Along the coasts of Gulf of Kutch, Gulf of Mannar, Palk Bay and the Andaman and Nicobar Islands lives a slow-moving marine creature that loves sea grass – the dugong. Assessed as vulnerable by the IUCN Red List of threatened species, this ‘sea cow’ is also considered regionally endangered in India as only 200–300 individuals remain. This prompted the government to initiate the Endangered Species Recovery Programme in 2015 for their long-term conservation and persistence.

But studying dugongs is easier said than done. You cannot spot them using traditional methods such as boat surveys and due to their small population size, their sightings are very rare. Australian researchers had previously employed aerial surveys to study the distribution, population and habitats of dugongs.

Since 2019, India also adopted light-weight unmanned aerial vehicles for studying marine megafauna specifically dugongs. The surveys, led by Sagar Rajpurkar from Wildlife Institute of India, Dehradun, were carried out along with others in Andaman and Nicobar Islands within the Marine Protected Areas of Mahatma Gandhi Marine National Park and Rani Jhansi Marine National Park, and adjoining areas. The paper detailing the survey was published recently in Current Science.

The researchers note that unmanned aerial surveys can help cover large spatial scales, reduce survey effort and time, and are cost-effective. “The lightweight drones we used were less noisy and did not disturb the marine mammals. It was flown at a height of about 200-300 meters to first scan an area for dugongs and then brought down to 80-100 meters to closely follow the species. Since the video resolution is high from even this height, it can be used in the future to identify individuals, track movements and monitor behaviour of individuals,” explains Dr Anant Pande, one of the authors from the Wildlife Institute of India, Dehradun.

“The Ministry of Civil Aviation had recently announced that no prior permission or approvals are needed for drones used for research. This can pave the way for new research in remote areas,” he adds.

Though the drone is capable of flying into the sea up to 10 km, the team used it for about 2.5 to 3 km. Dr Pande adds that since dugongs live near the coast, it was easy to study them from land and offshore surveys if needed, for example, for dolphins or whales, can be done by flying the drone from a small boat with a platform.

During the survey, the team recorded mother and calf pairs of dugongs, sea turtles, spotted eagle ray, zebra shark, stingrays, needlefish, squids, and several fish shoals.

“Unmanned aerial vehicles surveys should be adopted as a tool by State Forest Departments to monitor marine fauna of conservation concern and for tackling illegal activities in the Marine Protected Areas,” concludes the paper.

Dr K. Sivakumar, Scientist and Project Coordinator of the Dugong Recovery Program at Wildlife Institute of India adds that future plans include drone surveys to map seagrass habitats, monitor marine megafauna, and conduct a spatial assessment of Marine Protected Areas.

Source: 27 July, 2021, The Indian Express