Research with DEEP

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Animal-vehicle collisions on Tasmanian roads

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The aim of this research was to determine the factors associated with a high risk of wildlife-vehicle collisions in Tasmania, focusing on large-bodied, frequently encountered marsupial species. Given the findings of past research, roads with a speed limit ≥ 80 km/h that had a history of recorded roadkill were chosen. Three crepuscular/nocturnal species were selected as targets: two macropods—the Tasmanian pademelon (Thylogale billardierii), and Bennett’s wallaby (Macropus rufogriseus rufogriseus)—and the quadrupedal bare-nosed wombat (Vombatus ursinus). Although the wombat did not rank highly on the list of roadkill victims in past surveys, most likely due to lower abundance compared to macropods, it is suffering a population decline that makes it more vulnerable to threats. For this species, there is a risk that mortality from vehicle collisions might exert a substantial demographic pressure in the near future, warranting further attention. Other potential target species―including native predators and small marsupials―were not studied because of sample size and detection error issues.

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My specific goal was to test the consistency of habitat suitability, land-use (habitat) type, and road-visibility conditions in predicting road mortality in Tasmania, with habitat suitability estimated using climatic-niche modelling. For this study, relatively well-trafficked peri-urban or rural roads with high speed limits were chosen. The objective was to quantify bias-corrected numbers of the three target species killed by vehicles on Tasmanian roads, using a standardised, replicated survey design, and to detect any spatial, sex or seasonal patterns. The applied aim of the research was to determine roadside factors that might be effectively mitigated to reduce future roadkill rates, and to identify ‘hotspots’ where management interventions might be most effective.

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