Genetic Options for the Control of Invasive Vertebrate Pests: Prospects and Constraints

Conventional methods for the control of invasive pests are generally effective only on small-space scales or short-time frames. For most well established pest populations, longer-term efforts to manage the problem have been largely abandoned. I examine the potential of using “autocidal” genetic techniques to control terrestrial vertebrate pests, based on the inheritance through males of transgenes that either sterilise females or convert them into functional males (“daughterless”). Simulation analysis of two high profile pest species, the cane toad (Bufo marinus) in Australia and brown rats (Rattus norvegicus) in an urban environment, using realistic parameters, suggests that virtual eradication could be achieved at apparently realistic stocking rates within 100 years for toads, and in less than 20 years for rats. The essential genetic requirements for autocidal technology (the ability to genetically transform the pest, genes that when blocked cause sex-specific infertility or sex change, and a means of shutting off the construct for breeding purposes) have already been demonstrated in rodents and are likely to be available in other pests, based on broad conservatism of genetic mechanisms of sex differentiation in vertebrates. Hence, there appear to be no major logistical or technical impediments to developing a genetic control program against many pest species. However, the models also indicate that a recombinant pest control program would be difficult against species whose populations are under strong density dependent regulation or are so large that absolutely high numbers of carriers need to be stocked to achieve control. More potent genetic options than those modelled could be feasible, but their use needs to be tested against public acceptability, due to the apparently higher risk they pose for non-target populations and species.