Individuals matter: predicting koala road crossing behaviour in south-east Queensland

Abstract

The ability to predict the frequency with which koalas (Phascolarctos cinereus) cross roads is an important step in developing mitigation strategies aimed at maintaining metapopulation viability for this species. In south-east Queensland, Australia, rapid urban development, including fragmentation and vehicle-related mortality, has contributed to a dramatic decline in local koala populations. Assessment of wildlife crossing structures that mitigates the impact of roads demonstrates these to be beneficial for many species. However, building enough structures to enable animals to move freely across impacted landscapes may be prohibitive in complex urban landscapes. The focus for this study was to consider the role of differing characteristics for species at risk. We examined the frequency of road crossings by individual koalas among six subpopulations in south-east Queensland. We explored the influence of potential predictor variables including: age, sex, and distance from roads. We established that road crossings were limited to a subset of individuals, with only 18 of 51 (~35%) koalas studied ever crossing a road. We found that koalas were disproportionately more likely to cross a road if they had initially been found within a distance of 100 m of that road. Males were more likely to cross roads than females, as were koalas aged less than five years. We suggest that successful wildlife road mitigation can be improved by better understanding the road-crossing behaviour of species such as the koala.

Impacts and Potential Mitigation of Road Mortality for Hedgehogs in Europe

“…This is associated with individual responses to roads and biological characteristics, such as reproductive strategy and pre-hibernation foraging [ 68 ]. Individual-based movement patterns cause different exposure to traffic in the environment [ 41 ], which has important repercussions for reproductive output [ 10 ]. For example, for species such as hedgehogs that have a promiscuous mating system and maternal natal care, adult females have a more important role in population growth than males [ 69 ].…”

“…For example, for species such as hedgehogs that have a promiscuous mating system and maternal natal care, adult females have a more important role in population growth than males [ 69 ]. Moreover, the frequency distribution of age-at-death in a population is central to life history evolution and population dynamics [ 10 ].…”

“…The consequences of road mortality are typically two-fold: (1) direct depletion of individuals from a population and/or (2) fragmentation of populations and reduced gene flow [ 7 , 8 , 9 ]. Importantly, these consequences can alter meta-population structure and population fitness, in turn increasing the risk of local extinction [ 10 ]. Roads are therefore considered responsible for the nationwide decline of certain species and a limiting factor in the recovery of others [ 11 , 12 ].…”

Are wildlife escape ramps needed along Australian highways?

“…Koalas will frequently cross unfenced roads but will also readily use retrofitted underpasses (AMBS ; Dexter et al . , ).…”

“…Translocation of nine Koalas from the study area three years before our study may have left a small local population and precludes an evaluation of the necessity of escape ramps for this species. Koalas will frequently cross unfenced roads but will also readily use retrofitted underpasses (AMBS 2012;Dexter et al 2016Dexter et al , 2018. Escape ramps were devised in the USA to enable very large abundant migratory mammals to escape through the roadside wildlife exclusion fence if they gained entry where the fence ended, or through holes in the fence where the fence was damaged (Bissonette & Hammer 2000;Siemers et al 2015).…”