Road upgrade, road mortality and remedial measures: impacts on a population of eastern quolls and Tasmanian devils

Abstract

The impact of road mortality on local populations of wildlife has rarely been quantified. In June 1991, the access road into the northern end of the Cradle Mountain – Lake St Clair National Park in Tasmania was widened and sealed. This occurred part-way through an ecological study of the dasyurid carnivore guild, during which populations were being monitored. In 17 months, the resident population of 19 eastern quolls became extinct and the devil population, of 39 individuals, halved. Concurrently, there was a dramatic increase in the number of road-kills. The main causal factor was probably an increase in modal speed of about 20 km h–1 and a greater increase in maximum speed. Measures were implemented to reduce the incidence of vehicle/wildlife collisions. Measures directed at people included physically slowing traffic speed (using ‘slow points’) and increasing driver awareness (signs and pamphlets). Those directed at wildlife included deterring wildlife from crossing the road in the path of approaching vehicles (wildlife reflectors), and encouraging escape off the road (ramps across gutters and banks, and pipes for shelter). The ‘slow points’ were effective in reducing vehicle speeds by 20 km h–1. Wildlife used the ramps and pipes. The eastern quoll population was re-establishing within six months, and after two years, had recovered to 50% of its former level. There was some indication that devil populations were recovering.