It began on the evening of Jan. 11, with the first sighting of a stranded whale on a beach off Tuticorin, a port city in the southern Indian state of Tamil Nadu.
In the hours since, at least 50 short-finned pilot whales have been found stranded on a stretch of beaches about 8-kilometers long, J K Patterson Edward, director of the Tuticorn-based Suganthi Devadason Marine Research Institute, told Quartz. Other news reports suggest that the number of stranded whales could be closer to 100.
“The whales started reaching the shore in groups around 5pm (Jan. 11). It is very strange. In 1973, when we were boys, we witnessed the same phenomenon,” Rajan, a fishermen, told the Times of India newspaper. “However, not these many washed ashore then.”
So far, at least 20 of them have died, The Times of India added, and the rest will become distressed and die unless they can be rescued quickly. Pilot whales are members of the dolphin family, with adult males measuring up to 20 feet and weighing up to 3 tons.
Exactly why whales beached themselves isn’t entirely clear. In an interview to the Scientific American magazine in 2009, here’s how Darlene Ketten, an expert on hearing in marine mammals at the Woods Hole Oceanographic Institution in the US, explained the phenomenon:
I often use the analogy of a car crash, because a lot of things can go wrong but you get the same result. Statistically, we are only able to determine the cause of a stranding in about 50 percent of all cases worldwide. In some cases it is obvious, like a ship strike leaving an animal in poor condition. In the northeastern United States, pneumonia is a common cause of stranding. We see other diseases and trauma, such as shark attack on whales or dolphins or attacks by members of the same species. Poisonous “red tides” will also affect marine mammals. Some strandings have been speculated to be related to anomalies in the magnetic field.
Military sonar has been implicated in the mass stranding of beaked whales. Although there have been environmental groups publishing press releases about all whales being affected by sonar—that’s never been demonstrated.
But this particular whale stranding in Tuticorin could be a result of human activity off the coast.
“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,” Siddharth Chakravarty of Sea Shepherd Global, a marine conservation organisation, 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.”