The River Conservation Society is undertaking research into the wild population of the Rakali, or water rat (Hydromys chrysogaster), in the Avon River environs. This animal is well adapted to an aquatic life and is one of Australia’s largest rodents. The water rats ancestors are believed to have arrived in Australia from Papua New Guinea approximately 5 – 10 million years ago.
Rakali have adapted to living with humans, unfortunately to its own detriment, due to being hunted for its fur before becoming a protected species. However, the species has become susceptible to potential threats such as habitat alteration due to flood mitigation and urbanisation and predation by introduced animals.
It is a distinctive rodent well adapted to an aquatic existence. A large animal between 23 – 40 cm in length (not including tail) with large webbed hind feet and a waterproof fur coat. It can be identified relatively easily by its large body length, long and thick tail with a white tip at the end and webbed hind feet.
The water rats diet consists of large insects, fish and crustaceans and can even include frogs, small lizards and small mammals. Once it catches its prey it usually carries it back to a regular feeding site to consume it.
Its habitat is usually near permanent bodies of fresh or brackish water and lives in burrows alongside riverbanks. It has been known to nest in hollow logs along riverbanks or near water bodies and is a strong swimmer.
The water rat is most active around sunset and sunrise but can be seen foraging during the day. Males tend to be solitary animals and are very territorial. They will defend their patch vigorously against other males which intrude into their area.
The purpose of the project being undertaken by the River Conservation Society is to establish if there is a breeding population of Hydromys chrysogaster still active in the region. Are the animals present a unique sub species of Hydromys specially adapted to this inland area and are they under threat, or at worst, have they become extinct from the Avon River system. Should the water rat be deemed under threat in this area then a breeding program will be explored to increase numbers and reintroduce this unique animal back into the Avon River environment. Update December 2021: Commencing in 2022 this project will be funded through a grant from the State Natural Resource Management Program WA