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.