By Shreya Dasgupta
Legend has it that lonely sailors mistook them for beautiful, mythical mermaids. But as it turns out, the muse behind these beguiling sea nymphs was instead the dugong – a rather ungainly, gentle and mini-bus sized marine mammal, cousin to the manatees and part of the sea cow family. However, while they may have once fuelled stories for fairytales and Disney movies, their far-from-glamorous life is currently under serious threat in many parts of the world.
One such threatened population dwells in the Andaman and Nicobar Archipelago, a group of islands in the Indian Ocean. The dugong (Dugong dugon) distribution here has plummeted by more than fifty percent over the last 50 years, according to a recent study published in PlosOne. In the sites where dugongs persist, the researchers found that they show location fidelity, seeking out the same areas they did 50 years ago instead of populating new ones.
Researchers Elrika D'Souza and Vardhan Patankar began studying dugongs in 2007, their first encounter with one of these gentle giants lasting over a five-hour swim. Currently at the Nature Conservation Foundation at Bangalore, India, D'Souza and Patankar continued to observe the behavior of the few dugongs of the archipelago they could individually spot and identify. But as reports of dugongs in the area declined, they decided to broaden their study to include the local distribution of dugongs in the past as well as the present.
To achieve this, D'Souza and her team collected two kinds of data – historical data that would give them a glimpse into the dugong's past distribution, and current data that would tell them how they fare now.
For the former, they looked through newspaper clippings, fishery bycatch records, forest department records and prior publications, as well as interviewed wildlife experts working in the islands to determine where dugongs had been seen in the past. They collated a total of 55 records of 124 individual dugongs extending over the last 50 years (1959-2009).
The team then used this data on dugong presence and absence in the different seagrass meadow locations, to predict where dugongs might have occurred in the past across the islands.
"This is one of the few studies that have actively used the historical data itself to predict past occupancy of an animal," said Nachiket Kelkar, a researcher at NCF and co-author of the study. More....