Predicting cassowary–vehicle collision in the Wet Tropics of Australia

Bruce L. Webber; Matt Bradford; Noboru Ota; David Westcott

doi:10.1071/WR23089

RESEARCH ARTICLE (Open Access)

Previous Contents Vol 52(4)

Predicting cassowary–vehicle collision in the Wet Tropics of Australia

Bruce L. Webber

^A ^B ^* , Matt Bradford ^C ^D , Noboru Ota ^A and David Westcott ^C

+ Author Affiliations

- Author Affiliations

^A CSIRO Health and Biosecurity, Floreat, WA 6014, Australia.

^B School of Biological Sciences, University of Western Australia, Crawley, WA 6009, Australia.

^C CSIRO Environment, Atherton, Qld 4883, Australia.

^D Present address: Billycart Brewing, PO Box 516, Atherton, Qld 4883, Australia.

^* Correspondence to: bruce.webber@csiro.au

Handling Editor: Aaron Wirsing

Wildlife Research 52, WR23089 https://doi.org/10.1071/WR23089

Submitted: 19 July 2023 Accepted: 18 March 2025 Published: 11 April 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

Roads act as significant disruptors to wildlife movement through landscapes, even in relatively undisturbed areas. Large terrestrial vertebrates often choose to cross roads, which brings risk of injury or mortality from vehicle collision. In the Wet Tropics bioregion in Queensland, Australia, the range of the southern cassowary (Casuarius casuarius) spans a diversity of habitats and intensity of road network development. There has been a large increase in the human population within cassowary habitat in recent decades and at local scales there remains concern over increasing mortality caused by vehicle collision.

Aims

To inform management decisions on where is the best to direct collision mitigation resources based on identifying environmental factors that correlate with higher collision risk.

Methods

We collated 28 years of data on cassowary–vehicle collisions from across the bioregion and sought to identify ecological, physical and anthropogenic correlates of collision at both landscape- and location-specific scales.

Key results

We identified a major hotspot of reported cassowary–vehicle collisions in a large area of coastal lowland between Innisfail and Mission Beach. At a landscape scale, vehicle collisions increased significantly when the proportion of cassowary core habitat in the landscape was >50% and as the density of major roads increased. To a lesser extent, collisions increased when minor road density exceeded 400 m/km². At a location-specific scale, vehicle collisions are more likely to occur on straight sections of major roads that have high canopy cover on both sides of the road and were less likely to occur on roads passing through land use types with low canopy cover.

Conclusions

Our findings highlight the significant challenges faced in effectively addressing the cassowary–vehicle collision problem in the Wet Tropics bioregion. Where cassowary habitat and roads intersect, cassowary mortality will occur.

Implications

Construction of new roads within rainforest should be avoided where possible and over- or under-passes should be constructed on new and existing major roads that intersect cassowary habitat and where location-specific correlates of cassowary collision exist. In addition, further collision mitigation measures such as traffic slowing should be targeted with these results in mind.

Keywords: cassowary, habitat fragmentation, mortality, road density, road risk, threat mitigation, vehicle speed, visibility, wildlife-vehicle collision.

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