Eradicating invasive rodents from islands can help restore these rare and unique ecosystems. However, there are many problems with the conventional methods of eradicating invasive house mice (Mus musculus). Recent genetic engineering technologies offer an interesting new alternative. One proposed method, the t-Sry mouse, involves modifying a mouse to carry an engineered gene construct that would cause a majority of its offspring to be male, many of which would be sterile. Releasing these genetically engineered mice to interbreed with an invasive mouse population could reduce the number of fertile female mice over time. Eventually, without any females to produce offspring, the population would be eradicated. We construct and analyze a population model to determine how efficiently this newly proposed engineered gene construct could spread through and eradicate a population. We also use this model to estimate what release strategies could minimize the time to eradication, the number of mice being released, and the ecological pressure on the rest of the ecosystem.
Results/Conclusions
In most cases, t-Sry mice can eradicate an invasive population if they are repeatedly released into a population above a certain threshold. This threshold can be decreased if the fitness cost to carrying the t-Sry construct is reduced. If t-Sry mice could have a large fitness advantage, the construct could theoretically spread and eradicate an entire population without repeated releases. We also find that there is no optimal release strategy that minimizes all potential ecological impacts. High release rates of t-Sry mice with greater fitness can eradicate a population of invasive mice relatively quickly, but this results in a large increase in the density of an ecologically disruptive population. A lower release rate and higher fitness cost, on the other hand, can reduce the maximum population density of mice throughout the eradication; however, eradication might then take several additional years to complete. Thus, there is a tradeoff between the duration and intensity of the transient ecological impacts of mouse eradication with genetic engineering.