Twitter
Advertisement

Is whales 'committing suicide' a natural process or a man-made phenomenon?

With so many whales getting washed ashore, Jayadev Calamur tries to understand whether whales 'committing suicide' is a natural process or a man-made phenomenon

Latest News
article-main
FacebookTwitterWhatsappLinkedin

National Geographic report in November 2015 said that scientists discovered 337 dead whales in southern Chile's Patagonia — the biggest single whale stranding event known to science.

"Because of the remoteness of the area and the roughness of the seas, scientists have not been able to examine the whales directly, but aerial and satellite photography identified 305 bodies and 32 skeletons in an area between the Gulf of Penas and Puerto Natales, toward the southern tip of the continent," the report said.

In the past few months, news of whales being washed ashore has been reported the world over. There have been cases reported in various parts of India, the United Kingdom and New Zealand.

The beaching of dolphins, whales and other marine mammals is not a new phenomenon. Beaching instances have been reported as far back as during the time of Aristotle. Environmental activists now suggest that human impact of pollution, shipping noise and, in some cases, military sonar have led to a rise in the frequency and severity of beaching events. Scientists say the mammals may beach themselves for a number of reasons, including illness, old age and drowning when high tide blocks a whale's blowhole (through which they breathe).

In an interview with Scientific American, Darlene Ketten, a research scholar from Woods Hole Oceanographic Institution in Maine, US, said that statistically, only 50 per cent of all such cases worldwide have been determined.

"In some cases it is obvious, like a ship strike leaving an animal in poor condition. In the north-eastern United States, pneumonia is a common cause of stranding. We see other diseases and trauma, such as shark attacks on whales or dolphins or attacks by members of the same species. Poisonous 'red tides' will also affect marine mammals. Some cases have been speculated to be related to anomalies in the magnetic field," she said.

Another reason for whales getting washed ashore is the military sonar, but Ketten says that while environment groups have published releases, there is no hard evidence that sonar plays a role.

Closer home, Dr P Santhanam of the Department of Marine Sciences at Bharathidasan University in Tiruchirappalli says that whales beaching may be due to anomalies in the magnetic field. "Rough weather, water pollution (such as oil spills, eutrophication, algal blooms) and environmental toxins are other possible causes put forth by researchers. Heavy underwater activity like earthquakes or volcanoes can also disturb whales, resulting in their distress movement towards the coast," he explains.

Santhanam also adds that whales naturally move against the waves. So during ebbing, when the water recedes from the shore into the ocean, whales may get caught in a situation when there is no water left to swim in, resulting in getting beached along the coast.

Man-made problems
Marine biologists and environmentalists have suggested that pollution, noise from shipping vessels and, in some cases, military sonar have led to a rise in whale stranding and the severity of such events. "The use of man-made sonar may interfere with a whale's brain waves, causing the animal to lose its sense of direction and beach itself. Low wavelength sounds (of human origin) disrupt the whale's sonar, which also makes it difficult for them to navigate and can result in their ending up on the beach. Man-made conditions like a ship causing injury to whales or its wreckage or pollutants like sewage, industrial waste and oil spills have also been found to be a reason. Rising noise pollution in the sea is also a possible reason that causes distress movement. And the presence of plastic in the sea could choke the mammals," Dr Santhanam explains.

How it affects the ecosystem
When a whale dies, its body drops down to the ocean floor and is a great food source to all sea creatures in the lower depths of the ocean. Whale faeces too serve an important purpose in the ecosystem. The nutrients contained within the faeces help stimulate the growth of phytoplankton, which are organisms that take in carbon from the air and supply oxygen, providing a cleaner, healthier atmosphere for all plant and animal life to breathe in.
Dr Santhanam says that as much as 400,000 tonnes of carbon is extracted from the air due to these whales each year. In addition to feeding carbon-fighting phytoplankton, the fact that whale faeces stimulates the growth of phytoplankton means that it also helps feed other species feeding on phytoplankton for their survival.

Find your daily dose of news & explainers in your WhatsApp. Stay updated, Stay informed-  Follow DNA on WhatsApp.
Advertisement

Live tv

Advertisement
Advertisement