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