On January 12 last as many as 75 whales were found dead in Tuthukudi district in Tamil Nadu out of the 100 short finned pilot whales which got disoriented and reached the shore.
These whales usually live in deep water and migrate from one place to other for search of food or for change of habitats. Again such schools of marine animals specially the mammals change their abodes from polar region to tropical region like birds to avoid severe cold and food. Commonly most species of whales periodically migrate from sub-polar regions to tropical regions and tropical latitudes to sub-polar latitude for change of seasonal-abode.
Generally, the marine mammals of cetacean group like whales, dolphins, porpoises, sirenia, sea-cows, sea lions and walruses belong to main groups of mammals found in marine complexity. But the Pinnipedia such as seals, sea lions, walruses are not found in the Indian seas as viewed by the great naturalist HS Prater.
Short finned pilot whales are oceanic animals, living only in the deep sea at a minimum depth of 300 mt. Such deep areas can be located around 50 nautical miles offshore in the Bay of Bengal.
Almost all the animals of the universe do not tolerate the interference of any one within their environment. At present the whole oceanic body of the world is highly polluted by man alone for various reasons. When the habitat of any animal or plant is polluted or disturbed for any reason, the situation compels the animal to migrate to safer places. The mammals are more sensitive to pollutions and generally migratory in nature. Sometimes the natural disasters like earthquakes within the underwater disorient them. Changes in magnetic field of earth create disorientations of various animals with in the oceanic floor. The animals can foresee the eventualities better. Noise and light pollutions are most detrimental for the sea mammals.
There is not much of research on marine animals and the cases of disorientation of animal population like land animals. The navigators and the oceanic fishermen always supply the information about the disorientation of schools of sea mammals and fishes. We have very little study on oceanic ecological systems. This is the first time we came across the mass scale causalities of pilot whales.
The whales give birth to their youngs generally in winter. The period of gestation varies from about six month to one year and case of larger whales varies from six months to one year. The fresh born whales are generally larger in size. Their rate of growth is also very fast. The whales become sexually adult when they attain 4 to 5 years age. As per the HS Prater, the whales grow very fast to attain the adulthood to counter balance the force of gravitation with the support of water. A female blue whale attains a length of 113 feet equal to 34 meters.
Most whale species travel in groups as a survival strategy, with dominant whales leading the pod. If the dominant whale becomes sick or confused, it may lead the pod too close to shore and get trapped by a low tide.
Sperm whales are one of the biggest and powerful aquatic mammals and can dive up to 2,000 metres and can hold breath for two hours, but their migration pattern and their home range in Indian Ocean is a subject that has to be explored in detail.
In Odisha once the dungong was found in Chilika lagoon, but at present such species is not located in the lagoon due constant threats to their existence for all type of pollutions. The dungong does not exceed 3.5 meter or 12 ft in length, whose body weight goes up to 150 kg or even more. At the present, the marine ecological systems are not congenial for oceanic mammals. The varied ecological systems of the oceanic origins are constantly polluted and poisoned in various ways due to uninterrupted competitions among nations. So the migration of sea creatures is inevitable. The oceanic mammals are the natural economic resources of man.
There are several international conventions and laws for restricting on fishing of whales in the oceans and seas as the populations of such mammals are depleting very fast. The mechanized finishing and voyages within the oceanic body are most detrimental for the populations of several marine populations. The biodiversities and the ecological complexes of marine origin are now dwindling for injudicious actions of man.
The writer came across an incident in Telkoi forests of Keonjhar district during 1966/67. It was a winter month, when parrots with other residential birds of the areas were found dying. The reasons could not be known as wild life wing of the State was not proficient to deal with the matter. Right now the mass scale death of the ocean animals like Olive Riddley turtles is occurring in the Odisha coast for the mechanized operations.
Whales are listed under Schedule I of the Wildlife (Protection) Act, 1972. The adult is reported to weigh around 20 to 30 tonnes. Whale and whale sharks live in tropical and warm open oceans with a lifespan of about 70 years.
(The writer is a former senior forest officer and an environmentalist. Tel no 9937460649)