The marine mammals are thriving in the lake and surrounding wetlands after their numbers plummeted during the drought.

A community survey of water rat numbers across the state found Lake Wendouree had large numbers of the native rodents, with other healthy populations around Shepparton and in coastal areas.

Around the lake they are most commonly seen in the water and on the shore in the early morning and evening near Pipers cafe and in the Fairyland area, and are often observed gnawing on small fish, yabbies, frogs and other aquatic invertebrates.

“A lot of people don’t even realise Australia has a very wide range of rodent species, but there are more than 50 species of native rodents who have been here for millions of years,” said Australian Platypus Conservancy chief Geoff Williams.

To get over most people’s aversion to rats, researchers prefer to use their indigenous name rakali.

Rakali populations are notoriously difficult to survey because they are very clever animals and often outsmart the traps, or use their very sharp teeth to chew their way out.

When the APC began surveying platypus numbers their methods also trapped rakali, so they now study both species.

“They are a very difficult species to study and as a result we still don’t know much about them,” Mr Williams said.

“This is not a species that copes particularly well with drought, and in many places particularly in central Victoria their numbers really seemed to plummet after the drought and we’re trying to get a handle on where they are doing well.

“They certainly seem to have come back well at Lake Wendouree, but we still know there’s a fairly hefty toll on water rat numbers through their interaction with people.”

The biggest killer of water rats is illegal yabby nets, predators including dogs, cats and foxes, and from people targeting them in the belief they are introduced rats.

Now is the best time to see them around the lake as they are more active during the day in winter.

“Although they are usually active during the night, in winter when it’s colder they are a bit more active in the day. Although they have very nice fur, and used to be hunted for it, it’s not as thick as a platypus so they can’t maintain body heat in the way platypus can so they have to come out of the water to warm up,” Mr Williams said.

Unlike regular rats,  the hind feet of the rakali are partially webbed to help with swimming while their front paws are used like hands. The back half of the tail is white, which easily distinguishing it from other rats.

You can contribute to the survey by reporting any sightings of water rats (even dead ones) to the APC via platypus.asn.au or 5157 5568.