• Tony Bosworth

Hawkesbury Institute counting flying foxes with thermal drones

Scientists from the Hawkesbury Institute for the Environment at Western Sydney University's Richmond campus - have developed a new way of counting endangered flying foxes - using thermally equipped drones.

Flying foxes are a globally threatened species, so the new method of counting them helps build information about colonies, and also means less disturbance for the bats.

This innovative new method, published in the journal Remote Sensing in Ecology and Conservation, helps count grey-headed flying-foxes (Pteropus poliocephalus), a species listed as vulnerable to extinction due to population decline.

detecting and counting flying-foxes in tree canopies by using thermal camera-equipped drones.

“We can now use drones to obtain accurate and precise measures of colony abundance semi-automatically, thus greatly reducing the amount of human effort involved for obtaining abundance estimates,” said lead author and Master of Research graduate, Eliane McCarthy, at the Hawkesbury Institute for the Environment.

Thermal drone imagining (right) shows roosting bats, making them easier to count

“At present there are two main methods for getting accurate counts of a flying-fox colony: during the day, when the flying-foxes are roosting and therefore quite static, or during the evening when they leave the roost to forage on nectar and fruit and can be counted as they depart the roost,” said Ms McCarthy.

The new method is shown to be accurate and precise, by comparing ground counts of flying-foxes in single trees to counts from the drone, from repeated drone surveys, and from multiple human counters.

The work also uses advanced image detection techniques including machine-learning and computer vision methods to semi-automate flying-fox counts from the drone-acquired imagery.

“There are several issues in conducting ground surveys," says co-author Dr John Martin, a research scientist at Taronga Zoo.

"The terrain can be difficult and physically-challenging for counting personnel and their presence can disturb roosting flying-foxes, reducing the accuracy of the estimate. Fly-out counts rely on rapidly counting fast-moving animals at dusk, when the light is fading, complicating these assessments,” he said .

“We demonstrated that drone-acquired thermal imagery can be used to accurately and precisely quantify the abundance of flying-foxes in a roost, and that semi-automated methods for counting flying-foxes in thermal imagery are comparable to human assessments in their accuracy”, said co-author, Associate Professor Boer.

“This method is very valuable for reliably monitoring the abundance of individuals in flying-fox roosts and will aid in the conservation and management of this globally threatened group of flying-mammals, as well as other warm-blooded tree-roosting species,” said senior author, Associate Professor Justin Welbergen.

Main pic - thanks to Harry Cunningham

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