Effects of a Rainforest Road on Movements of Small Mammals: Mechanisms and Implications.

Abstract

Live-trapping was used to study the effects of a road on the movements of 4 species of terrestrial and scansorial mammals at 4 sites in upland vine-forest at Mt. Spec, N. Queensland, in February, March, May, June and August 1989. The road consisted of a 4-m wide bitumen strip at all sites; it was flanked by 1-m wide shoulders on each side at 2 sites and 4-m wide shoulders on each side at the other 2 sites. When baited traps were set on both sides of the road during grid-trapping, the road crossing rate of Uromys caudimaculatus (20% of recorded movements) was significantly greater than that of Rattus fuscipes and Antechinus flavipes (1.8% and 5.2% of movements, respectively). Melomys cervinipes was not recorded crossing the road under these conditions. R. fuscipes, M. cervinipes and A. flavipes were induced to cross the road more often when baited traps were placed on only one side of the road. The crossing rate of R. fuscipes was increased by translocating individuals across the road. The inhibition of movement caused by roads was attributed to psychological and/or sociological characteristics of the species and/or the individual rather than to the effect of a physical barrier. The results also indicate that the threat of genetic isolation of populations of these species dissected by roads less than 12 m wide is slight. However, less mobile species or wider roads may result in genetic isolation. Measures are suggested to alleviate the barrier effects of roads.