Mice: a case study
When Europeans arrived in Australia with the First Fleet, they brought the house mouse (Mus domesticus) with them.
In the south-eastern Australian grain belt, which stretches from the South Australia–Victoria border to the Darling Downs in southeast Queensland, mouse population levels are normally quite low. However, favourable seasonal conditions can trigger extensive breeding. Mouse plagues now erupt in these regions on average every three years. An estimated 100,000 to 500,000 hectares of grain crops is affected each year.
Mouse breeding facts
- Mice breed from August to May (in the Southern Hemisphere)
- Mice commence breeding from six to eight weeks of age
- Female mice are pregnant for 19 days and remate 1-3 days after giving birth
- Litters usually contain five to six babies, but it can be as high as nine to ten during the lead up to a plague
- One breeding pair of mice and their offspring can produce 500 mice in just 21 weeks
- During a typical plague in southern Australia, mouse densities of 1000 per hectare are common
Invasive Animals Cooperative Research Centre
These plagues cause massive disruption to communities and losses to farmers in Australia of around $36 million annually in lost agricultural production and control.
Mouse plagues don’t just cause economic problems. Swarms of mice invade households, hospitals, livestock pens, food storage and other facilities, causing significant damage to infrastructure. They consume large quantities of grain and contaminate grain shipments with their faeces. They pose a major threat to health and welfare, inflicting stress on humans and livestock.
Traditional controls
Mice have traditionally been controlled using trapping and powerful poisons. However, these can only provide limited control and the poisons can also kill dogs and cats, as well as native predatory animals that eat poisoned mice.
Biotechnology controls
Researchers tried to use biotechnology to develop a new approach to controlling mice through limiting their reproduction. The Invasive Animals CRC (formerly the Pest Animals Control CRC) investigated the feasibility of immunocontraception for mice. The process involves fooling the body into thinking that certain proteins found on mouse egg cells are foreign. The body's immune system produces antibodies that bind on to these proteins, preventing pregnancy.
The researchers genetically modified a virus that occurs naturally in mouse populations — mouse cytomegalovirus (MCMV) — which successfully sterilised female mice. However, the modified virus was unable to transmit naturally through a population. The long time scale and projected high cost of further research meant that the project had to be abandoned.
Instead, research has returned to focusing on baiting programs in intensive crops, with trials of baits with reduced risks of secondary poisoning and that are safer for pesticide workers.
General information on the introduced house mouse is available at the National Feral Animal Control Program: http://www.feral.org.au/species/rodent.asp
Read more about the research into immunocontraception for mice at the Invasive Animals CRC: http://www.invasiveanimals.com/invasive-animals/rats-mice/index.html