The Online Library of Knowledge


Dolphins and porpoises

Bottlenose dolphinBottlenose dolphin Dolphins, like whales, are mammals that live permanently in the water. Along with whales and porpoises, they belong to the cetacean group. There are 41 species of dolphin, ranging in size from less than 1.4 metres (less than 5 feet) long to the killer whale, or orca, about 9 metres (30 feet) in length. Dolphins have a single backward-curving, dorsal (back) fin, and many species have a beak-like snout. All dolphins have teeth and feed mostly on fish or squid, which they chase through the water at speed. They have good eyesight and exceptional hearing. 

Atlantic spotted dolphinAtlantic spotted dolphin
A pod of common dolphinsA pod of common dolphins


Most dolphins are social animals. A group of 10–12 dolphins swimming together is called a pod. They sometimes merge temporarily to form larger groups, called "superpods", which can number up to 10,000.

Male dolphins are called bulls, females cows and their young calves. Pods may stay together for life. The dolphins call to one another using squeaks and clicks. Individuals frequently move between groups, but some species, such as the killer whale, form stable family pods.

Changing the type of nets used to catch tuna fish have resulted in the decrease in unintentional dolphin kills by up to 50% since the 1980s.

© 2020 Q-files Ltd. All rights reserved. Switch to Mobile