Social behaviour

All dolphins are essentially social animals, it has evolved to be a benefit for all the members of a group. The influence of the habitat on group size is quite easy to see among dolphins. River dolphins such as the Indus and Ganges river dolphins, are among the least social of all the dolphins. Often living an almost solitary existence, they seldom congregate in groups of more than ten. This is because they inhabit shallow rivers in which their prey is distributed more or less evenly.

Coastal dolphins, such as the tucuxi, benefit in the same way as river dolphins from the varied topography of their habitat, but, at the same time, predators are more numerous here, and the dolphins' own prey tends to be more scattered. To protect themselves while they range further in search of prey, these dolphins tend to form social groups, typically 5-20 individuals.

Group size

The open-ocean dolphins, such as the spotted dolphin, live in the open, often featureless, waters quite unlike any terrestrial habitat. The threat from predators, such as sharks, is much greater and while the dolphin's prey tends to be concentrated in groups they are widely distributed. For these dolphins the benefits of group living are even greater and, as a result, they typically congregate in schools of a 100 or more. By co-operating with each other they can split up and search vast areas of the ocean for prey. Similarly, with so many pairs of eyes and ears to keep watch for predators, the chances of an individual being taken unawares by a stealthy shark are greatly reduced.

The fundamental social group is that of mother and calf. Calves are seldom weaned before they are about four months old and may continue to suckle for many years. This establishes a bond that is often maintained even after the calf matures. Males, on the other hand, are often peripatetic - they move from place to place, spending short periods of time with a number of different groups of females and young. (For more information about pregnancy and birth please go to the pregnancy and birth section in Life cycle).

Social Status

There is a clear social status within dolphins as have been noted with studies of the bottlenose dolphins. Like wolves in a pack, size is usually the key factor determining rank, but an individual's status appears quite fluid, changing with health, reproductive ability and the presence of other group members. And like their canine counterparts, dolphins also exhibit various kinds of behaviour to assert their dominance over rivals, including biting, ramming, jaw clapping, tail slaps and body checks. The play behaviour of dolphins probably has more to do with learning social skills and acquiring the necessary agility to pursue prey than social status.

Pods of dolphins leap, tumble, back flip and spin together; and there is often no explicable reason for their behaviour other than pure social enjoyment. Dolphins will race towards boats to surf in the bow wave or play in the wake performing amazing acrobatics. Some dolphins seek out big waves breaking close to shore and ride the waves alongside surfers, other dolphins prefer to play with plants or shells or other make-shift toys.

Dolphin Play

Dolphins also enjoy a game of catch, perhaps with a fish or even a turtle, throwing the animal back and forth to each other. There are also activities similar to “tag’, one dolphin will nudge another a few times to indicate its willingness for a game, then high-speed pursuit will take place through the sea, as they take turns chasing each other. Some dolphins have teamed up with other animals. Bottlenose dolphins and humpback whales have been seen playing together where the dolphins swim onto the nose of the whales, which then raise themselves out of the water to a great height. The dolphins slide down their heads with a great splash. As the game is repeated over and again, it seems clear that both individuals are enjoying it.

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