Name(s): Australian water rat, or rakali, (Hydromys chrysogaster)
Group: Rodents
Size: Length 270-400 mm, plus a tail of 240-345mm; weight usually 700-1000g, with some animals up to 1200g.
Diet: This rodent is carnivorous! Aquatic invertebrates, snails, yabbies, mussels, frogs, fish and waterbirds are all part of its diet. If it lives in water and is tasty, it is likely to find its way into the rakali’s belly. They have even been known to eat turtles and some small mammals.
Habitat: Inland waters including small creeks, rivers and lakes, as well as coastal estuaries, beaches and islands in all Australian states and territories. It also occurs in New Guinea.
Conservation status: Not endangered
Superpower: Adult water rats hold culinary masterclasses to teach their young how to open freshwater mussels – one of their favourite foods. However, the lessons vary from place to place. In some populations, young water rats are taught to put the mussel on a platform by the water’s edge and let the sun dry the mussel so that the shells fall open. In others, rats are taught to bite through the mussel shell and into the adductor muscle that works to keep the shells tightly shut.
Don’t like rats? The rakali is sure to change your mind about Australia’s amazing native rats and mice. This large and beautiful aquatic rodent is about as similar to the mice in your kitchen cupboard as a majestic tiger is to a skulking alley cat.
The name ‘rakali’ is an Indigenous name from the people of the Lower Murray River region, but there are dozens of names for this animal recorded across different parts of Australia. Rakali are common throughout their range, which extends from Tasmania and southwest WA right up to the tropics of northern Australia and New Guinea. They even occur in temporary outback wetlands along Cooper Creek and the Diamantina River. Rakali live in burrows beside the water, and spend time foraging in the water and along the water’s edge. Like many true-blue Aussies, they love the beach and taking a dip in the creek, and are good swimmers and divers.
Unfortunately, many Australians are not aware of the rakali or of how truly magnificent this animal is. It is one of only two freshwater aquatic Australian mammals (the other is the platypus), and it lives all around us – often the only native rodent to be found in our towns and cities. They’re true “Aussie battlers” and very adaptable – I’ve seen them hunting in the Townsville marina among luxury yachts, but also in the pristine rainforest streams of the wet tropics, and in freezing cold creeks high on the New England Tableland. Get to know the beautiful rakali, and you’ll never think of rats quite the same way again.
The rakali’s Latin name – Hydromys chrysogaster – translates as “golden-bellied water mouse”. Along with that beautiful body colouration and signature white-tipped tail, the rakali has webbed feet for swimming, a face full of gorgeous long whiskers for detecting aquatic food, and eyes and ears set high on the head so it can cruise semi-submerged through the water.
Unusually for rodents, the rakali is carnivorous. They hunt both small prey, such as aquatic insects and spiders, and larger animals like yabbies, shrimps, mussels and fish. Fish are taken from below, with the swim bladder punctured as the animal is seized. Rakali also eat waterbirds; Penny Woollard recounts an observation made by a colleague of one intrepid animal “capturing a full-sized musk duck by surprise, grabbing the tail of the bird and hanging on until the frantic duck exhausted itself, then apparently severing its neck”. Woollard and colleagues also recorded water rats eating grebes, swamp hens and a range of other birds. These ain’t no ordinary rats!
A charming rat that swims and dives, eats fish and fowl, and teaches its babies culinary tips and tricks has to be a strong contender in the Australian Mammal of the Year! Vote 1 rakali!
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Originally published by Cosmos as Rakali: no ordinary rat
Karl Vernes
Professor Karl Vernes is a wildlife ecologist at the University of New England. Karl has worked on a wide variety of mammals in Australia and abroad. He has a particular interest in the spatial ecology, diet, and life history of Australia’s wonderful mammal fauna, and he is passionate about mammal conservation.
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