Most capture sites have long-unburnt vegetation (30-50 years) containing layers of extremely dense vegetation at 0.5-2.5 metres high. Dominant upper-storey species include Eucalyptus, Isopogon, Acacia, Casuarina and Melaleuca. Quandong, Santalum acuminatum (within the northern part of the range) and various sedge species are also important habitat requirements. Extremely variable vegetation types range from sparse low shrublands through to mid-dense woodlands and granite associated vegetation on sandy clay loam or sandy loam, frequently with a matrix of gravel.
The Western Mouse is nocturnal, sheltering during the day in a burrow (20-30 centimetres deep) which consists of a single vertical entrance shaft, connected to a horizontal loop 2-3 metres in diameter with a nesting chamber located opposite the entrance. Other similar sized loops sometimes extend off the main loop, although these have neither entrance holes nor nesting chambers. The entrance shaft is well concealed apparently having been dug from the inside and is commonly located in dense leaf litter. An original shaft (dug from the outside and entering a different part of the loop) is filled in once the burrow is completed. Nesting material consists largely of loose, fibrous plant material.
The Western Mouse is communal, ten animals having been collected from one burrow system in the wild. Individuals have been recorded to travel 600 metres overnight from a trap-site to a burrow.
The diet consists largely of fibrous plant material, flowers of Acacia, Conospermum, Pultenea and Hibbertia and seeds of Hakea, Dryandra and Quandong, and various invertebrates including beetle and moth larvae. In the northern part of its range large accumulations of Quandong nuts can be found under dense low bushes and vegetation (usually within 30-50 metres of mature Quandong trees). These are chewed to extract the kernels which are rich in proteins and oils. At a number of different sites, accumulations of over 100 chewed nuts have been found, piled up to 5cm deep, covering up to 1 square metre and exhibiting various stages of decomposition, suggesting prolonged use as a feeding site. The chewed nuts are distinguished by the small hole and distinct marks left by the incisors.
Pregnant females are found in early to mid-spring and young are born from mid- to late spring, with juveniles (10-15 g) entering the population in early summer. A body weight of 32-37 grams is attained by May or June and animals breed in their first year.
Trapping data suggest that the population density varies between seasons and from year to year but is generally one to seven individuals per hectare. Populations seem to be restricted to distinct areas and vegetation types within conservation reserves.
Reference: Whisson, L(2008). Western Mouse Pseudomys occidentalis In Van Dyck, S. and Strahan, R. (eds) The Mammals of Australia 3rd edition pp. 645-646. Sydney: Reed New Holland
Photo credit to - Photo: Jiri Lochman / Lochman LT
Thanks to C. Hadlow for supplying this article.