Social dominance and breeding success in captive brushtail possums, Trichosurus vulpecula

Abstract

The brushtail possum (Trichosurus vulpecula) is New Zealand's most important mammal pest. Options for the biological control of possums are being evaluated, particularly fertility control. The functions of social dominance hierarchies in possums have not been determined, but in many species dominant males breed more successfully than subordinates. This paper describes the effect on breeding success in captive groups of possums of vasectomising the dominant male. Dominance was measured by recording the outcome of social interactions during monthly observations. In groups of two male and two female brushtail possums, the dominant male was vasectomised (n = 7) or left untreated (n = 5). Five other groups with one male and two females were used as additional controls. In the groups where the dominant male was vasectomised, its dominance status remained unchanged after treatment but there were no further births, whereas young continued to be born in pens where males were untreated. At least in captivity, dominant males are therefore capable of behaviourally or physiologically inhibiting reproduction by subordinate males. This is the first evidence for such an effect in possums.

Keywords:

• brushtail possums
• Trichosurus vulpecula
• dominance
• social behaviour
• reproduction
• fertility control