The western mouse or walyadji refers to ''Pseudomys occidentalis'', a species of

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

in the family Muridae. Once widespread across a larger range, it has become restricted to around ten reserves of remnant bushland in Southwest Australia and declared near threatened by extinction. They are small and robust mice that live in burrows in sandy soil, venturing out at night to forage in nearby area.

Taxonomy

murine The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. Members of this subfamily are called murines. In terms of species richness, this subfamily is larger than all mammal families ex ...

species that was first described by George H. H. Tate in 1951, using specimens obtained in 1930. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

is a skin and skull of a young adult collected at Tambellup by J. Baldwin, with Tate referring to a second specimen with a damaged skull as slightly larger. Assigned to a diverse and poorly resolved genus, ''

Pseudomys ''Pseudomys'' is a genus of rodent that contains a wide variety of mice native to Australia and New Guinea. They are among the few terrestrial placental mammals that colonised Australia without human intervention. Natural history This genus con ...

'', the describing author allied the species to a subgeneric classification as '' Gyomys''. The term walyadji is used to refer to the species, but this word does not appear in a literature review of

Noongar language Noongar (; also Nyungar ) is an Australian Aboriginal language or dialect continuum, spoken by some members of the Noongar community and others. It is taught actively in Australia, including at schools, universities and through public broadcasti ...

names for mammals of the region.

Description

This mouse is roughly 10 centimeters long, not counting its tail, which may be up to 14 centimeters in length. It weighs an average of 34 grams. It has a soft, fine, dark gray and yellowish buff

pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket ...

that is interspersed with black

guard hair Guard hair or overhair is the outer layer of hair of most mammals, which overlay the fur. Guard hairs are long and coarse and protect the rest of the pelage (fur) from abrasion and frequently from moisture. They are visible on the surface of the fu ...

s. The feet are white. The species is distinguished by the aquiline profile of nose, and its long tail. The range of measurements for the head and body combined is 88 to 110 millimetres, exceeded by the tail's length of 120 to 140 mm. The hind feet of ''Pseudomys occidentalis'' are 24 to 28 mm, relatively long for the genus, with interdigital pads that are larger than the terminal pads. The proportion of the pads and lack of granulation over the surface of the hind foot distinguishes the species from the ash-grey species '' Pseudomys albocinereus''. They have two pairs of inguinal teats. The weight range of the species is 30 to 55 grams.

Behaviour

The subterranean nests have a single entrance, a shaft that connects to a network 200 to 300 millimetres below the ground. The main tunnel has a nest site at the opposite end of a loop, two to three metres from the entrance, with a network of other loops extending as annexes to the central tunnel. The site may be occupied by up to ten individuals.

Distribution and habitat

The distribution range once extended across Southwest Australia and into the arid interior, this became restricted to a few areas near the Ravensthorpe Range, at

Fitzgerald River National Park Fitzgerald River National Park is a national park in the Shires of Ravensthorpe and the Jerramungup in Western Australia, southeast of Perth. The park is recognised on Australia's National Heritage List for its outstanding diversity of nativ ...

, and several isolated populations in the southern wheatbelt. This mouse lives in loamy soils in areas that have not been burnt recently, and not known at any location that has been subjected to fire in the preceding 30 to 50 years. The terrain has climax vegetation, especially the desert quandong ''

Santalum acuminatum ''Santalum acuminatum'', the desert quandong, is a hemiparasitic plant in the sandalwood family, Santalaceae, (Native to Australia) which is widely dispersed throughout the central deserts and southern areas of Australia. The species, especia ...

'' and

sedge The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus '' Carex'' ...

-like plants. The substrate of the ecological communities in which they are known to remain is sandy or sandy-clay soil that is often intermixed with gravel. Plant genera associated with their remnant sites are ''

Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as e ...

'', '' Acacia'', ''

Isopogon ''Isopogon'', commonly known as conesticks, conebushes or coneflowers, is a genus of about forty species of flowering plants in the family Proteaceae, and are endemic to Australia. They are shrubs with rigid leaves, bisexual flowers in a dens ...

'', ''

Allocasuarina ''Allocasuarina'' is a genus of trees in the flowering plant family Casuarinaceae. They are endemic to Australia, occurring primarily in the south. Like the closely related genus '' Casuarina'', they are commonly called sheoaks or she-oaks. ...

'' and '' Melaleuca'', and the vegetation of their habitat is highly variable, including open woodlands, low and tall shrubland, mallee and heath in open to dense arrangements of plants. After being identified in 1951, the species was known by five specimens until the region's survey and collection of mammals was begun by the state's museum in 1971.

Conservation

The conservations status of the species was assessed as near threatened in 2016, with a declining population in an area of occupancy less than 200 km². The fragmented populations inhabit remnants of its preferred habitat, estimated from earlier surveys to be greater than 10 and a decline less than 30% in three generations. Loss of habitat and a anthropogenic climate change is expected to impact upon the species population trajectory.

References

*Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. pp. 894–1531 ''in'' Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore. {{Taxonbar, from=Q1766353 Pseudomys Endangered fauna of Australia Mammals of Western Australia Rodents of Australia Mammals described in 1951