Population recovery of common brushtail possums after local depopulation

Abstract

Brushtail possums (Trichosurus vulpecula) were live-trapped for two years prior to and following depopulation in two ~6-ha areas of native forest in New Zealand. The populations had recovered to 55% of the original density at one site and 40% of the original density at the other site, two years after the depopulation. The post-removal populations responded to reduced density with a higher proportion of females breeding, higher survival rate of young, and less seasonal fluctuation in body condition. The initial recolonisation was probably mainly due to surrounding animals shifting their ranges into the depopulated area, rather than long-range dispersal, which resulted in an even sex ratio in the recovering populations. The greater proportion of adult males in the post-removal populations is likely to increase sexual contact rates for females. This would enhance the dissemination of a viral-vectored biological control agent through the population, when used as part of an integrated control program.