Spotlight on the Water mouse (Xeromys myoides)

Other Names: False water rat, yirrkoo

Conservation status: Vulnerable (Commonwealth Environment Protection and Biodiversity Conservation Act 1999; Nature Conservation Act 1992)

The water mouse is a native rodent that inhabits coastal freshwater and intertidal environments, including saltmarsh, mangroves, and wetlands.

Water mouse, False water rat, yirrkoo.

In Queensland, discontinuous populations have been recorded along the coast from Proserpine in the Whitsunday Region to the Queensland-New South Wales border, including K’gari (Fraser Island), Bribie Island, and Minjerribah (Stradbroke Island). Higher-density populations occur within Pumicestone Passage and southern Moreton Bay, where a large proportion of their range falls within the Moreton Bay Ramsar wetland.

Fun fact: Unlike water rats, the water mouse does not have webbed feet. It is for this reason they came to be known as the ‘false water rat.’

They are one of Australia’s rarest rodents and very little was known about the species before the late 1990s when the first field surveys were conducted.

The water mouse has small eyes and short round ears and is covered in silky, water-repellent, slate-grey fur with a pure white underbelly. They can grow up to 126mm in body length and weigh up to 64g.

The species is mostly active at night and is known to hunt a variety of prey, including crabs, lobsters, marine worms, snails, and molluscs. During the day they shelter in distinctive nests resembling termite mounds, constructed of leaves, peat, and mud. These mounds can be up to half a metre tall and provide protection from tides and predators as well as a safe place to rear young.

If you’re walking through the Moreton Bay Ramsar Wetland and you catch a whiff of pilchards and mouldy leather, there could be a water mouse nearby!

Threats to the water mouse

The main threats to the water mouse are habitat loss, fragmentation, and degradation. Urban development, resource extraction, and wastewater discharge impacting water levels and quality can have direct and indirect effects on water mouse populations. Other pressures include introduced predators such as foxes and feral dogs and cats, habitat damage caused by recreational vehicles and climate change impacts such as sea level rise.

Conservation efforts

The Australian Government’s National recovery plan highlights key conservation actions to improve the conservation status of the water mouse, including conducting surveys, mapping, and research to improve our understanding of their biology, distribution, and habitat, monitoring population trends, and identifying and managing threats and pressures, rehabilitating habitat and increasing community awareness and involvement.

Healthy Land & Water is helping local water mouse populations as part of the Moreton Bay Ramsar Wetland project, by working with Quandamooka Yoolooburrabee Aboriginal Corporation (QYAC) to reduce fox and feral cat populations on Minjerribah. This project aims to reduce predation of Xeromys myoides and hopefully help the water mouse populations recover.

You can help protect the water mouse by keeping cats indoors, keeping dogs on leashes when walking through wetland environments, and reporting fox sightings to local government or local land managers.

The Moreton Bay Ramsar Wetland project is delivered by Healthy Land & Water with support from the Australian Government’s National Landcare Program.