whales have evolved echolocation.