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Queenscliffe Herald Article - May 2006

The Eastern Water Rat

Michelle Smith
for the Swan Bay Environment Association

The Eastern Water Rat (Hydromys chrysogaster) is commonly and widely distributed throughout Australia, and can often be seen at dawn or dusk on the shores and waters of Swan Bay and the Queenscliff Harbour. Due to their size, body shape and aquatic habits, the Water Rat is commonly associated with the North American otter, and has evolved (along with the Platypus) to fill this niche in the Australian environment.

The Water Rat is one of Australia’s largest native rodents (about the size of a rabbit) and is well adapted to a semi-aquatic mode of life. Their bodies are sleek and covered with water-repellant fur, and their large, partially webbed hind feet provide the Water Rat with effective paddles. The head is long and flattened, with long whiskers and slender ears that are closed when the animal is submerged. One of the most distinguishing features is the thick, white-tipped tail, which functions as a rudder while the animal is swimming.

The thick fur not only keeps the animal warm after swimming, but is also assists with locomotion through the water by providing additional buoyancy. Water rats in the Queenscliff region are a dark brown colour above, with a deep orange or golden belly. Due to this colourful, closely furred pelt, water rats were once hunted for their fur, however legislation enacted in the 1930’s has led to the protection of the species.

Water rats are predominantly carnivorous animals, and take most of their prey from the water. They have incredibly strong teeth which enable them to consume a range of prey including hard mollusc shells, fish, aquatic birds and their eggs, crabs, yabbies, spiders, lizards, frogs, insects and small mammals. Once captured, prey items are carried in the mouth to a flat elevated surface (such as a rock, jetty or boat deck) for consumption. Water rats are clean and fastidious eaters, and they dismember their prey on a “feeding table”, leaving behind piles of crab shells, yabbie remains, fish scales, bones, mollusc shells and feathers.

Observations of the components of feeding tables around Swan Bay indicate that water rats of the area feed mainly on crabs, with Rock, Shore and Surf crabs comprising approximately 90% of the contents of feeding tables investigated. These crab species are generally found on mud flats or sand in shallow waters, and are common in Swan Bay.

The establishment of rock piles, such as in the Queenscliff harbour and on Swan Island, provide water rats with alternative nesting sites, and animals can often be observed foraging or consuming prey in these areas. Water rats dig burrows close to the water line, and these burrows are often hidden amongst the root systems of coastal plants, especially Coast Saltbush, which is one of the dominant species of the Swan Bay foreshore.

Unlike most native rodents (which are nocturnal), water rats are diurnal, meaning that they are often observed during the day as well as at night. Observations by the author indicate that water rats in Swan bay are most active at dusk and dawn. They are strong and silent swimmers, and often a V-shaped ripple can be observed as they glide through the water. So keep an eye out when wandering around Swan Bay, and you might be lucky enough to observe footprints, feeding tables or even one of these attractive native rodents.


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