The Social Structure of Marine Mammals

What is their family structure?

Their complex social structure is another survival tactic that gives their slow-growing offspring time to learn and grow in the safety of their mother's pod. The mother is often assisted during birth by an "auntie" or a "midwife" who makes sure the newborn calf gets to the surface to take its first breath.

Photo: credit Bill Curtsinger Photography

According to the Dolphin Research Center, Dolphins tend to be very social animals, swimming in social groupings called pods.

These groups, however, are very flexible and fluid, not at all like the social unit we refer to as a family. Dr. Deborah Duffield has determined by observing pods of wild bottlenose dolphins that the majority of pod members are not closely related. They seem to be in a periodic state of flux; an individual dolphin traveling with one group may be swimming miles away with another by the next day. A more stable subgroup of two to six dolphins may remain together over long periods. Mothers and their calves have been observed together for at least three to six years, and unrelated adults often form long-term bonds, usually within the same sex and age group.

Separation by age and sex is common. Breeding groups are usually composed of mothers and their calves. As the youngsters begin to mature, they may branch off into a juvenile pod.

Mature males will rarely be seen mixing with a maternity pod or a juvenile pod. The fluidity of the groups, however, allows increased opportunities for mating, enabling males to court a wider variety of females. During feeding, smaller pods may interact and join into larger groups. Bottlenose dolphins also have been observed swimming and feeding with other cetaceans such as sperm whales, gray whales, humpbacked dolphins, and right whales.

Since 1970, Dr. Randall Wells of the Mote Marine Laboratory and his colleagues have studied generations of wild bottlenose dolphins around Sarasota, Florida. They have provided valuable information on group behavior and mother-child bonding in wild populations. They have identified 3 main groupings, or pods, of dolphins:

Mothers and juveniles

Young dolphins typically stay with their mothers for several years, three to six years or even longer. Even after they leave their mother's pod, they may return for a visit, and daughters often return when they have their first child.

Bands of juveniles

Generally these pods consist of young dolphins between the ages of three and thirteen. Here, two males may often form strong bonds that may last 10 to 15 years or longer.

Adult males

These male dolphins travel from one pod to another, staying for short periods of time and then moving on.