Drones with thermal cameras are revealing the secrets of elusive Australian forest wildlife

The sound of a large drone humming over a forest at night, combined with a bright floodlight, is an eerie sight. It might evoke ominous thoughts of a search-and-rescue operation.

But our new study published in Ecological Applications shows that drones equipped with thermal cameras could also help detect and monitor some of Australia’s most elusive forest wildlife. In turn, they can help us make smarter, evidence-based decisions for conservation.

Elusive creatures few have seen

Eucalypt forests across Victoria shelter some of our most threatened nocturnal wildlife, such as Victoria’s critically endangered faunal emblem, Leadbeater’s possum, and the endangered southern greater glider. Few people would have seen these creatures in the wild – in large part because they spend most of their time high in the trees and can be incredibly difficult to detect.

But monitoring them is crucial. Populations are shrinking due to habitat loss, forest fires and climate change. Conservation and management decisions depend on accurate data about where these animals live and how abundant they are.

Traditionally, researchers conduct these surveys by walking along defined paths called transects through the forest, sweeping torches to catch the eyeshine of animals as it reflects back to the observer. Eyeshine varies by species – greater gliders glow golden, Krefft’s gliders blue, and brushtail possums red. But binoculars help in identifying species as well.

But this process – known as “spotlighting” – can be slow, labour intensive and potentially dangerous for the survey teams, especially in steep or dense forests. Even with careful sampling, spotlighting often fails to detect all the animals present.

Remote sensing techniques that help collect information from a distance are changing the game for wildlife monitoring. For example, acoustic recorders can survey birds and frogs and motion-activated cameras can detect shy mammals. This recently led to the discovery of critically endangered Leadbeater’s possums far outside their assumed range.

But animals like the greater glider rarely make calls that can be captured by acoustic recorders and their strict diet of eucalypt leaves means they can’t be attracted to baited camera traps.

This is where drones equipped with thermal cameras come in.

Scanning the canopy – from above

Until recently, most thermal drone surveys had been tested on animals in open landscapes, such as feral goats, or in tree plantations, such as koalas. They have also helped find some elusive species in the rainforests of Queensland that are active during the day. But no one has previously studied their effectiveness in detecting nocturnal animals in native forests.

As part of our new research, we flew drones across forest compartments up to 200 hectares in size while also conducting ground-based surveys to compare results. Drones flew systematic paths over the canopy, using thermal cameras to detect animals’ heat signatures. After an animal was spotted, a zoom camera and floodlight were then used to identify species.

The results were striking. Our drones detected all nine tree-dwelling mammals expected in the study areas. Species commonly surveyed using spotlighting were recorded most frequently. But we also recorded species that are usually detected using remote cameras, such as Leadbeater’s possums, or through their calls, such as yellow-bellied gliders.

In total, we made more than 1,000 observations of native mammals, as well as forest birds, and ground-dwelling fauna such as bandicoots, wombats, feral deer and cats.

Drone surveys were also far more efficient – one drone survey could cover roughly ten times the area a spotlighting team could survey in the same time.