Population ecology and the control of pests.

An understanding of the factors responsible for the numbers of animals observed is essential for effective integrated control of pests. An ecological study need not, however, be complete for it to be useful; many incomplete such studies have led to clues that have served as important guides in control programmes. However, it is important that the study of animal numbers be undertaken with a completely general model in mind. Some ecological models suggested are too restricted to be generally applicable. The generalized model proposed by the author is based on the proposition that the chance to survive and multiply depends on environment, which may be effectively studied as having five components: resources, climate, numbers of the same species, numbers of other species, and hazards. Any of these components may be important and different components may be important at different times in the history of an animal population.Populations are most often limited by inaccessibility of resources and by the shortage of time during which the environment is favourable to an increase in numbers. An understanding of these factors suggests ways in which numbers may be further restricted. The student of pest control must determine if such ways can be economically used in a programme of integrated control.