Changes in possum spatial behaviour following a control operation: implications for conservation and bovine tuberculosis management

Abstract

The Australian brushtail possum (Trichosurus vulpecula) was first introduced into New Zealand in the 1800s to establish a fur trade. As time has progressed, it has become apparent that the possum has a number of adverse effects on native flora and fauna due to its opportunistic and varied diet. In addition, the possum is also responsible for transmitting bovine tuberculosis (Mycobacterium bovis) to cattle and deer. Consequently, numerous control operations are undertaken within New Zealand at a cost of millions of dollars, for both conservation and bovine tuberculosis management. The goal of these operations is to significantly reduce population densities, but it is inevitable that some individuals survive. It is unknown whether these survivors change their spatial behaviour in response to lower population densities. Current follow-up control methods generally do not account for any changes in spatial behaviour following initial control, largely due to limited research regarding this issue. If spatial behaviour does change, this may be inhibiting our ability to manage this species efficiently for conservation purposes and to eliminate areas of persistent bovine tuberculosis infection. Consequently, our research investigated whether possum home-range characteristics, pasture use and den-site use, changed following an experimental control operation in a forest fragment in Mid Canterbury. Possums were fitted with collars containing Global Positioning System and VHF devices, to establish movement patterns through space and time. Several movement parameters changed following control, such as home-range size and home-range overlap. This research highlights the need to update national and local control strategies to account for this change in behaviour. For example, the effectiveness of spatial models predicting the transmission of bovine tuberculosis would be increased by incorporating the recorded changes in home-range size and overlap following initial control.