I grew up in wheat and sheep country where there were very few native mammals around. Maybe that’s why as a kid I took great pleasure in regularly standing on a bridge over the local lagoon in anticipation of seeing the resident Water Rat working its way along the water’s edge. I recall being told how hunting had nearly wiped them out because their soft, durable pelts were much sought after during the lean depression years. The story goes that locals would make traps out of old jam tins, and once caught, the Water Rat pelts would be taken to the local tannery where they would fetch a handsome sum.

I puzzled over how this once over-hunted critter survived in water that no one ever dared swim in because it looked and smelt, well…. just a little like a cess pit. I also wondered how the sleek creature I enjoyed watching ended up with the seemingly undignified name of ‘Water Rat’. Despite the fact that there are many fascinating native rodent species in Australia, it must be said that anything with the word ‘rat’ in its title is encumbered with a bit of an image problem. Even the slickest marketing spin-doctor would struggle to win popular appeal for a rat, let alone a partially drowned rat.

My native lagoon critter looked more like the otters I had seen on nature documentaries. Ok, so I will concede that it is in fact Australia’s largest member of the rodent family and it does have large chisel shaped incisors and abundant whiskers, a bit like a very large…rat. But to this young admirer it was a glistening, streamlined native predator gliding along on its bow wave, as flash as a rat with a gold belly!

Perhaps that’s why there has been an official attempt to change its common name to ‘Rakali’, which is an indigenous name. But I think it’s safe to say that this name change hasn’t really stuck and nor has “Golden-bellied Water Mouse’ which is what its scientific name (Hydromys chrysogaster) translates as; so ‘Water Rat’ it is.

Adult Water Rats are the size of a small possum with the body measuring about 30-35 cm in length while the distinctly white–tipped tail is slightly shorter than the body. They have a flattish square head with small ears and eyes. Their colour varies considerably with some having a brown to black back and a golden belly, while in other areas they can appear slate grey with a white belly. They are well adapted to their aquatic lifestyle with dense water repellent fur. They use their large, partially webbed hind feet as paddles, while their thick tail operates like a rudder.

They occur throughout most of Queensland and much of non-arid Australia where permanent water bodies exist. Along with an additional eight closely related species (tribe Hydromyini) they also occur in New Guinea where they are thought to have originated. Apart from their obvious requirement for water they are habitat generalists capable of occupying an assortment of aquatic environments both natural and man-made, fresh, brackish and saline. They tend to avoid high energy streams, preferring slow moving or still water. As demonstrated by my lagoon creature they also appear to be able to survive in polluted waterways.

Water Rats are opportunistic predators and while they catch most of their prey in shallow waters close to the shoreline, they are also adept at hunting and scavenging on land. They are predominately carnivorous and their diet varies according to location. Prey can include crayfish, aquatic invertebrates, fish, mussels, birds (including domestic poultry), small mammals, frogs and reptiles (including small turtles). Adjacent to urban waterways they have been recorded preying on introduced Black Rats (Rattus rattus). They will also eat carrion, food scraps, the occasional plant and have been observed sneaking meals from pet bowls and camp sites.

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Water Rats like to collect their food and then dine at a ‘feeding table’, shown here as a collection of discarded yabby claws. Photo by Paul Campbell, Flickr (Paul Campbell / outback traveller).

Water Rats are intelligent animals. They remove mussels from the water and leave them in the sun to open prior to eating. There is also evidence to suggest that they can consume Cane Toads without ill effect. Researchers have found them very wary of traps and if caught they don’t make the same mistake twice. If accidentally caught in nylon cray sh traps they will often chew their way out. However like turtles and Platypus, Water Rats can and do drown if caught in an ‘opera house’ style cray fish trap.

Water Rats are generally shy and not often observed; however, one sign that indicates their presence is their habit of dining at a ‘table’. Once captured, prey is carried to a favoured feeding location such as an exposed tree root, rock or log. Discarded crayfish and mussel shells on such a ‘table’, or eaten out fish scattered around a pond, can be a good indication that a Water Rat lives nearby.

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Wonderful photos of the elusive native Water Rat (facing page and above) taken by Leo Berzins (Oystercatcher / Leo, Flickr CC BY-NC-SA 2.0).

Dusk is probably the best time to catch a glimpse of them as they are usually most active after sunset, but they are unique amongst rodents for their occasional day time foraging. By day, Water Rats occupy burrows located on the banks of streams, or shelter in large hollow logs lying near the water. Burrows have a round entrance of about 15 cm diameter. They will use multiple burrows in their territory, including unoccupied Platypus burrows.

Other signs that may indicate the presence of Water Rats include well-worn runways along the water’s edge or regular crossing points. Their scats are torpedo-shaped and about 1 cm long, 8 mm wide. Males leave a distinctively pungent shy scent to mark their territory. Not only are they smelly, the males are quite aggressive and will defend their territory vigorously which can lead to fierce fights with intruders, occasionally resulting in tails being lost or injured.

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This Parks Victoria sign is helping to promote an indigenous name, Rakali, for Australia’s native Water Rat.
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The golden belly and white-tail tip – two distinctive traits of the native Water Rat. Photo by Lizardstomp, Flickr (CC BY-NC-SA 2.0).

Nesting occurs in a chamber at the end of the burrow and in times of plenty they can have multiple litters per year. Litters usually consist of two to four young which usually appear in the warmer months of the year. After about a month of suckling the young are weaned and have to fend for themselves. It is believed that Water Rats normally survive for a maximum of about 3-4 years in the wild and for the most part lead a solitary existence.
They are a seemingly tough and resilient species that appears to tolerate human encroachment and modification of habitat. Today there are urban populations in highly developed rat-races such as inner Sydney and Melbourne. However their relatively short lifespan leaves them vulnerable to population crashes if successive years of drought restrict successful breeding opportunities, especially in marginal habitat. Habitat alteration such as swamp drainage and flood mitigation do pose some risk for this species as does predation by introduced animals such as cats and foxes. They are also predated on by snakes and sh when they are young, and birds of prey will take adult Water Rats.

Despite the hunting frenzy in the 1930s the Water Rat’s distribution doesn’t appear to have altered much since European settlement. As urban and rural land management practices continue to improve, hopefully so too does the habitat of this poorly known Australian aquatic predator. I recently revisited my childhood lagoon and I was pleasantly surprised to see that the banks had been revegetated and the water was much cleaner. Although I didn’t see one, I was also reliably informed that it is still home to a ‘Rakali’. Who knows maybe the name change will catch on after all?

References and Further Reading

Flannery T (1995) Mammals of New Guinea. Cornell University Press.

Harris WF (1978) An ecological study of the Australian Water-rat (Hydromys chrysogaster: Geo roy) in southeast Queensland. MSc Thesis, UQ.

Lee AK (1995) The Action Plan for Australian Rodents. Dept of Environment, Australian Government.

McNally J (1960) The biology of the water rat Hydromys chrysogaster Geo roy (Muridae: Hydromyinae) in Victoria. Australian Journal of Zoology 8: 170-180.

Olsen PD (1995) Water-rat Hydromys chrysogaster. pp 628-629 in The Mammals of Australia (R. Strahan, ed.).

Van Dyck S & Janetzki H (2007) in Wildlife of Greater Brisbane, Qld Museum.

Watts CHS & Aslin HJ (1981) The Rodents of Australia. Angus & Robertson.

Woollard P, Vestjens WJM and Maclean L (1978) The ecology of the eastern water rat Hydromys chrysogaster at Gri th, NSW: food and feeding habits. Australian Wildlife Research 5: 59-73.

Article by Nick Clancy Land for Wildlife Officer Sunshine Coast Council

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29 responses on “The Australian Water Rat: A little known aquatic predator

  1. Saw what I believe to be a rakali in a big pond at Maggie Beer’s farm in Nuriootpa, South Australia. Was bowled over. Made my holiday! (9..3..18)

    1. I’m happy to say we have a family living under my jetty
      In. North Yunderup
      Western Australia

      I’ve seen a really big one
      And it’s always been to quick for me to get a photo

  2. Hello Nick. I like your article on my favourite wild animal.
    I am pleased to say that today in our property’s Winter Creek on the Southern edge of thr City of Ballarat, Victoria , I saw a young teen rakali . It was about half as long as the last adult I saw in the creek.
    This is my first sighting for 4 or 5 years when I accidentally burnt a blackberry bush which killed an adult rakali. A few weeks later then I found another dead on a ford of the same creek.
    I have waited hoping they would re colonise the creek. I had just decided to take action to reintroduce them starting with water testing then asking the local Ballarat office of the Victorian Wildlife Department how I could reintroduce them when I saw this teen water rat today.
    It was near a short finned eel which rushed to the area in the creek that the rakali rushed from. Would the eel kill the rakali?
    Thanks for your great article.
    I would be pleased to continue advising my contacts with rakali if you agreed.

  3. Saw two Rakali just after dusk last night on the Queens Wharf Road below Miller Park, Brisbane. Presumed to be a mother with one young feeding on a vine running along a fence. Not sure if they were eating berries or insects. The juvenile was feeding while hanging from its tail. Have pics if you’re interested – they were not shy and were happy to hang around for the photo shoot – I trailed their activity for about 5 to 7 minutes. Lyn

  4. I have seen Rakali powering along, swimming on the sea-surface at sunset in my local marina in Port Phillip bay, and their ‘dining’ evidence (crab & shellfish) on the back ends of low-freeboard boats.

  5. We have a resident rakali in the Boosey Creek Nth East Victoria, he is often seen in the daylight browsing the banks for food.

  6. I was surprised when I read you saying “water rat it is”. I was sure you would put the emphasis the other way around. I note that some of those who comment prefer rakali. I am in the latter camp, as the name does matter. It’s not a rat, it’s a rakali. Land for Wildlife should educate on the difference.

  7. I saw one a year ago, foraging through debris washed up on the bank of a flooding creek next to the forest here in Eudlo. When it noticed me it slipped into the rushing water and swam away strongly upstream, looking like an Otter.

  8. I have a lovely Rakali living just out back in my local park. He gets about in Aitken Creek Craigieburn. Such a beautiful animal to watch in motion. The swimming style is awesome to see. Rakali wiggles in a beautiful way. The other day Rakali came out of the water for a look around and sat on my boot whilst I stood there in amazement. So happy to have such a beautiful creature living just out the back.

  9. Just walking along edge of Merimbula Lake next to shopping centre with a Rakali swimming at walking pace along side.
    A beautiful sight

  10. I first saw what I believed to be a Rakali twenty years ago whilst walking along the Ovens River near Bright in Victoria. It was swimming and diving under the water level for short intervals. At first I thought it was a platypus but when I mentioned it to the owner of the nearby motel he informed me it was most likely a “water rat”. My next encounter with Rakali was at a small island connected by bridge at Victor Harbour in South Australia.. That particular sighting was early morning whilst still dark. I had walked across the long bridge and along the edge of the water when I saw what I thought was a small Wallaby hopping around on the rocks. It appeared reddish brown in colour. All of a sudden it was in the water and disappeared. I have now become fascinated with our Rakali and whenever I visit the Healesville Sanctuary I always visit the Rakali display.

  11. Have seen rakali/water rat in the Port River, Port Adelaide over the past two evenings at twilight. The first night we couldn’t figure out what it was …not a shag, not a dolphin, so we sought the advice of a local (as we have just bought property on the Port River), and he said it was a water rat. Eeeek! On researching this aquatic animal , I am so happy to find it is a native as I have had experiences with rats both in inner Sydney, a temple in India and in Wewak, PNG, so they are not my most favourite creatures, Tonight when I was walking over the Hart Street bridge, i noticed the same furry head and swimming trail so I stopped and observed. Rakali climbed on a rock, shook his whiskers and preened himself, hopped back into he water, then onto another rock and so on. Methinks water rats right throughout Australia (and are hopefully bushfire survivalists) are alive and well. No fire will threaten them here…

  12. Do rakali climb? We live on a bush block, with a dam, and on clay country while holds water with good rain. I kept finding half eaten cane toad carcasses on the mat outside the door on the upstairs deck. This happened every night for about a week, with them all left on the mat. One night I startled an animal from amongst the self-watering pot plants on the deck, where our green tree frogs live. He moved so fast I couldn’t see him. He was just a dark shape that was there then gone. Does this sound like it could be the behaviour of a water rat? I love that he eats the cane toads (tongue, stomach, hands and feet). Do Black Rats eat cane toads and eat at ‘tables’ or is this behaviour unique to Water Rats?

    1. Thanks for your query. Rakali are an extremely agile species on land and in the water. They readily climb river banks and along logs and over rocks and flood debri but there are limits to their climbing ability. Having webbed hind feet, their physiology is clearly geared towards an aquatic habitat rather than arboreal. In addition to Rakali there is a growing list of native wildlife that have been recorded preying on Cane toads, this includes other small mammals, reptiles such as Water dragons and Crocodiles and a number of bird species. Without knowing where you are it’s a little difficult to guess what your Cane Toad eating predator is.

      Rakali have been recorded utilising waterside human buildings such as wharves so it is possible, but probably unlikely that this is your visitor. If it’s happening at night you can rule out the majority of the birds and reptiles, (Keelbacks swallow young Cane toads whole). Depending on where you are you night time visitor could be a Melomys which is an arboreal native rodent which are known to eat Cane toads. In regard to Rattus rattus they are very agile climbers. They are omnivorous and opportunistic feeders and while they do leave food remains in caches they are not really a feeding ‘table’. We are not aware of any evidence of them eating Cane Toads.

  13. Saw two large individuals in Meadow creek on our property in Gunning NSW. I’d never heard of them before apart from occupying the tank stream in Sydney.

  14. I have just returned from a walk along Gardiners Creek in Blackburn South Vic.7.30 pm. I saw this creature that reminded me of a ring tail possum. Swimming around, above and below the water, foraging around the waters edge. It looked black apart from its white tipped tail. The event lead me to this web site and I was surprised to discover that this was a “native” rat, quite exiting! I’ll have to contact the council tomorrow, to see what they know.

  15. I recently saw a water rat on the edge of Lake Hamilton, Hamilton, Victoria. Had Buckley’s of trying to catch it on camera. My sister and I were walking on the track and saw it swimming. While scrambling for the iPhone, it jumped out, ran across to the track and back into the lake. We had time to see it’s rather large body and white tipped tail. It then decided to get out and make a run for it. I was way too slow with the iPhone. It ran back across our path and disappeared into a polypipe in the wall of the weir. Did all this in the blink of an eye – my camera captured the movement but not Rakali!

  16. If time, please respond to previous email. Happy to learn more about Rakali and if numbers are quite robust in Hamilton area. I’d never seen one before.

  17. During my youth I often observed “Water Rats” as they were then know on the banks of Farmers Creek at Bowenfels ( Lithgow ). This was in the 1950s. On one occasion one was being preyed on by a red bellied black snake. I was on the opposite of the creek and watched the action for about half an hour, but the rat prevailed and lived to live another day.

  18. Saw a Rakali on 6 December 2020 midday in the Loddon River near Kerang
    Despite fishing many rivers in Victoria I did not know they existed. It appeared to be larger than usually described – about 40 cm long. Unfortunately did not get a picture.

  19. Hi Nick,
    We live not too far from Lake Cooroibah on the Sunshine Coast and have a bit of a mystery on our hands. For the last couple of weeks, we have noticed dead toads with some of their insides ripped out and for the last 3 nights, these have been in the chicken run. I googled it and it seems your rats have learnt how to eat the heart and liver of toads so you think the killers could be your water rats? Also, are they noisy as we heard something screeching last night and have no idea of what it could have been? Thanks and regards. Sharon.

    1. Hi Sharon. Quite a few native animals have learnt to eat Cane Toads by turning them over and eating their belly, and thereby avoiding the toad’s poisonous glands on their back. Crows, butcherbirds, kookaburras, Bush Stone-curlew will all have a go at eating a toad. Rats will eat toads too. Its a good chance that you have the introduced Black Rat (Rattus rattus) in your chook pen, rather than the aquatic Water Rat. As to the noisy screeching, we are not sure – it could be feral pigs or a Barn Owl – a simple Google search will give your several Barn Owl calls to listen to.

  20. Seems we have one living under our deck on a canal in Mountain Creek, QLD. I have some great video footage of one scampering along the top of our gate to the beach. Had thought it was a ring tail possum until looked at the photos and description here. I wonder where we’ll find the table and burrows.

  21. I occasionally see Rakali here. I saw another one today, meandering along the edge of the Torrens River at Paradise, SA – Right by my house.

  22. Hello Nick
    I saw my first Rakali at the Ballarat lake wendorie last week while sitting having my lunch and then this morning there was one swimming in my dam right in front of me.
    Our house sits right on the waters edge at Bullarto near Daylsford in vic and we can watch the wildlife without disturbing them. Are they just more prevelant at this time of year or are their numbers increasing?

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