Silver (1995), drawing on detailed genetic analysis, lists 8 true species in the Mus subgenus plus 4 morphologically and biochemically distinct Mus musculus subspecies that together form an M. musculus species group. These are Mus mus musculus, M. m. domesticus, M. m. castaneus, and M. m. bactrianus. He relegates M. m. molossinus, found throughout Japan, to faux-species status as it has been found to be a hybrid between M. m. musculus and M. m. castaneus. Furthermore, the genetic evidence supports the Indian subcontinent as the centre of radiation for the M. musculus species group, M. m. bactrianus being the founder population. The members of the M. musculus group would have occupied non-overlapping ranges within the Indian subcontinent until Neolithic human population expansion and migration approximately 10,000 yrs BP facilitated their dispersal.

The two species found in Europe - M. m. musculus and M. m. domesticus - accompanied humans migrating into the area approximately 4,000 yrs BP. It is predominantly these two species that have become invasive throughout the world, primarily aided by past European colonial expansion. Recently genetic methods have been used to trace the colonisation history on mice in New Zealand and the United Kindom (Searle et al. 2008a, 2008b).

It has been estimated that in the USA seven mice are transported per 100 tonnes of grain and 70 per 100 tonnes of hay or straw. In one year 550,000 tonnes of hay and straw were exported from the USA potentially containing many thousands of house mice (Baker 1994 cited in Pocock et al. 2005).

Mice have also been implicated in extirpations and/or extinctions of indigenous species in ecosystems they have invaded and colonised which are outside their natural range. Angel et al (2009) reviewed mouse impacts on islands in the Southern Ocean and found that mice had negative impacts on plants, invertebrates, land birds and sea birds. An important finding of this review is that when mice are the only introduced species on an island their behaviour is more similar to that of rats and has a much larger impact on the native ecosystem. When mice are part of a complex of invasive species their densities are suppressed and their impacts are not as great. On Juan de Nova Island in the Mozambique Channel cats have a major impact on the sooty tern (Sterna fuscata) colonies through predation. Peck et al (2008) found that introduced mice and rats supported the cat population through the tern non-breeding season meaning the cat population was large throughout the year. This effect is known as hyperpredation and the authors suggest removing mice andsand rats may help preserve the tern colony.

\r\nRecent research and video evidence from Gough Island in the South Atlantic Ocean, has shown conclusively that mice are responsible for widespread breeding failures and that predation of seabird chicks by mice occurs at levels that are probably driving population decreases. Please follow this link to view the video Wanless mouse attack on albatross chick recorded by Ross Wanless and Andrea Angel on Gough Island (Viewer discretion is advised).
Please follow this link for terms and conditions of use of the video.

Species affected on Gough Island include the 'Crtically endangered (CR)' Tristan albatross (see Diomedea dabbenena) and the 'Endangered (EN)' Atlantic petrel (see Pterodroma incerta). Other species believed to be subject to mouse predation include the two winter breeders - the 'Near Threatened (NT)' grey petrel (see Procellaria cinerea) and the great-winged petrels (see Pterodroma macroptera) (Wanless et al. 2007). M. musculus may pose the greatest present threat to the 'Critically endangered (CR)' Gough bunting (see Rowettia goughensis) through competition and predation (Birdlife International, 2004).

A study of seed predation by mice in a New Zealand forest found that mice were able to consume almost the entire seed crop of some species therefore having important implications for tree population dynamics (Wilson et al 2007). Another study in New Zealand found that mice were predating upon lizards and that adults were more susceptible than juveniles (Newman 1994).

Preventative measures: House mice are able to stow away in very small spaces so there is a constant threat of invasion or reinvasion. Visitors to areas that are at risk of mouse invasion should be encouraged to check all baggage and pockets for mice before heading to such places. Mouse free areas that are considered at risk of invasion should implement a programme of regular monitoring to identify mouse invasions early.

Chemical: House mice have been successfully eradicated from 28 islands worldwide. In all these cases some form of anticoagulant poison was used (MacKay et al. 2007). Brodifacoum was the most commonly used poison, other successful attempts used pindone, warfarin, bromodiolone and floccoumafen. Brodifacoum is a very widely used toxin but there are some concerns about it building up in ecosystems (Hoare and Hare, 2006). Fisher (2005) discusses the susceptibility of mice to a variety of anticoagulant poisons; Morriss et al. (2008) updates this study by investigating factors that affect the palatability of different baits to house mice and rat species.

Biological: Virally vectored immunocontraception using a modified murine cytomegalovirus (MCMV) has been investigated in Australia to control mouse plagues in the grain growing regions but results are not promising. Viral transmission rates are too slow to effectively control fertility on the population (Arthur et al. 2009). A review of fertility control in rodents is available (Jacob et al. 2010).

Integrated management: The abundance of M. musculus will increase dramatically where a significant number of rats are removed from an area, perhaps due to an improved food supply or a release from predation pressure (Caut et al. 2007, Witmer et al. 2007). It is important to attempt to remove mice at the same time as rats to prevent large populations of mice appearing following rat removal.