Movements and habitat preferences of pests help to improve population control: the case of common brushtail possums in a New Zealand dryland ecosystem

BACKGROUND Introduced brushtail possums are controlled in New Zealand to mitigate their spread of bovine tuberculosis in livestock. Given the low rainfall and extreme variation in seasonal temperatures in dryland areas of the South Island, the habitats of possums in these areas differ in many respects from those in the rest of New Zealand. We investigated the movements and habitat preferences of possums at two dryland sites to identify where they aggregate following population control by using GPS collars and cards chewed by possums. At one site, possum numbers were reduced from high levels by 65%, and at the other site, possums had already been reduced to low levels for some time beforehand but were further reduced to maintain them at low levels. This resulted in different possum densities. RESULTS Possum home ranges were about 3 times smaller at the higher‐density site, but average ranges expanded by 27% following initial control. Home ranges were already large at the lower‐density site but did not expand further after maintenance control. No preference for habitat types was apparent at the higher‐density site, but at the lower‐density site possums selected rock and shrubby habitats and avoided open grassy areas. CONCLUSIONS Home range sizes and habitat preferences were density dependent: the lower the density, the larger was the home range; and habitat preferences were highly variable between individuals, but less so for possums at low density. Preference for shrubs and rocks is likely to benefit population control if population control devices are focused on these habitat types. © 2016 Society of Chemical Industry