EFFECTS OF VACCINATION AGAINST GONADOTROPIN-RELEASING-HORMONE (GNRH) ON THE SOCIAL-STATUS OF BRUSHTAIL POSSUMS IN CAPTIVITY

Options for the biological control of brushtail possums (Trichosurus v ulpecula) are being evaluated in the hope of finding a cost-effective, long-term solution to the problem of reducing numbers of possums as h osts of bovine tuberculosis and as threats to conservation values. Met hods of inhibiting possum reproduction by affecting sex steroid levers are among the options. However, this may result in behavioural change s. In some species, a loss of status by dominant animals allows subord inates to breed more successfully. This paper describes how social hie rarchies in captive groups of possums are affected by vaccination of d ominant females against gonadotrophin-releasing hormone (GnRH) to bloc k all centrally controlled steroid hormone release. Ten groups consist ing of two females and one male were established in pens, and the domi nance status of each animal was measured by recording the outcome of s ocial interactions during monthly observations. The dominant female in each pen was vaccinated against GnRH with a series of three immunisat ions. Social hierarchies remained unchanged over the 2-4 months after vaccination of the dominant females. We therefore conclude that method s of biological control that disrupt sex steroid production could be c onsidered for possum control once these findings are confirmed by simi lar observations on wild possums.