Mother-calf interactions during the first year of life for bottlenose dolphins (Tursiops truncatus)
The development of behavior and the nature of the mother-calf relationship during the first year of life was investigated for eight mother-calf pairs of captive bottlenose dolphin calves housed in two separate facilities. Data were gathered using two separate approaches--an ad libitum sampling approach in which every behavior observed was recorded in a diary-entry format and a scan-sampling method in which a sample point was recorded for all subjects every five minutes. Observations generally lasted 30 minutes in length. Variables of interest were mother-calf interactions, other behaviors by mothers, other behaviors by calves, and general social interactions. Specific behaviors examined for mother-calf interactions included mother-calf swims, contact, separations, reunions, proximity-maintaining behaviors, maternal discipline, maternal intervention, secure-base behavior, and nursing. Other behaviors examined included swims with others, solitary activities, object play, and orients at objects, and social interactions. Results indicated that maternal differences existed in maternal care behaviors differentiating mothers into one of three basic categories of maternal styles ranging from "permissive" to "restrictive". Calves, however, generally showed similar developmental trends for behavior and sociability regardless of the facility and individual mothers. The results were interpreted within the context of attachment theory.