
%0 Journal Article
%A Efford, Murray 
%A Warburton, Bruce 
%A Spencer, Nick 
%T Home-range changes by brushtail possums in response to control
%J Wildlife Research
%D 2000/03/29
%V 27
%N 2
%P 117-127
%K 
%R https://doi.org/10.1071/WR99005
%U https://www.publish.csiro.au/paper/WR99005 
%X Common brushtail possums (Trichosurus vulpecula) are intractable pests in New Zealand. The effectiveness of local control can be limited by immigration, some of which has been attributed to a &#8216;vacuum effect&#8217; &#8211; directed movements induced by the control itself. To characterise the vacuum effect we examined changes in the home ranges of trapped possums following control in a 6-ha block at one end of a 13-ha forest patch on farmland near Dunedin, New Zealand. We also monitored a sample of possums by radio-telemetry. After control, the density was 3 ha&#8211;1 inside the removal area and 16 ha&#8211;1 outside. During the year after the removal, 29% of possums within 100 m of the boundary of the removal area (n = 38) shifted their range centre at least 50 m towards it. The effect diminished rapidly with distance: only 1 of 28 animals moved more than 200 m from the boundary. The size of the previous range was a significant predictor of movement among males, but this may be partly a sampling artifact. We measured a net flux of 69 possums km&#8211;1 across the boundary in the 12 months after control, and possums settled on average 44 6.9 m inside the boundary. The vacuum effect in brushtail possums appears largely confined to home-range adjustments by individuals with ranges overlapping the area of reduced density. This limits its potential role in population recovery. 
