Hydromys – Water rats

A group of chunky, semi-aquatic rodents that are basically the “otters” of the rat world. They live in Australia, New Guinea, and nearby islands, and their bodies are built for a life spent half in water, half on land. The best-known species is the Australian water rat (also called rakali), but several close relatives swim in creeks, rivers, lakes, and mangroves further north.

At a glance, they do look like big rats, but look closer and you’ll notice clues: a broad head with a blunt snout, dense waterproof fur, small rounded ears, and a thick tail that’s often dark with a pale or white tip. Their back feet are large and partially webbed, acting like paddles, while the front feet are smaller and good for holding food.

Water rats are powerful swimmers and divers. They hug the edges of rivers and shorelines, slipping in and out of the water with practiced ease. Their fur traps a layer of air, keeping them warm in chilly streams, and their long whiskers help them feel their way around in murky water or at night. They usually come out around dusk and during the night, patrolling regular routes along the bank, diving to search under rocks or logs, and climbing back out to eat on a favorite flat stone or root.

Diet-wise, they’re adventurous and fairly fearless. Water rats eat crabs, yabbies, freshwater shrimps, mussels, fish, frogs, insects, snails, and even the occasional bird or small mammal if they can catch it. One of their party tricks is grabbing tough prey like crabs, hauling them to shore, and flipping or tearing them apart with clever paws and strong teeth. In some coastal spots, they’ll swim out around jetties and rock walls, raiding for discarded bait or hunting among seaweed like miniature otters. They’re not strict meat-only eaters, though; they’ll nibble on plant material if the opportunity arises.