What is a water rat? - briefly
The water rat denotes a semiaquatic rodent, such as the Australian species Hydromys chrysogaster, adapted for swimming with webbed hind feet, dense fur, and a water‑repellent coat. It inhabits streams, rivers, and coastal wetlands, feeding on aquatic invertebrates, fish, and amphibians.
What is a water rat? - in detail
The water rat, a semi‑aquatic rodent of the genus Hydromys, belongs to the family Muridae. It is native to the coastal and inland waterways of Australia, New Guinea, and some surrounding islands. Two recognized species—Hydromys chrysogaster (the Australian water rat) and Hydromys hussoni (the New Guinean water rat)—differ primarily in size and fur coloration.
Physical characteristics include a streamlined body, dense waterproof fur, partially webbed hind feet, and a laterally flattened tail that functions as a rudder. Adults weigh 350–800 g and measure 25–35 cm in head‑body length, with the tail adding another 20–30 cm. The eyes and ears are positioned high on the skull to remain above water while the animal swims.
Habitat preferences encompass fast‑flowing streams, rivers, swamps, and mangrove creeks. The species constructs burrows along banks, often with entrances just above the waterline, providing refuge from predators and flood events. Seasonal migrations occur when water levels rise, prompting individuals to move downstream.
Diet consists mainly of aquatic invertebrates, small fish, amphibians, and crustaceans. Opportunistic feeding includes carrion and plant material such as tubers. Foraging behavior is nocturnal; the rat detects prey using vibrissae and acute hearing, then pursues with strong, paddling strokes.
Reproductive cycle features a gestation period of approximately 30 days, after which litters of 2–5 young are born in underground nests. Juveniles are weaned after three weeks and become independent by two months. Breeding can occur year‑round in tropical regions, while temperate populations show peaks during the wet season.
Conservation assessments list the Australian water rat as “Least Concern” due to its broad distribution and adaptability, though local populations may decline from habitat modification, water pollution, and introduced predators such as feral cats and foxes. Protection measures focus on preserving riparian vegetation and maintaining water quality.
Key distinguishing traits from other murids:
- Fully webbed hind feet
- Water‑repellent coat with a oily sheen
- Tail flattened laterally, not cylindrical
- Preference for permanent water bodies rather than terrestrial habitats
Understanding these attributes clarifies the ecological role of this rodent as a predator of aquatic organisms and an indicator of freshwater ecosystem health.