Features

The Pilliga Mouse, a type of native rodent belonging
to the genus Pseudomys, is a remarkably well -adapted animal to its environment. Its two greatest threats, fire and predation, have been turned into its greatest assets as it thrives in a precarious world.

Only recently described as a species in 1980, the Pilliga Mouse is closely related to a group of similar- sized mice, the New Holland Mouse and the Delicate Mouse. Recent genetic work has shown that the distinctions between these three is a little blurred. The Pilliga Mouse, however, is recognised as a nationally threatened species because, when it was listed, only about 12 of the animals were known to science. The Pilliga region is also famous for its large fires and potentially this could prove a threat to the little mouse.

PHOTO DAVID PAULL
The Pseudomys pilligaenis– Pilliga Mouse

More study has recently been conducted on this small creature and results have shown it to be a tough survivor. More trapping efforts have been made for two studies based at the University of New England, one in the Pilliga state forests and one in the Pilliga Nature Reserve.

These studies looked at the population, ecology, physiology, diet and habitat selection of this mouse. A large fire swept through the Pilliga in 1997, making it possible to monitor the post-fire consequences for this species. The studies have shown that at times this animal is locally abundant, while at other times only the odd animal is caught, often in the same areas.

The creature's life is shaped by seasonal ebbs and
flows. In the Pilliga state forests, there are a lot of Ironbark/cypress pine habitats that the Pilliga Mouse avoids — instead it seeks the shrubby habitats dominated by Melaleuca and other heathy plants. A strong relationship was found between preferred habitat and a low shrubby understorey in the state forests but in the nature reserve it was found also in more open areas.

Pilliga Mice live communally in simple burrow systems, comprised of two entrances and nest chamber, lined with leaves, some 20–30 cm below the surface. They may stay in these same burrows for up to six months of the year, particularly during the cooler months.

Autumn and Winter were times when most numbers of mice were captured because they were found to congregate in certain areas — possibly for limited food resources or for social reasons. Studies of its diet showed that during winter it eats a lot of fungus, while in summer it turns more to seeds. It also eats insects and green shoots, making it a very flexible feeder.

The reason why the Pilliga Mouse selects shrubby understoreys could be also linked to an anti-predator behaviour or adaptation. In an analysis of fox scats from the area, no evidence of Pilliga Mouse predation was found. This suggests that this animal’s behaviour, including the shelter it keeps, make it too difficult for the fox to catch.

However, its greatest adaptation is the
Pilliga Mouse's ability to use fire to help its survival. As they hide in their burrows any fire would sweep across the surface, leaving the animals safe below ground. For the mouse it was then a question of what to do next, as vast areas of bush were laid bare from the intense fire of 1997.

Trapping showed that, straight after the fire, animals were found in scattered little refuge areas, such as gullies where some grass had remained. They were also found in large numbers in adjacent unburnt areas.

This animal is probably capable of travelling long distances to find refuge habitat and capable of putting up with times of overcrowding. Predation is a real threat during this time of the mouse’s life; the only known predator, the owl, probably take its biggest toll on this animal straight after fires.

After about a year’s growth in the right habitats, the mouse is again able to find suitable cover and forage. Many of the plants, such as the Melaleucas, grow back quickly after fire by sending sprouts up from the underground tubers. So by the second autumn, a number of large congregations were found in these low shrubby plains.

In the state forests study, the largest numbers were
found in such areas, with mothers and males sharing burrows with the young from the previous year. Finding mates for the next season may also occur at this time.

Spring-time seems to be a period of dispersal for the Pilliga Mouse, as capture rates dropped off at this time. Pregnant females are probably finding areas of good seed resources for her growing family and need the space. Some mothers will stay in the preferred over-winter areas, but all males and year-old animals appear to leave.

Whatever it is that makes the young regrowth so attractive to the Pilliga Mouse, an important link obviously exists between its survival and the periodic burning of its habitat. Perhaps equally important is the fact that there is always unburnt habitat that the mouse prefers and into which it can escape. Ensuring this outcome is the key to the survival of this unique rodent.