Comportamento de cuidado parental na população de Sotalia guianensis na Baía de Sepetiba, RJ

Abstract

Previous studies in Sepetiba Bay, RJ, recorded calves and juveniles of Guiana dolphin through all seasons. However few is know about the behaviors of parental care for this species. The main objective of this work was to investigate the behavior of parental care in Sotalia guianensis population of Sepetiba Bay. The film clips used in this study were recorded in 30 boat trips conducted in the bay from December 2000 to August 2001. The evaluation of the parental care degree was conducted using two measures: longitudinal care and transversal care. When the mother located itself longitudinally ahead of its offspring (longitudinal position 1) or when it was between the boat and the offspring (transversal position 1) the parental care were registered. However, there was not care when the mother located itself behind its offspring (longitudinal position 2) or when the mother left its offspring to be between the boat and it (transversal position 2). The influence of three variables was tested: group size, behavior state of the group (feeding and traveling) and age class (calve and juvenile). From the total of 39,840 second of observation, 946 mother-calf dyads were recorded, and the results of the analyses of the kinds of care conducted separately revealed that the longitudinal care was present in 84.7% of the time and the transversal care in 57.7%. The time spent by the offspring on each longitudinal position (1 and 2) was statistically different (U=58,033.50; p=0.02), receiving care during the median of 37 seconds. About the transversal care, there was not significant difference in the time that offspring received care. The group size was statistically different when the mother located itself longitudinally ahead of its offspring or not (U=151,525.50; p<0.01), the median of group size for position 1 was 15 individuals, while for position 2 was 12. In relation to the mother position between the boat or not, there was also significant variation (U=97,074.00; p=0.03), the median of group size for transversal position 1 was 15 individuals and for position 2 was 14 animals. Was identified significant influence of the behavior state of the group on longitudinal care, and that care is intensely performed at feeding (N= 946; H3=17.60; p<0.01). The immatures of Sepetiba Bay population have benefited from intense parental care, mainly during the feeding activities and in large groups. The care is similarly offered to calves and juveniles, longitudinally and transversally, suggesting a parent-offspring conflict of interest.