Discouraging wildlife from entering buildings: A case study of the common brushtail possum (Trichosurus vulpecula)

Abstract

Interactions between humans and wildlife often occur in human settlements (i.e., urban, suburban, exurban and rural areas). Human-wildlife interactions can lead to conflicts when the behaviours of wildlife negatively impact human interests. The common brushtail possum (Trichosurus vulpecula) is a protected native species in Australia that, in its natural habitat, typically uses hollows in trees as places to den during the day. In urban areas the species can use cavities in buildings as den sites and cause considerable damage or disruption to building occupants. Although several strategies to discourage this species from entering buildings have been recommended, few have been evaluated empirically. In this research I aim to contribute to the knowledge on how to effectively discourage the common brushtail possum from entering buildings. I aim to identify landscaping and building attributes that influence building selection by the common brushtail possum which can be manipulated to reduce the chance of having possum-related incidents in buildings. I collated reports of possum-related incidents in 134 buildings over 12 years on the campus of The Australian National University (ANU). I used generalised linear modelling (GLM) to identify significant associations between the number of reported possum-related incidents in buildings and a range of landscaping and building attributes. I found that suitable habitat surrounding buildings (e.g., larger tree and shrub canopy cover), suitable access to building roofs (e.g. trees with canopy overhanging buildings) and weak points in building roofs (e.g., areas around parapets (walls extending above the roof) and structures penetrating from the roof) make buildings more vulnerable to occupancy by the common brushtail possum. These landscaping and building attributes could be manipulated to discourage this species from entering buildings. One of the results from the analysis of building selection by this species suggested a positive association between the number of reported possum-related incidents in buildings and the length of tree canopy overhanging buildings. Therefore, I tested the effectiveness of installing tree guards on overhanging trees in discouraging the common brushtail possum from accessing buildings. I used a generalised linear mixed model (GLMM) to evaluate the difference in possum activity on three buildings before and after the installation of tree guards on overhanging trees. The results from this experiment indicated that possum activity declined after the installation of tree guards but the decline was not significant. This could be because the common brushtail possum could jump over some tree guards via adjacent tree branches or other structures (e.g., railings) and overhanging trees may not be the sole means this species uses to access the roofs of buildings. My results provide clues for managing existing buildings and designing new buildings in a way that may reduce the likelihood of occupancy by hollow-dependent species such as the common brushtail possum. My research also demonstrates how an analysis of factors that influence building selection by problem animals can help identify possible management solutions, and how building maintenance records can be used to address human-wildlife conflict over time. Show more