Choose your language:

Whales - an Introduction

Whales, dolphins and porpoises are a group of marine mammals collectively known as cetaceans.

Scientists estimate that there are approximately 90 species of cetacean. This distinctive and charismatic group includes the largest animal that ever lived and the longest-lived mammal.  Some cetacean species demonstrate highly developed methods of communication including long and complex 'songs' and others navigate and locate their prey via echo-location, generating their own sound waves.

Cetaceans are divided into either toothed species (known as Odontoceti) or baleen species (known as Mysticeti). 

Click here to learn about classification of cetacean species.

Some toothed species have upper and lower rows of teeth, some have teeth on their lower jaw only, and the narwhal has a single, long tooth which is usually considered to be a tusk.  There are approximately 70 species of toothed cetacean.  These include killer whales, all species of dolphin and porpoise, and the sperm whale, the only toothed species of large whale.

In contrast, baleen whales have no teeth.  They filter-feed, ‘sieving’ small marine organisms such as krill through fringed plates of baleen.  Like our nails and hair, baleen is made of a protein called keratin.  With the exception of sperm whales, all the large whale species are filter feeders. Classification of species and subspecies is a dynamic discipline which constantly evolves as more information emerges, but there are currently assessed to be 14 baleen whale species. 

Baleen whales are generally known for long migrations, breeding in warm, equatorial waters in winter, and feeding in polar waters during the summer.  The whale populations of the northern and southern hemispheres don’t mix because their seasons are opposite.

The many and varied species of toothed cetacean have less uniform patterns of behaviour.  The vast majority also live in the oceans although there are some species of dolphin found in rivers and estuaries. 

Many populations of whales were hunted to dangerously low levels in the 19th and 20th centuries.  The first protections were introduced by the IWC in the 1960s and a ‘moratorium’ on all commercial whaling was implemented in 1986.  The recovery of some populations from near-extinction is a major conservation success story, but this is certainly not the case for all, and some populations remain critically endangered. Whaling has been replaced by other man-made hazards, such as bycatch, collision with ships, ocean noise, and other forms of habitat degradation, as the primary threats to cetaceans.



noun [ C ] BIOLOGY specialized

pronounce/ Cet·a·ceans
plural noun: cetaceans

a marine mammal of the order Cetacea ;
a whale, dolphin, or porpoise.


  1. They are intelligent cetacea. - Jules Verne
  2. Cetacean flukes are horizontal and move up and down, because cetacean spines bend the same way as in other mammals. - Wikipedia
  3. The enormous cetacean disappeared and reappeared as the waves rose and fell, showing its black back like a rock in open sea. - Jules Verne