Rat problems in Australia

Rat problems in Australia

rattus Sordidus

Rattus Sordidus

There are currently over 60 described species of rats in Australia, and they occupy a wide range of the habitats across the country. The majority of these are native species; however two rats (Black Rat and Brown Rat) are introduced species that have rapidly adjusted to Australian conditions.

The widespread and abundant Black Rat (or Roof Rat, responsible for London's Bubonic Plague in 1665), is a commensal rodent that is usually found in disturbed or degraded environments. It is the rat most commonly observed in cities and towns, and is often responsible for the infestation of houses, sheds, warehouses and storages.


Most rats are granivorous (primarily seed-eaters), with an herbivorous diet the next most common form. Generally, rats are omnivores and will consume a range of food items depending on availability.


Human intervention, in the form of clearing unsuitable habitats and planting cereal and other food crops, increases the optimal habitat and food resources for rats. An example is the native Canefield Rat, a grassland species that has increased in range due to the conversion of native rainforest habitats (unsuitable habitat) to sugarcane, where the soft soil and abundant food and shelter has enabled them to build up to "pest" levels, and hence cause crop damage.

Rat Biology

The Black and Brown rats, together with about six native rats, have a rapid life-strategy based on high birth rates, short life-spans and high death rates.

The large litters (up to 12 per litter) are born at a young age (approximately 21 day gestation), have minimal parental care, and are independent at an early age (21 days until weaned). These individuals are generally sexually mature and ready to breed at around 10 weeks.

These rats are capable of producing ten or more young every three weeks under ideal conditions. This breeding base can lead to rapid overpopulation and allows them to exploit optimal conditions, causing damage in cropping situations if population numbers become high.

The majority of native rats, however, are slow-breeding animals, with small litter sizes, regular breeding seasons, longer gestation and weaning periods, and lower juvenile mortality rates. These rats generally occur in non-cropping habitats and are therefore not considered to be "pest" species.

Temperature and food supply are known to be limiting factors for breeding, and often the season is extended when the temperature is moderate, and food readily available.

Rats require the protein in weed and grass seeds to maintain breeding condition, and early seed production can lead to an early commencement of the breeding season. Suppression of weed and grass growth in-crop is required to restrict the available food source and habitat area for rat breeding and development.

Rat infestations in crops

Cane crop is an ideal habitat for rodents

The cane crop is an ideal habitat for rodents

Local and introduced species of rats have the potential to breed quickly and infest crops and food storages, where they cause serious economic damage. This is a major international problem and represents one of the most significant causes of lost or spoilt food supply worldwide.

Eruptions of serious rat infestations in Australia are not easy to predict and the circumstances leading to infestations of crops are not fully understood. In some crops, the development of significant rat numbers may occur only once or twice per decade. In other crops, such as tropical sugarcane, conditions are favourable for rat infestations in most seasons. Even so, the severity of infestation can vary widely between properties and between areas in any one season. Because of this variability, and the unpredictable occurrence of infestations, the control of some types of rodents can be difficult. Animal Control Technologies specialises in tailoring technical solutions to specific rodent problems.

Monitoring for the presence of rodents is essential.

Animal Control Technologies (Australia) Pty Ltd
46-50 Freight Drive
Somerton, Victoria, 3062
Telephone +61 3 9308 9688
Fax +61 3 9308 9622

E-mail: enquiries@animalcontrol.com.au