IENE 2016

The ability to predict the conditions under which certain species of conservation concern cross linear infrastructure (i.e. roads, rail), is an important step toward instituting management approaches aimed at maintaining population viability and integrity. In south-east Queensland, Australia, rapid urban development and related consequences including habitat loss, fragmentation and increasing vehicle-related mortality has significantly contributed to a dramatic decline in local koala populations, which together has led to them being listed as a threatened species in Queensland. Research to determine the success of wildlife-road mitigation works has demonstrated clear benefits in enabling safe passage across roads for many species. However the construction costs of eco-infrastructure that can effectively meet the need for all species to move freely across impacted landscapes is usually both prohibitive and unrealistic at scales commensurate with the problem. Therefore, a better understanding of which individuals that are most likely to undertake crossings should allow resources to be focussed on locations that maximise benefits.  This study attempted to do just that, by examining the probability of individual koalas within a set of sub-populations that actually crossed roads within a region. We modelled the number of individual koalas that crossed roads, and the frequency with which they did so, at six sites. We explored the influence of potential predictor variables in models including: age; sex; weight; and distance of first capture point from roads of interest. We grouped all road crossing events including those that occurred both over any major roads of interest or those involving the use of eco-structures.  Our assumption was koalas that crossed using eco-structures may have also been inclined to cross roads if such structures were not available, providing an initial picture of road crossing risk. We found koalas were disproportionately more likely to cross roads if first captured within a distance of 100m of a road of interest.    We also established that road crossing activity was limited to a relatively small subset of individuals, with only 18/51 (~35%) koalas studied determined to have ever crossed a road of interest. Our results are preliminary, but suggest that a better understanding road crossing behaviour of koalas will have significance for road agencies seeking to mitigate road strike for this species when designing, upgrading or building new roads.

Movie