MADURAI: A school of shortfinned pilot whales beached on Tiruchendur coast in southern Tamil Nadu on Monday night and Tuesday morning, setting off a massive rescue effort by officials and fishermen over a 16km stretch of sand.Of the 81 whales washed ashore, 45 were dead by afternoon despite efforts to save them. Weighing from 1,000 to 1,500kgs 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.It was on Monday after noon that fishermen first noticed an entire pod of whales swimming close to shore. By night, nearly 40 of them had washed ashore. The fishermen kept a vigil the entire night, making constant at tempts to push them back into the water. Local district officials and the Coast Guard were informed about the incident and helped in rescue work. Experts said the whales may have got disoriented while foraging near the shore at a time when the sea water had turned cool and salinity was down. The Alanthalai and Manapad stretches of the Tuticorin coastline, where the whales were stranded, have a rocky seabed. The whales may have swum close to the shore during high tide and then suffered injuries as the tide went down.“These are social animals which follow the lead fish that uses sonar navigation. The lead ones could have lost way for some reason, and this may have resulted in the beaching,“ said G Sugumar, dean of Fisheries College and Research Institute, Tuticorin.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. 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. Ravikumar said work to save the whales commenced on Monday night.“Rescue effort started with the help of fishermen, the fisheries officials and the team from the fisheries college. But the whales were too heavy . Many of them which were pushed into the sea on Monday night were washed ashore elsewhere on Tuesday morning. But we have managed to send 36 back into the sea and we pray that they swim away ,“ he said.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 rea son for the beaching.