Temporal trends in use of fauna-friendly underpasses and overpasses

Abstract

The impact of roads on local biodiversity is a major issue associated with urbanisation. A major arterial road in the southern suburbs of Brisbane, south-east Queensland, was upgraded in 2004–05 from two to four lanes. In an attempt to minimise the impact of the larger road on local wildlife populations, a range of fauna crossing structures were constructed at the site. Monitoring of road-kill was undertaken for 4 months before construction and after the completion of construction. Assessment of the use of two underpasses and a large overpass (‘land-bridge’) started 6 months after construction using sand tracking in underpasses and scat sampling on the land-bridge. An initial 26-week period of intensive monitoring was undertaken from August 2005 to February 2006 followed by monthly monitoring from June 2006 to June 2007. On average, 1–5 tracks per day were detected in the underpasses at the start of the survey, increasing steadily to ~42 tracks per day by February 2006. The monthly survey showed regular use of the underpasses by a wide range of species and species-groups, the most abundant being ‘rodents’, most likely Rattus species, both native and introduced. The land-bridge was also used continuously by three species of macropod (red-necked wallaby, Macropus rufogriseus; swamp wallaby, Wallabia bicolor; and eastern grey kangaroo, Macropus giganteus) with brown hare (Lepus capensis) becoming increasingly common in summer 2006. The exclusion fencing was extremely effective in preventing most road-kill, at least of larger species, except following human-related breaches in the fence.