Understanding koala movements and road mortality in urban areas

Vehicle collisions can be a major threat to koalas in residential areas.

In collaboration with the Gold Coast City Council, a drone company, and the Queensland State Government, we assessed the population, distribution, and vehicle collision risk of koalas in the Burleigh Green Space Conservation Reserves, an area of the Gold Coast with one of the most conspicuous urban koala populations.

We used drones equipped with high-resolution cameras flown above the canopy to estimate population density and abundance, based on 2 methods that account for detectability, and to map koala distribution over 2 years. We also assessed the effectiveness of different survey methods.

We found that koalas regularly cross roads to move in and out of the urban bushland fragments, so the population fluctuated. The Burleigh Heads area supports an exceptionally high density of urban koalas: 0.49–0.93 koalas/ha, a population of 52–100 individuals in the 108 ha of reserves.

Koalas were more likely to be found in parks and gardens with high human use than in natural vegetation (much of which was rainforest), and they did not avoid road edges. Fencing did not alter koala distribution or the location of collisions (although fencing in this area was not a koala-specific design).

Based on 72 collision records from 2008 to 2025, busier roads were associated with more fatal collisions. There were 7 times more collisions with koalas on highways than on local roads. We identified areas of the highest koala densities and particular roads that were collision hotspots, and recommended potential sites for targeted mitigation measures, such as wildlife crossing structures and wildlife fencing at the highest risk locations to reduce koala mortality.

Researcher