From the pens to the field: real-world wildlife contraception

There are only two nonlethal approaches with which to manage wildlife populations: remove excess individuals or decrease reproductive rates. In the case of wild horse management, the latter has already been shown to be a more humane and less costly approach. Contraception has been known for many years to be effective in wild horses with regard to both fertility and population alteration. Field testing under real-world management situations is a critical aspect of wildlife contraception assessment. Field testing also requires documentation to justify eventual large-scale use of fertility control in population management. Furthermore, it is likely that full support by the managing agencies and acceptance of fertility control by the public will not occur until success has been demonstrated at the population level in the field. Because the transition from laboratory and captive animal trials to the real world of field research and testing of management potential in free-ranging wildlife is both essential and difficult, we identify considerations for optimizing success in the field, especially for controlling wild horse and white-tailed deer populations. This study identified the following categories for assessment: 1) field-specific logistics and tactics (including access to and identification of horses, censuses, pregnancy testing, and behavior monitoring), 2) training of field personnel and managers (including vaccine biology, preparation and delivery, and basic field methodology), 3) essential field considerations for enabling management (including population variables, environmental variables, and modeling), and 4) pitfalls of field contraception. In this assessment, we will highlight the capability for coincident pursuit of research and management and will explore field considerations applicable to many species where fertility control has potential as a management tool.