Population models and immunocontraceptive vaccines for managing outbreaking rodent species

• Chinese Academy of Science, China

Plagues of mice in Australia and Brandt's vole in China erupt periodically, causing significant damage. In grassland ecosystems these plagues can exacerbate damage and deterioration caused by grazing livestock. By utilising expertise in ecology, reproductive biology and molecular biology of rodents the project scientists undertook population studies of both rodents and assessed the feasibility of fertility controls for their management in grassland and cereal production systems. They also determined the potential to use an immunocontraceptive vaccine for Brandt's vole.

The project aimed to predict the occurrence of high densities of Brandt's vole in Inner Mongolia and the house mouse in southeastern Australia, also to assess the feasibility of fertility control for the management of rodents in grassland and cropland. This involved studies to understand more about the female reproductive biology of both species and to initiate the development of an immunocontraceptive vaccine for Brandt's vole.

The project examined two key aspects of rodent management: 1) the development of population models for improving the reliability of predictions for outbreaks of house mice and Brandt's voles, as well as prediction of the value of fertility control compared with existing techniques based on non-specific rodenticides, and 2) the assessment of immunocontraception as a species-specific, cost-effective, humane and environmentally benign method of control for Brandt's vole. The modeling was needed to assess the impact of fertility control on the population level and to design future field trials and integration into agricultural production systems, and measure their ability to impair the fertility of individual animals. These activities laid the foundation for the next generation of rodent control agents.

Progress in the work on population modeling and predictions was highly satisfactory. For the Chinese the results highlighted the need to pursue integrated management of livestock and rodents. As well, computer simulations predicted that fertility control could be as effective (and in some cases more effective) in managing Brandt's vole than lethal control with rodenticides.
In Australia the project resulted in important advances in understanding the changes in demographic parameters that lead to the development and eventual collapse of mouse plagues. However there is still much to learn about the ecological processes involved. The availability of substantial sets of earlier demographic data from both China and Australia greatly assisted the execution of this aspect of the project.
Assessment of the feasibility of fertility control of Brandt's vole was also successful, with one vole reproductive antigen showing capacity to induce infertility in captive female voles. Trials to assess potential antigens were hampered by the seasonal breeding pattern of the vole, but the results indicated that further studies to develop better management strategies and tools for rodent control are warranted both in the field and the laboratory.