Mouse
House Mouse (Mus domesticus)
History and distribution
Mice are found worldwide and the introduced house mouse probably came to Australia with the First Fleet. Mice are closely associated with human activity and are now distributed throughout the continent, especially in agricultural and urban areas.
Normally population levels are relatively low, however, when conditions are favourable mice numbers can increase exponentially to plague proportions and they become a serious pest. Similar plagues are uncommon in other countries.
The earliest reported mouse plague in Australia was in 1917 on the Darling Downs in Queensland and they have been occurring, with increasing frequency, ever since. Mouse plagues now erupt in the grain growing regions of Australia on average every three years, causing massive disruption to communities and losses to farmers.
Biology
The introduced house mouse is found in a wide variety of habitats in Australia including houses and buildings, agricultural areas, and desert environments. In agricultural regions they often live along fencelines as the accumulation of vegetable matter provides good nest sites, there is usually a good supply of grass seeds, and fencelines are mostly in close proximity to crops. Mice eat a wide variety of food including seeds, grasses, insects, fruit and vegetables. Mice will also gnaw on any hard surface including wood, plaster and plastic, with electrical cables and wiring particularly susceptible.
Mice breed in the southern hemisphere from August to May. They breed from 6-8 weeks of age and a female mouse is pregnant for 19 days then re-mates 1-3 days after giving birth. Litters contain 5-10 young and one breeding pair of mice and their offspring has the potential to produce 500 mice in just 21 weeks.
Damage
Mice cause severe economic, social and environmental damage during plagues – damaging crops, stored products and equipment. The Grains Research and Development Corporation (GRDC) estimates that between 100,000 and 500,000 hectares of grain crops are affected each year. The major plague in South Australia and Victoria in 1993 was estimated to cost at least $55 million in grain losses. A major plague now may cost over $150 million in lost production.
The problems of mouse plagues are not simply economic. Swarms of mice can invade households, hospitals, livestock pens, food storage and other facilities causing significant damage to infrastructure. They also pose a major threat to health and welfare, inflicting stress on humans and livestock. Mice also carry a number of diseases which affect humans and livestock including Salmonella and swine encephalomyocarditis.
Management
Mice have traditionally been controlled using trapping and chemical poisoning. However, all current rodenticides are non-specific toxins and can pose a significant risk to non-target animals and human health. Poisons are also time-consuming and expensive to apply.
Biotechnology is being used to develop a new approach to controlling mice through limiting their reproduction with fertility vaccines. This can potentially be used in conjunction with changes in farming practices to reduce the food and shelter available for mice.
