page_title: List of semiaquatic tetrapods
section_title: Mammals
hierarchical_section_title: List of semiaquatic tetrapods / Mammals
caption_attribution_description: English: North American Beaver (Castor canadensis), Pohick Creek, Springfield, VA.
context_page_description: This is a list of tetrapods that are semiaquatic; that is, while being at least partly terrestrial, they spend part of their life cycle or a significant fraction of their time in water as part of their normal behavior, and/or obtain a significant fraction of their food from an aquatic habitat. The very earliest tetrapods, such as Ichthyostega, were semiaquatic, having evolved from amphibious lobe-finned fish.
  Some marine mammals, such as the marine otter, the polar bear and pinnipeds, are semiaquatic, while others, such as the sea otter, cetaceans and sirenians, are fully aquatic. The only fully aquatic nonmarine mammals are several manatees and certain small cetaceans. No bird species is fully aquatic, as all must lay and incubate their amniotic eggs, as well as begin raising their young, on land or ice. Similarly among marine reptiles, sea turtles are almost fully aquatic, but must come ashore to lay eggs. Marine iguanas and partly marine crocodiles are all semiaquatic. Most sea snakes are ovoviviparous and fully aquatic. A few freshwater snakes are also ovoviviparous and fully aquatic, but the majority are semiaquatic.
context_section_description: All extant fully aquatic mammals except the sea otter are found in two clades of exclusively aquatic species, Cetacea and Sirenia; the extinct desmostylians are also thought to have been fully aquatic (these groups are thought to have become fully aquatic about 45, 40 and 30 Ma ago, respectively). In contrast, semiaquatic mammals are widely distributed throughout the class. However, extant semiaquatic swimming marine mammals are restricted to Carnivora (among which, pinnipeds apparently appeared about 20 Ma ago). Semiaquatic (carnivorous) rodents have been noted as having larger than normal brains for their size, possibly as a consequence of using their vibrissae for acoustic detection of prey.
  Monotremes
  Platypus
  Marsupials
  Lutrine opossum
  Water opossum or yapok
  Tenrecs
  Otter shrews
  Web-footed tenrec
  †Ancestral sirenians - fossils are known of transitional semiaquatic sirenians, such as the 50 Ma old Pezosiren, which was a hippo-like quadruped
  Proboscideans
  †Moeritherium
  Asian elephant - primarily terrestrial 
  Sloths
  †Thalassocnus - this marine genus of Pacific coastal South America arose about 7 Ma ago, and its most recent species may have been fully aquatic
  Primates
  Allen's swamp monkey
  Crab-eating macaque - feeds opportunistically, but some populations dive for crabs in mangrove swamps
  Proboscis monkey - inhabits mangrove, riparian and swamp forest and has webbed digits
  Humans - some cultures have practiced marine freediving for subsistence for over a thousand years; in the case of the Sama-Bajau of Maritime Southeast Asia, evidence suggests that genetic adaptations facilitate this lifestyle
  Rodents
  Castorimorpha - beavers, pocket gophers, and kangaroo rats
  Beavers
  Caviomorpha - New World hystricognaths
  Capybaras
  Coypu
  Paca
  Myomorpha - mouse-like rodents
  'Crab-eating rats'
  European water vole
  'Fish-eating rats'
  Link rat or Congo forest mouse (Deomys ferrugineus), an African murid
  'Marsh rats'
  Muskrat
  'Swamp rats'
  'Water mice'
  'Water rats' or 'wading rats'
  Lagomorphs
  Marsh rabbit
  Swamp rabbit
  Eulipotyphlans
  Desmans
  Star-nosed mole
  'Water shrews'
  Bats
  Noctilionidae - bulldog bats, a family with only two species, both semiaquatic, one eating aquatic insects, one mainly fish
  Vespertilionidae - vesper bats
  Mouse-eared bats - several species of this mostly insectivorous genus are piscivorous to varying degrees, such as Myotis vivesi (an exclusively marine species), M. pilosus, M. macropus, M. macrotarsus, M. stalkeri, and M. daubentonii
  Carnivorans - while semiaquatic mustelids are widespread, semiaquatic felids are known primarily from South and Southeast Asia, while semiaquatic canids are best known from the Neotropics
  Canidae - foxes, jackals and wolves
  Arctic fox - coastal populations exploit marine food sources, such as fish, invertebrates and seaweed, and may hunt ringed seal pups or scavenge polar bear kills on pack ice
  British Columbia wolf
  Bush dog
  Dhole - often drive their prey into water bodies
  Short-eared dog
  Mustelidae - weasels and otters
  Minks
  Otters (except the sea otter)
  Pinnipedia - seals, sea lions and the walrus
  Procyonidae - raccoons
  Crab-eating raccoon
  Ursidae - bears
  Kodiak bear and other salmonid-specializing brown bear populations
  Polar bear
  Felidae - cats
  Fishing cat
  Flat-headed cat
  Jaguar - facultatively semiaquatic, i.e., have an affinity for water and exploit aquatic prey in a rainforest or floodplain environment, but may also inhabit more arid habitat
  Tiger
  Herpestidae - mongooses
  Crab-eating mongoose
  Viverridae - civets and genets
  Aquatic genet
  Otter civet
  Perissodactyls
  Rhinocerotidae - rhinos
  Indian rhinoceros - primarily terrestrial
  Javan rhinoceros - primarily terrestrial
  Sumatran rhinoceros - primarily terrestrial
  Tapiridae - tapirs
  Artiodactyls
  Bovidae - ruminants
  Anoa
  Sitatunga
  Waterbuck
  Wild water buffalo
  Cervidae - deer
  Chinese water deer
  Marsh deer
  Moose - obtain a substantial fraction of their food  from  aquatic sources
  Pere David's deer - adept swimmers and stand for long periods in water up to their shoulders
  Hippopotamidae - hippos are the closest extant relatives of the fully 
caption: North American beaver, Virginia
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