Document ID: chunk:federal_register_of_legislation:F2023L01713:body:0:p15
Version: federal_register_of_legislation:F2023L01713
Segment Type: other
Provision Reference: 
Character Range: 113405–116235

information presented here focuses on aspects of water mouse ecology that are relevant to recovery objectives and actions and that highlight critical information gaps.

3.1                  Taxonomy
Uncontroversially accepted as Xeromys myoides Thomas (1889) (Rodentia: Muridae) and commonly called the water mouse. It is also recorded in the literature as the false water rat or false water-rat in reference to its closest relative in Australia the native Rakali/water rat (Hydromys chrysogaster). In some locations it is colloquially known as the mangrove mouse.
The water mouse is the only living member of the genus Xeromys. A genetic analysis of 120 species of rodents from the Hydromyini tribe in New Guinea and Australia by Roycroft et al. (2022) suggested the water mouse and the Rakali/water rat both evolved in New Guinea before independently colonising Australia. They are the only two species within the Hydromys division that occur in Australia, yet they are only distantly related to each other within this diverse division of at least 17 species. The closest relatives of the water mouse occur in New Guinea, being several species of moss mouse (Pseudohydromys spp.) and the northern groove-toothed shrew mouse (Microhydromys richardsoni).
Despite its disjunct distribution, a phylogeographic and population genetic analysis strongly supports the current designation of a single species and no subspecies for the water mouse in Australia (Benfer et al. 2014). The genetic relationship between the water mouse in Australia and southern New Guinea is unknown due to a lack of genetic material from New Guinea (Benfer et al. 2014), although it is morphologically indistinct (Hitchcock 1998).

3.2                  Description
The water mouse is a small and distinctive rodent that is about twice the size of a house mouse (Mus musculus) (Thomas 1889). It has a maximum recorded head-body length of 126 mm and a maximum weight of 64 g (Gynther & Janetzki 2013). The pelt, which is water- and mud-resistant, is silky and dark steel-grey in colour with a characteristic abrupt change to a pure white underbelly, lower snout and cheeks (Thomas 1889; Redhead & McKean 1975; Van Dyck 1996; Gynther & Janetzki 2013). There is usually white spotting through the fur of mature adults from Queensland (Van Dyck 1996), and the fur of older individuals can be grizzled grey with a rufous wash to the sides (Gynther & Janetzki 2013).
In the field, the water mouse can be distinguished from other rodents by its colour, silky fur, and tail that is shorter than its head-body length (Gynther & Janetzki 2013). Despite occurring in intertidal and semi-aquatic habitats, the hind feet of the water mouse are not webbed (Thomas 1889). The water mouse has a strong, acrid odour (Gynther & Janetzki 2013).
Figure 1: A compilation of water