Recurring incidents of stranding and death of whales along the various coastlines of the country have baffled marine biologists and experts. losing their way from their deep sea migratory paths due to natural or manmade ocean disturbances is believed to be among the probable causes of their beaching.
However, not much scientific study has so far been done to assess the behaviour, habitat and adaptability of these giant marine mammals.
The latest of these incidents took place in Odisha on Friday. The body of a 66-feet-long whale was washed ashore near the mouth of Chinchiri river off the coast of Bay of Bengal. This was preceded by a similar incident in the State when carcass of a 33-feet long whale was found off the Ganjam coast.
The Arabian Sea coast of Maharashtra also witnessed two successive incidents of whale stranding recently. While a 40-feet-long blue whale was found in shallow waters along the Dapoli coast in the Konkan region, a 37-feet-long Bryde’s whale was found dead on Juhu beach. The former was, however, rescued and sent back to the sea.
The most puzzling of them all was the mass stranding of nearly 80-100 baleen whales along Tuticorin coast of Tamil Nadu between January 12 and 13. While about 45 of them died, the remaining were pushed back to the sea by experts and authorities.
Throwing light on the above phenomenon, Dr Abhijit Mitra, Faculty Member, Department of Marine Science, University of Calcutta pointed out that an earthquake with a magnitude of 6.5 and 6.9 on the Richter scale had occurred
in the Philippines and Indonesia, respectively on January 11.
“The vibration of seabed and overlying water could have posed an adverse impact on the sensory system of whales that probably disoriented their direction of migration. Nearly 75 whales were found beached near Mandapu village in Tuticorin district in Tamil Nadu shortly after the incident,” said Dr Mitra.
The whales are social animals, moving in groups. They have poor visibility and communicate with each other through echolocation or
sound made by them to stay in touch with each other during migration.
“However, due to disturbances in the sea water created by the movement of warships, thundering, cyclone etc., echolocation of certain individual whale may get disrupted, turning it haywire. In the process, such individuals tend to get washed ashore as seen in Odisha and Maharashtra,” said Dr K Sivakumar, Marine biologist, Wildlife Institute of India (WII).
Other factors — including climate change, tectonic movements of sea beds caused by sub oceanic volcanoes or earthquakes — also impact the overlying ocean water, which in turn can influence the whales as well.
Further, disturbances in the form of Active SONAR (sound navigation and ranging) may also affect certain species of whales. SONAR emits varying frequencies of sound vibrations under water and used to detect marine vehicles. The immense pressure of such waves may cause internal bleeding in the ear and brain tissues, killing or disorienting whales, including infants from their mothers.
It is, however, rare for such individual stranded whales to survive, said Dr Mitra. “The habitat of the whales is in deep sea. The shallow water on the sea coast puts them under physiological stress, which they are seldom able to withstand,” he explained.
Illness may also lead to separation of whales from its group, he said, adding natural deaths also result in floating their bodies ashore.
The Environment Ministry with the WII is to initiate capacity building measures for the rescue of stranded whales and other marine species under the Sea cow & Dugong Recovery programme, said Dr Sivakumar. However, more research and studies need to be conducted on the species.
There are about 80 species of whales found in the oceans across the world. Blue whales and Sperm whales are among the ten most endangered species of this giant mammal.
