Dolphins--Behavior

This investigation is the first to focus on the underwater behaviors and development of free-ranging Atlantic spotted dolphin (Stenella frontalis) mothers and calves. Underwater video recordings of 30 mother/calf pairs, during the calves' first three years of life, and 10 additional videos of four-year-old calves, were analyzed. Behavioral event frequencies were compared to the calf's age bracket (i.e. year-one, two, three and four). Results demonstrate an increase in calf independence in year-four shown by a significant reduction in Nursing Act behaviors, significantly more Feeding/Foraging behaviors, and increased behaviors performed in the proximity of individuals other than the mother or alone. No strong evidence was found for increased maternal rejection behaviors near the end of the estimated weaning period. Additionally, results indicate that, for select behaviors, synchronicity may be increasingly expressed over time. Few differences in behavioral frequency and type were observed between calf genders and between mothers of each gender.

This study documented the behavioral development of Atlantic spotted dolphins (Stenella frontalis) in the Bahamas. 45 three-minute video-taped sequences of underwater social behavior (aggression, courtship, play), spanning from 1992 to 1996, were selected for ethological analysis and were broken down into 15 adult, 15 juvenile and 15 mixed age class sequences. Continuous focal sub-group sampling was conducted, and one-tailed Kruskal-Wallis ANOVAs were used to test for differences between the age groups in frequencies of occurrence of: (1) the 7 behavioral categories, and (2) the 8 most frequently performed behavioral events. Juveniles performed significantly more Other behaviors and Attention to Object events than adults, suggesting the importance of play within this social species. A Mann-Whitney U test revealed that within mixed age classes, behaviors were performed within combined-age-class groups more often than within single-age-class groups, suggesting a participatory mode of learning within juveniles.