Newborn characteristics, patterns of motoric and social behavioural development, and mother-infant relationships in free-ranging and semi-provisioned bottlenose dolphins (Tursiops sp.) are examined. Nine newborns were observed for 189 hours over the first 10 weeks of life. Newborn infants breathe more often than their mothers, and synchronize their breathing and swimming with her soon after birth, but show a gradual decline in synchrony as they age. Virtually all patterns of infant behaviour, mother-infant proximity, and spatial relationships with the mother changed as a function of infant age. Maternal activity, however, does not change over time, except that mothers decrease their role in maintaining proximity to their infants from the first month to the second month of infant life. Infants spend less time close to their mothers, less time echelon swimming (close, alongside the mother), and more time infant-position swimming (in contact under the mother) as they age. Infants spend more time traveling and socializing independently over time. They also separate from their mothers more often and for longer periods of time. Infants do not forage during the newborn period, but are observed 'practice foraging' by the end of the first month. Rubbing, petting, chasing, and displaying with other animals (including the mother) were common forms of socializing. Infants frequently initiate rubbing with their mothers, with particular focus on her head region. Infants typically associate with young females, adult females and other infants, but not with adult or subadult males. Developmental shifts and overall patterns are discussed in the context of the bottlenose dolphin's fission-fusion social organization and ecology. The effects of provisioning on dolphin behaviour are addressed.