In order to provide a better understanding of the suggested management procedures, some general characteristics of rodent pests will now be described.
There are about 1,700 species of rodents, only a few of which are considered pests; even fewer infest cities and villages, buildings or stores. Some common examples are:
Name |
Distribution |
Rattus rattus (Black or roof rat) Rattus norvegicus (Brown or Norway rat) Mus muscuslus (House mouse) |
Cosmopolitan |
Bandicota bengalensis (Bandicoot rat) |
Southern Asia |
Calomys, Akodon, Oryzomys, Sigmodon |
South America |
Mastomys, Tatera, Acomys, Arvicanthis |
Africa |
Those that are pests have two important characteristics in common.
Prolific breeders: These species have many young per litter or several litters in one season, or both. This enables them to rapidly build up very large populations, generally when the crop is maturing or stores are filled with produce. However, the population does not explode overnight. One generation takes four to six or even more weeks to develop. With proper monitoring, appropriate management measures (i.e. removal of rubbish, repairs, poison baiting) can be taken in time and can prevent or reduce losses.
Generalists: Most rodent pests can feed on a variety of foods including grains, fruit, vegetables, even meat and eggs, all types of processed food items and of course organic garbage or refuse. They can live in villages and move into surrounding fields. The most widespread rodent pests - especially those infesting stores and buildings - are highly adapted to all types of human activities and are rarely found in native or natural vegetation.
Rodent pests are also fairly mobile and quickly re-infest areas where they have been eliminated by control measures. After harvest, they move from surrounding fields into villages. However, this does not mean, as is often thought, that they move for kilometres. Populations build up simultaneously over large areas with similar, favourable conditions.
For management purposes, it is important to realise that pest rodents closely associated with human activities are nervous or shy about new objects (such as bait or traps) in their environment. They prefer to use the same runs and do not like regular disturbance. Disturbance has a negative impact on their breeding success. In general, rodents require two factors for successful breeding: food and shelter. While it is not practical to remove the food from stores, access can be made difficult and shelter and refuse can be removed to a large extent.