Water Mouse

Xeromys myoides is a small semi-aquatic rodent characterised by soft grey-brown fur, a pale underside, and a relatively short tail compared to other murids. It constructs distinctive above-ground nesting mounds from mud and vegetation, often built around root systems in mangrove and saltmarsh substrates, with underwater entrances that provide protection from predators and tidal fluctuation. It is largely nocturnal and carnivorous, feeding on crabs, molluscs, and other invertebrates found in intertidal and freshwater wetland sediments.

As a mid-level predator, it contributes to the regulation of invertebrate populations within coastal wetland food webs.

The species occurs in restricted, disjunct populations across northern and eastern Australia and in parts of Papua New Guinea. It is closely tied to wetland and coastal supratidal habitats, including mangrove forests, saltmarshes, and freshwater sedgelands near the coast, where soil moisture and vegetation structure support its mound-building behaviour.

Population decline is driven by ongoing habitat degradation from livestock grazing, aquaculture development, and expansion of non-timber crops into coastal floodplains. Urban and agricultural wastewater discharge and broader pollution have altered water quality in occupied wetlands, while habitat shifting linked to changing hydrology and sea-level dynamics further reduces suitable nesting ground. Invasive species, including predators and habitat-modifying flora and fauna, add additional pressure.

Conservation responses include habitat protection within some coastal reserves, mapping and monitoring of known colonies, and research into mound distribution to guide land-use planning. Regulatory recognition under national and state threatened species legislation in Australia has supported some habitat safeguards.

Given continuing wetland conversion and cumulative pollution pressures, the species' population trend remains decreasing, and its long-term outlook depends on sustained habitat protection across its fragmented range.