During warm weather, the belly is often a flushed pink color which is thought to be in response to the warm water. Recognizable marking or characteristics, such as dorsal fin scars or notchings can identify different individuals. Repeated sightings of these individuals provide information about home-range limits and group composition. The average lifespan is estimated to be about 25 years, although some live to their late 40's. Dolphins may be aged by the presence of growth layers in their teeth, much like the aging of a tree from its rings.
Females bear a single calf every two or three years and gestation is about twelve months.
Calves are nursed for a year or more, yet stay with their mothers for up to five years. During this extended period of dependence, calves spend their time learning practical skills such as how to find and capture food, how to recognize other dolphins, and who fits where in the dolphin social hierarchy. Coastal bottlenose dolphins are found in smaller groups than offshore ones. Ecological pressures, like predation and foraging, are probably the driving factors for group sizes. However, there may be some degree of segregation based on age and sex, at least in some areas.