Bottlenose Dolphins
(Tursiops truncatus)


Dolphins exhibit much assistance and care-giving behaviour in con- and interspecific situations. For example, dolphins have been seen to help individuals in distress by either remaining by their side until they recover, or by actively bringing them to the surface of the water to allow them to breathe. They also slow their travelling pace to allow injured members of their pod to keep up. Furthermore, dolphins and other cetaceans have been witnessed placing themselves in between a distressed individual and the source of danger, or even attacking the source of danger (Connor and Norris, 1982). The fact that such assisting behaviour occurs across species led Connor and Norris (1982) to hypothesise that bottlenose dolphins are reciprocal altruists.

The pod or school unit is very fluid, but within these schools, there is much repeated interaction and opportunity for many repeated encounters. Furthermore, within a fluid school of dolphins there are less temporary associations, such as within the herd. The herd creates a situation where individuals can recognise each other and remember each other’s actions, two of the requirements for reciprocal altruism to work. Since the herd structure allows individuals to recognise and punish cheaters, Connor and Norris (1982) sensibly assumed that reciprocal altruism occurs among dolphin populations. However, they failed to consider the relatedness of the individuals within the herd.

Calves remain in close physical proximity to their mothers for upto 6 years. When they have been weaned at 12 to 18 months, juveniles may remain with their mothers for upto 4 years. Males then leave to become solitary or form an association with another male. Females, however, are likely to stay with their mothers, so that a herd may be composed of sisters, their mother and possibly aunts, if the mother remained with her sisters. Therefore, direct and kin selection are a more likely explanation for the evolution of assistance behaviour among bottlenose dolphins.

On the other hand, Tursiops exhibit helping behaviours toward other species of dolphin, and other cetaceans. Several species of dolphin and other cetaceans may have overlapping home ranges where they encounter the same individuals repeatedly, such that a mechanism for reciprocal altruism could indeed have become an evolutionary adaptation. The only mystery remaining is whether dolphins actually do help non-cetacean species such as humans, and if they do indeed do so, why