In the recent past, drones have become an effective tool in wildlife conservation. From safeguarding anti-poaching efforts to reducing man-animal conflicts, their constant aerial presence and surveillance have come handy in the wild.
Now, researchers and scientists from Western Sydney University and the Taronga Conservation Society in Australia are detecting and counting flying-foxes in tree canopies using a new method: thermal camera-equipped drones. This innovative new method, which was described earlier this week in the journal Remote Sensing in Ecology and Conservation, is contributing to efforts to count the grey-headed flying-foxes (Pteropus poliocephalus), a species classified vulnerable to extinction due to population decline. A species of the flying fox is also found in the Indian subcontinent, the Indian flying fox or Pteropus medius.
According to an official news release, the new method is shown to be accurate and precise, by comparing ground counts of flying-foxes in single trees to counts obtained from the drone, from repeated drone surveys, and from multiple human counters.
The method also uses advanced image detection techniques, including machine-learning and computer vision to semi-automate flying-fox counts from the drone-acquired imagery. “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 Eliane McCarthy, lead author and master of research graduate Eliane McCarthy at the Hawkesbury Institute for the Environment.
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McCarthy explains that at present there are two main methods for getting accurate counts of a flying-fox colony. One, during the day, when the flying-foxes are roosting and therefore quite static, or, two, during the evening when they leave the roost to forage on nectar and fruit and can be counted as they depart the roost. “However, there are several issues in conducting ground surveys: the terrain can be difficult and physically-challenging for counting personnel and their presence can disturb rooting 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”, co-author John Martin, a research scientist at Taronga, explains in the release.
The covid-19 pandemic has not made things any easier. Globally, scientists and wildlife conservationists have had to devise new methods to continue their research as it is still not safe to step out in some parts of the world.
However, Australia is not the only location where drones have come in handy for wildlife-related research. At the Ostional National Wildlife Refuge on Costa Rica’s Pacific coast, hundreds of thousands of sea turtles come ashore to lay their eggs during mass-nesting, making it one of the most important nesting beaches on the planet. Drones have given scientists better insights into just how important the beach and its nearshore waters are for the species.
For instance, in August 2015, using a fixed-wing drone to conduct aerial surveys of olive ridley sea turtles in waters off Ostional during four days, scientists from Duke University and the University of North Carolina at Chapel Hill (UNC-CH) had estimated that turtle densities there may reach as high as 2,086 animals per square kilometer during peak nesting season.
The researchers had published their peer-reviewed paper in the Scientific Reports journal in December 2018. It was the first study that used unmanned aerial systems (UAS), or drones, to estimate the abundance of sea turtle populations.
Olive ridleys are classified as vulnerable on the IUCN Red List of Threatened Species, the world’s most comprehensive inventory of the global conservation status of biological species. In India, lakhs of olive ridleys arrive for mass nesting along the Odisha coast every year.
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