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The social dolphin swims in groups known as pods. These pods vary in size, but most are composed of between 2 and 30 individuals. Smaller dolphin species swim in larger groups than larger animals do. Since young dolphins grow slowly, pods provide protection for the young, as well as strength in numbers to protect the animals from sharks and other predators.
Pod structure is fluid, and individuals move in and out of various pods depending on the time of day and purpose of the grouping. Observations of wild bottlenose dolphins, for example, reveal that most pod members are not closely related. Pod size tends to increase when the dolphins are in deeper, more open waters. While the individuals within the larger pod fluctuates, pairs and small groups of dolphins may swim together for many years. These bonded pairs are usually the same sex and of similar ages.
Female dolphins and their calves form nursery pods. A mother and her calf stay together for between three and six years. Female dolphins who have bonded with each other swim together to help care for and protect their young. Although all calves leave their nursery pod as juveniles, they return periodically to swim with their mothers. When young females are pregnant, they often join their natal nursery pod to birth and raise their calves with their mother and other female relations. Adult male dolphins are rarely seen near nursery pods.
Both male and female dolphins between 3 and 13 years of age swim together in juvenile pods. Although they still interact with adults, young dolphins associate most often with other individuals their own age. During this time, they spend most of their time socializing. Juvenile male and female dolphins also engage in mating behavior while in juvenile pods. Relationships between males and females are short-lived, however, and when a young female becomes pregnant for the first time she joins a nursery pod of other females.
While in a juvenile pod, a young male dolphin often forms a pair bond with another young male. These relationships are very close and cooperative. Two bonded male dolphins may swim together for a decade or longer. Adult male dolphins are the most transient of dolphins, frequently moving from one pod to another. Large males swim at the outer edges of more sizable groups, possibly to protect the pod as a whole.
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