Author:
Efford Murray,Warburton Bruce,Spencer Nick
Abstract
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 ‘vacuum effect’ –
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–1 inside the removal area and 16
ha–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–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.
Subject
Management, Monitoring, Policy and Law,Ecology, Evolution, Behavior and Systematics
Cited by
55 articles.
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