The cetaceans are one of only four species of dolphins in the world that inhabit rivers and lakes, and number only around 2,000 in India, according to the conservation group. They are increasingly threatened by pollution, hunting and dam construction projects.
But researchers from the University of Tokyo have developed an underwater acoustic device that measures the individual sonar pulses or the clicking sounds emitted by the dolphins, which are as unique as fingerprints, said the WWF.
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photo by Mark N