Mumbai: While climate change is real and rising levels of manmade pollution continues to pose serious threats to marine life, the beaching of dead dolphins and whales every fortnight on the city's seacoast might have the moon and its pull on the tides to blame for disorientating marine mammals and driving them to their deaths.
A year-long study by Myvets Charitable Trust & Research Centre, to assess pathological, seasonal and anthropogenic causes, reveal that most of the strandings occurred during the new moon and full moon phase and during receding tides in the region.
The finding of a humpback dolphin along the Worliseaface on Friday morning, too, was an occurrence three days ahead of a full moon. A total of 13 deaths have been reported in the past one year. There have been up to 70 unreported deaths of marine mammals washed out in remote shores and deep mangroves, says YuvrajKaginkar, wildlife conservationist, Myvets.
What seems like a spate of whale and dolphin strandings on Maharashtra's coastline in a year is in fact not a new phenomenon. "It's been happening for decades. It's just that there are more observers present now to report; people are generally alert to these sightings thanks to phone cameras and social networks and young scientists are taking reasonable interest in it," explained Chennai-based Kumaran Sathasivam, author of The Marine Mammals of India and who runs a database of marine mammal strandings.
"Forensic investigations indicated that the animals were healthy when stranded," said Madhurita Gupta, wildlife conservationist and president of Myvets. "After opening the carcass of most dolphins, no plastic or foreign body was found inside the stomach; nor were there any parasitic infestations inside the intestines. Teeth showed no signs of aging. Only the two whales washed ashore at the Gorai and Juhu beaches had injuries on the tail fin. The others had no cuts or wounds on the body," the report states.
Instead, the findings pointed to an error in navigation within the social group of the mammals. Further study confirmed a correlation between marine mortality and the lunar cycle— fluctuations in the ocean bed, unusual currents and increased tidal bulges—preventing whales and dolphins from geo-navigating effectively. Quakes around those dates causing seismic shifts on the seabed seem to have addled their navigation further, the researchers said.
"Gravitational changes due to the lunar effect alter their migration patterns and disorient them," Gupta explained. Subsequently, some of them lose track of the rest of the pod, stray into shallow waters and die after a struggle in the trap of a receding tide.
Other causes responsible for the strandings can be outbreak of morbillivirus common in marine mammals, factory waste and sewage disposed into the sea and oil spills.
