Local authorities and fishermen in the southern Indian state of Tamil Nadu are racing against the clock to save as many as 81 short-finned pilot whales found stranded on a 16-kilometre stretch of beach yesterday.

Despite their efforts to drag the beached whales back into the ocean, at least 45 of the marine mammals are now feared dead. 

"The whales started reaching the shore in groups around 5pm (Jan. 11)," a local fishermen told Times of India. "It is very strange. In 1973, when we were boys, we witnessed the same phenomenon."

Pilot whales are known for their unusual beaching behaviour, which scientists don't yet fully understand. The 1973 stranding event claimed the lives of 147 short-finned pilot whales, leaving experts puzzled.

Although short-finned pilot whales are part of the oceanic dolphin family, Delphinidae, their behaviour more closely resembles that of larger whales. Adult males measure in at about 18 feet (5.5 metres) and can weigh up to three tonnes.

As was the case 43 years ago, experts are not entirely sure what caused this week's tragic stranding. Whale beaching has been linked to everything from ship strikes and disease to shark attacks and toxic "red tides". According to Siddharth Chakravarty of marine conservation organisation Sea Shepherd Global, human activity may also be to blame.

“The increase in sound levels from ship traffic, sonic testing and oil drilling interferes with the navigation of the whales, which often results in the sort of mass stranding we are seeing in Tamil Nadu,” he told Quartz. “Whales are also very social and often entire pods will follow individual whales closer to shore, which can result in the entire pod stranding itself.”

We'll keep you updated on this story as more information becomes available.

Header image: Ron Knight