Immunocontraception as a potential control method of wild rodent populations

Rodents have the capacity to periodically reach very high numbers in agricultural landscapes, reducing agricultural production, and causing considerable environmental and social problems for farmers and their families. Such rodent problems occur worldwide and have a long history. Currently mortality enhancing agents (mainly poisons) are the principal method of rodent control. This approach raises environmental, ethical and humane issues, and ignores the inherent high capacity for increase in these species. We argue that it is more appropriate to reduce reproduction than increase mortality. This paper uses house mice in Australia as a case study to explore fertility reduc tion as a potential alternative to conventional methods of control. In particular, the question of what level of fertility control is required to have a significant effect on population growth is discussed. A computer simulation, based on the life-history strategies of house mice, examined the effect of different levels of fertility control on mouse population dynamics. This simulation provides a reference for future studies of confined populations of mice used to test the effects of fertility control, refines the design of these experiments and identifies the type of data needed to be collected. Immunocontraception, the process of inducing the body's immune system to attack its own reproductive cells, is suggested as a method for reducing fertility in rodent populations. The advantages and disadvantages of immunocontraception over mortality-enhancing agents are discussed, as are the potential impacts of social structure on the efficacy of immunocontraception and the possible application of this control method to other rodent pest situations, particularly rodent pest problems in Africa.