Black Rats (Rattus rattus) accompanied the first European travellers to Australia. They are now found in many near-coastal regions and also on some islands. In the Northern Territory they are largely restricted to the Top End, where they are common around some urban areas, especially in the Darwin region. They appear to have increased their range and abundance across the Top End over the last two decades, extending well away from settlements, typically in riparian vegetation. However, in arid areas they are only found in association with human habitation.
House Mice (Mus musculus) are abundant around settlements and in agricultural areas. In arid and semi-arid areas of the Northern Territory House Mice can also be seasonally abundant away from human habitation.
Black Rats are recognised as a Key Threatening Process on islands, where they have contributed to the extinction of many species. Being omnivorous, they will prey on any small animal they come across, including the eggs and young of threatened species. Black Rats have been found in the Victoria River region in the habitat of the Purple-crowned Fairy-wren, so predation of this species is likely. Rats and Mice are predators of land snails, and are a particular concern for Desmond's Land Snail and Fitzroy Land Snail. House Mice prey upon young birds and impact upon native vegetation through seed predation.
Rats and Mice also compete with native animals for food, particularly through depleting seed banks, and carry diseases that can affect both native mammals and humans. An increase in disease or predation associated with the expansion of Black Rats across the Top End during the last two decades, is one theory possibly contributing to the decline of some native mammals over the same period.
The best way to control Rats and Mice is to remove their food supply by disposing of and burying rubbish properly. Black Rats have been eradicated from 39 Australian islands, and 160 islands worldwide. Poisons that prevent blood clotting are the ones most commonly used to eliminate Rats and Mice. But these poisons have serious problems, and can cause high death rates among non-target species, especially with broadscale baiting. They also persist in the environment. Zinc phosphide (sold as RATTOFF® or MOUSEOFF®) is an effective control agent that is less environmentally damaging than are most other poisons used for rodent control.