These threatened rodents reintroduced themselves to Arid Recovery
Photo by Helen Crisp
Range and abundance
The Plains Mouse (Pseudomys australis) was once widespread throughout the arid and semi-arid regions of Australia. Since European settlement its range has declined by 50-90% and it is now restricted to the gibber (stone-covered) plains of the Lake Eyre Basin in northern South Australia and the Southern Northern Territory. It is now presumed extinct in Queensland and was last recorded in Western Australia in 1969.
The Plains Mouse weighs between 30 and 50 grams and is one of the largest rodent species still inhabiting the arid zone. It has grey to grey-brown fur above and white or cream fur below with relatively large ears. The tail is shorter or equal to the head-body length. The tail is also bi-coloured, being grey or brown above and white underneath.
The Plains Mouse builds shallow, complex burrows which are dug into cracks in the gibber plain or at the base of shrubs. In burrows dug beneath shrubs, the soil is softer and complex warrens can be built up to 2 square metres in area. Nest chambers are built with dried grass.
During the breeding season, burrows often contain one male and several females, while outside of breeding season burrows can be occupied by up to 20 individuals. The mice leave little runways covered in tracks that connect their burrows and lead off to their feeding areas.
Classic gilgai habitat, favoured by Plains Mice. Photo by Kath Tuft
The Plains Mouse is nocturnal. It usually lives in small colonies, but these colonies can increase in size dramatically after rain. During good years where there is lots of food, Plains Mice will expand into areas not usually occupied, such as sandy plains.
The Plains Mouse mainly eats grass seeds, but will also eat other plant material, insects and small reptiles. The Plains Mouse is able to survive without drinking, obtaining all its water requirements from its food.
The Plains Mouse follows a boom and bust cycle, with breeding occurring primarily after rainfall when there is an increase in food availability. As conditions deteriorate, populations can decline rapidly as food resources diminish. Litter sizes are usually three to four. Weaning takes place 28 days after birth.
The Plains Mouse has had a significant decline since European settlement. The major threat to the Plains Mouse is habitat degradation due to trampling and intensive grazing from cattle and sheep. Predation from feral cats and foxes have also contributed to their decline. They frequently turn up in in the stomach contents of cats shot in the region. The Plains Mouse is now listed nationally as Vulnerable.
What is Arid Recovery Doing?
The Plains Mouse was first recorded in the Arid Recovery Reserve in 2006. A reduction in the number of rabbits in the greater area due to the release of the rabbit calicivirus between 1995 and 2009 led to a gradual increase in extent and area of occupancy for the Plains Mouse. Since 2006 the numbers of Plains Mice in the reserve has increased and now it is frequently recorded during trapping and spotlighting surveys.
Map of Plains Mice records at Arid Recovery when they first appeared in 2006 (left) and recently (right)
It was previously thought Plains Mice needed cracking clay depressions in gibber plains to survive. However, since first being recorded in the reserve, in the absence of feral cats, foxes, rabbits and stock, the Plains Mouse has spread from the gibber plains (where it is typically found) into all types of habitat including stony swales and dunes. It is now clear that its apparent reliance on gibber plains is a refugial effect and it can actually occupy a wide variety of habitats.
Written by Rachael Loneragan (March 2017)