Tamil Nadu: In an unusual phenomenon, a school of short-finned pilot whales beached on Tiruchendur coast in southern Tamil Nadu on Tuesday. Of the 81 whales washed ashore, 45 were dead by afternoon despite efforts to save them. Of these, 37 were adults and eight were sub-adults.

Pilot whales – known to be among some of the most social aquatic mammals — are so named because they are led or ‘piloted’ by a leader in their search for food or breeding grounds.

At least 45 whales died after they washed ashore overnight on a beach in Tamil Nadu’s Tuticorin district, officials said on Tuesday, with experts attributing the deaths to a possible underwater disturbance like an earthquake or volcano.

While beaching of whales and other aquatic animals is common around the world, experts said it was rare to find such a large number of whales washing up ashore and hinted at the mammals being disoriented by underground activity.

Collector M Ravikumar rushed to the spot on Tuesday morning to oversee the rescue and wildlife officials from the Gulf of Mannar Marine National Park were also called in to investigate the incident.

Marine scientists working in the Gulf of Mannar Biosphere Reserve say that the short-finned pilot whales are deep water whales, diving up to 1,000 metres, who form stable matrilineal kinship groups. This particular group could have stranded while in search of food, the favourite being squids.

By Tuesday evening, 45 of the whales that had perished were buried along the shore after an autopsy. “We feel that it was behavioural change. They ran into shallow waters and could not get back into deep sea,” said Deepak Bilgi, wildlife war den, Gulf of Mannar Marine National Park. He ruled out changes in marine ecology as the reason for the beaching.

Weighing from 1,000 to 1,500 kgs and about 4metres in length, these enormous sea mammals struggled for life as rescuers made valiant attempts to push them back into the water. Eventually, 36 of them were guided back into the sea though it was not clear how many of them survived.

Mascarenhas, a local resident who happened to be on the spot on Monday evening, said if fishermen had not helped in rescue efforts, more whales would have been dead.