Hydromys chrysogaster Click to enlarge image
Common water rat, Hydromys chrysogaster. Culgoa River/Goodooga N S W Image: Robert W G Jenkins
© Australian Museum

Fast Facts

  • Classification
  • Size Range
    Body 231 mm - 370 mm, tail 242 mm - 345 mm, weight 340 g - 1275 g.


The Water-rat is one of Australia's largest rodents and is usually found near permanent bodies of water.


Well adapted to aquatic life with its webbed hind feet and waterproof coat, the Water-rat can be identified by its large size and long tail with a white tip. The main characteristics that help distinguish the Water-rat from other rodents include:

  • Front teeth: One pair of distinctive chisel shaped incisors with hard yellow enamel on front surfaces.
  • Head: Flattened head, long blunt nose, with abundant whiskers, small eyes.
  • Ears: Notably small ears.
  • Colouring: Variable. Near-black, grey to brown, with white to orange belly. Thick soft waterproof fur.
  • Main feature: webbed hind-feet.
  • Tail: Thick, white-tipped.


The Water-rat is one of Australia's largest rodents and is usually found near permanent bodies of fresh or brackish water.The Water-rat is one of Australia's only two amphibious mammals (the platypus is the other). They live in burrows alongside river and lake banks.


The Water-rat is found in Queensland, New South Wales, Victoria, Tasmania, South Australia, Western Australia (south-west and north), Northern Territory.

Feeding and diet

The Water-rat feeds on a wide range of prey including large insects, crustaceans, mussels and fishes, and even frogs, lizards, small mammals and water birds. It forages by swimming underwater. Once it catches its prey, it usually carries it back to a regular feeding site.

Other behaviours and adaptations

Although native rodents are usually nocturnal, the Water-rat is most active around sunset and may even forage during the day.

The burrow is usually hidden among vegetation and built along the banks of rivers and lakes. The round entrance has a diameter of about 15 cm. In dense populations, males are territorial and defend their areas aggressively. In these circumstances, it is common to see Water-rats with damaged tails as a result of these fights.

Conservation status

During the depression in the 1930s, a ban was placed on the import of furred skins (mostly American Muskrat). The Water-rat was seen as a perfect substitute and the price of a Water-rat pelt increased from four shillings in 1931 to 10 shillings in 1941. The species was heavily hunted during this time until protective legislation was introduced. Populations seem to have made a recovery.

The main threats to the Water-rat today are habitat alteration as a result of flood mitigation and swamp drainage, and predation by introduced animals such as cats and foxes.

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