Frequency and causes of kangaroo–vehicle collisions on an Australian outback highway
Ulrike Klöcker A , David B. Croft B C D and Daniel Ramp BA Museum Alexander Koenig, Rheinische Friedrich Wilhelms Universität Bonn, 53113 Bonn, Germany.
B School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
C University of New South Wales Arid Zone Research Station, Fowlers Gap, via Broken Hill, NSW 2880, Australia.
D Corresponding author. Email: d.croft@unsw.edu.au
Wildlife Research 33(1) 5-15 https://doi.org/10.1071/WR04066
Submitted: 12 August 2004 Accepted: 25 November 2005 Published: 7 March 2006
Abstract
Kangaroo–vehicle collisions are frequent on Australian highways. Despite high economic costs, detrimental effects on animal welfare, and potential impacts on population viability, little research has been done to investigate the impact of road mortality on kangaroo populations, where and why accidents occur, and how the collisions can be mitigated. We therefore collected data on species (Macropus rufus, M. giganteus, M. fuliginosus, M. robustus), sex and age of kangaroos killed on a 21.2-km bitumenised section of outback highway over 6 months in far western New South Wales, Australia. The spatial and temporal distribution of road-killed kangaroos was investigated in relation to the cover and quality of road-side vegetation, road characteristics, the density of kangaroos along the road, climatic variables and traffic volume. A total of 125 kangaroos were found killed on the road at a rate of 0.03 deaths km–1 day–1. Grey kangaroos of two species (M. giganteus, M. fuliginosus) were under-represented in the road-kill sample in comparison with their proportion in the source population estimated during the day. No bias towards either sex was found. The age structure of road-killed kangaroos was similar to age structures typical of source kangaroo populations. Road-kills mainly occurred in open plains country. In road sections with curves or stock races, road-kill frequencies were higher than expected. Greater cover and greenness of roadside vegetation at the verge probably attracted kangaroos to the road and variation in this vegetation affected the spatial distribution of road-kills. The temporal distribution of road-kills was positively correlated with the volume of night-time traffic. The probability of a kangaroo–vehicle collision increased exponentially with traffic volume. Results are discussed in relation to the potential for mitigation of kangaroo–vehicle collisions.
Acknowledgments
This study was funded by the NSW Road and Traffic Authority, the NSW Wildlife Information and Rescue Service and the International Fund for Animal Welfare. We thank the staff at Fowlers Gap (Paul Adams, Will Evans and Keith Troeth), Ingrid Witte and Rebecca Montague-Drake for assistance with the study.
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