Population of dugongs estimated at 270 in Tamil Nadu

The estimated population of dugongs in Tamil Nadu has been put at 270. A survey undertaken by the Wildlife Institute of India (WII) in collaboration with the Forest Department along the Tamil Nadu coast, has found that there are 158 dugongs in Palk Bay and 112 dugongs in Gulf of Mannar.

“The findings indicate that the dugong population in Tamil Nadu is stable and doing well, says Supriya Sahu, additional chief secretary, Environment, Climate Change and Forests Department.

In a social media post, she said together, Palk Bay and Gulf of Mannar now represent the largest viable dugong population in India. This is largely attributed to the implementation of the Dugong Recovery Programme by WII, supported through CAMPA, along with the proactive and sustained conservation efforts of the Forest Department, including community engagement to protect dugongs, she said.

Importantly, the confirmed presence of mother calf pairs provides evidence of active breeding. The report also highlights the notification of the Dugong Conservation Reserve in Palk Bay, covering 448 sq.km of its core habitat by the government, as a significant milestone towards long-term protection of the species, she said.

The UAV survey was carried out in line with standardised protocols and methodology. “The survey has established a benchmark and will be scaled up in future for regular monitoring of the dugong population,” said Dr. J. A. Johnson, Scientist-F, WII, who led the assessment team.

The present study is the first systematic, UAV-based population estimate. The application of standardized fixed-width strip transacts, syncrhonised drone deployments, and availability-bias correction produced reliable density and abundance estimates comparable with international best practices.

The earlier estimated dugong population in Palk Bay and Gulf of Mannar region was about 175 individuals, an estimate done based on the interview-based survey conducted in 2012 and 2013. The present numbers based on aerial survey detection indicates that the dugong population was doing well and these two areas remain the stronghold of dugong population in the country, the report said.

Surveys were conducted across 48 locations using 96 aerial transects covering 37.44 sq.km with a total flight effort of 288 km. A total of nine dugongs were sighted on effort. These observations yielded an overall abundance estimate of 270 (plus or minus 16) dugongs for Tamil Nadu.

While the study represented a significant advancement in dugong population assessment, it also had some methodological limitations. The present UAV-based surveys were restricted to a fixed transect length of approximately 3 km, determined by drone endurance, battery life and operational safety requirements in coastal conditions. The estimates may not fully account for individuals that temporarily move into deeper waters, the report added.