Episodes of mass stranding of whales across the world show pilot whales to be the most commonly involved in the phenomenon.
More than one hypothesis on stranding of whales, including short-finned pilot whales that died in large numbers on the Thoothukudi coast in Tamil Nadu, point to hearing sensitivity of these toothed mammals implicated in such events.
It is possible, for instance, that a combination of environmental factors such as high levels of man-made noise from shipping activity, the resulting hearing loss and new stresses might be affecting their behaviour.
This factor has been incorporated into rehabilitation efforts as a result.
Sensitivity to low frequency sound is key for whales, as they use echolocation for orientation.
Injury caused to one pilot whale could have implications for an entire pod, as these squid-eating creatures generally found in deeper tropical and sub-tropical waters across the world act in a gregarious manner and could fatally follow a sick individual to the shore as a group.
In a recent episode of mass stranding of 40 short-finned pilot whales recorded in Elizabeth Bay, North Andaman, in 2012, a research team of the Zoological Survey of India and the Ministry of Environment and Forests proposed several possible explanations - including an undersea earthquake of 4.7 Richter magnitude that could have sent out magnetic waves and disoriented them, causing them to change their navigational path.
Other possible causes for the episode reported by the research team in Current Science three years ago are disorientation caused by unfamiliar territory that greeted the whales as they followed fast-moving dolphins, tidal currents, or powerful military sonar from ships off the Andamans that could have resulted in the stranding.
What is emphasised by researchers is the need for closer scientific study of the 40 whale, dolphin and porpoise species found in the Indian Ocean in general and 25 species that occur in Indian territorial waters in particular.
Before the Thoothukudi episode, major short-finned pilot whale stranding episodes reported in the sub-continent involved several dozens in Kolkata (1852), a big school of 147 in Tamil Nadu (1973), and the 40 in the Andamans.
This protected species is also affected by intensive fishery methods such as trawling, gillnetting and use of long lines, leading to regulations on their use in North America.
