How is noise pollution killing whales?

There are many reasons behind whales meeting their death on the shores. Sometimes they lose their way and move towards the beach. Some whales, swimming too close to the shores, are beached when there’s steep decline in water level during low tide. Whale is endowed with a natural compass in its head. This compass, which works on the basis of Earth’s magnetic field, helps it to navigate through the sea. Unfortunately for the whales, the magnetic field is not the same everywhere. It is greater near the poles and weaker near the equator. It affects the whales’ built in compass which does not work perfectly in areas where the magnetic field is weak. Many a times the whale unknowingly approaches the sea shore due to navigation error and if it is stranded on the land, there is no chance for its survival. Its body collapses under its own weight and soon it dies of dehydration.
Beached whales
While the whale navigates using its natural compass, it finds its way under the water using its natural sonar. The whale emits high-pitched sound waves in the water. These waves bounce back from the sea-bed (or predator) and upon receiving them the whale decodes its route. This way of finding the directions is known as echolocation; and it works perfectly when the sea is calm.
Unfortunately, seas around the world are not as peaceful as they used to be a few decades ago. There has been a great increase in the level of noise pollution in the seas and oceans across the globe due to industrialization. Drilling of deep sea oil wells creates a deafening sound under the water. Propellers of giant military as well as cargo ships, submarines, oil tankers etc. produce jarring sounds. Military submarines’ and ships’ sonar equipments transmit low-frequency sound to locate the enemy ship or submarine. This sound is not less than 230 decibels — nearly twice the sound produced by jet engine of a combat aircraft.
All these factors add to the ever increasing levels of noise pollution in the sea. The natural sound waves emitted by the whale in order to map its route through the water therefore get scattered. The whale cannot receive them back. It loses its course due to lack of mapping, and sometimes swims towards the shallow shores — only to meet a painful death. While about 360 whales died due to beaching in 1994, the figure rose to 782 in 2004, and 2,000 in the year 2010. This clearly indicates the increase of noise pollution by humans in the ocean water. This also indicates to what extent human interference with environment can cause damage to the ecology.

Additional reading:
Beached whale (Wikipedia)

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