Whales overcome seasonal changes in their environment by moving annually with changing ocean conditions and prey densities.
The sun shines brightly over a placid sea. All of a sudden, a fountain of water breaks the surface! Whoosh! First a flipper, and then a gloriously large tail appear and disappear into the blue! That is just a dancing whale for you!
These aquatic mammals are widely distributed across the globe. They usually feed on plankton, krill, shrimp, small squids and other small marine creatures. Whales are of two types: odontocetes - toothed whales such as dolphins, orca and sperm whales; and mysticetes (also called baleen whales) - whales possessing a sieve-like comb to filter their food from the water, such as the humpback, blue and right whales.
Charting the route
Whales overcome seasonal changes in their environment by moving annually with changing ocean conditions and prey densities. Baleen whales swim to poles to feed in the plankton-rich cold waters during summer, and to more tropical, warm waters in winter to give birth. Toothed whales, on the other hand, move seasonally in a north-south direction, or offshore-inshore.
However, it is often found that whales do not necessarily migrate just in search of food. Sometimes, they do so to give birth in waters that are comfortable for the newborn calves. Other times, they migrate to save their calves from predators like killer whales (also called orca). Whatever the drivers may be, whales swim astounding distances with routes criss-crossing ocean basins.
Have you ever wondered how these amazing creatures navigate the murky depths of the ocean? Even in deep waters, tagged whales are found to travel long distances in perfect straight lines, indicating excellent navigation abilities. They are able to orient themselves with extreme precision over large expanses of featureless water surfaces, despite interference by strong ocean currents and weather phenomena.
That some individuals have in fact returned by a different route pays further tribute to their skill. Scientists feel that it is unlikely that such impressive and precise navigation can be explained purely by magnetic and solar orientation cues. It seems reasonable to believe that whales employ alternate mechanisms alongside established models of directional orientation.
In the aquatic medium, sound waves travel far better than light. Acoustic communication, therefore, is decidedly more effective than visual means in the marine environment. It is well known that vocalisations play a major role in communication between whales. 'Whale songs' involve repetitive, long, low frequency calls. Certain species, especially the bowhead and the humpback, are highly vocal during migration.
Some species of whales communicate using non-song sounds which they make by slapping and breaching the water surface. Social vocalisation using such sounds is an important part of communication between and within splitting and merging herds.
With globally increasing temperatures, migrating whales are already facing longer journeys and reduced feeding opportunities as favourable bioclimatic zones inch polewards. Should we add more to their long journeys?