GROUP CHARACTERISTICS AND SOCIAL AFFILIATION PATTERNS OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN THE INDIAN RIVER LAGOON, FLORIDA

• Published in: Florida scientist Vol. 71; no. 2; pp. 149 - 168
• Main Authors: Kent, Erin E., Mazzoil, Marilyn, McCulloch, Stephen D., Defran, R. H.
• Format: Journal Article
• Language: English
• Published: Orlando The Florida Academy of Sciences, Inc 01.04.2008; Florida Academy of Sciences, Inc
• Subjects: Calves; Dolphins; Foraging; Freshwater; Group size; Lagoons; Marine; Mating behavior; Mothers; Predators; Sharks; Social structures; Tursiops truncatus; ASW, USA, Florida, Indian River Lagoon
• ISSN: 0098-4590
• DOI: 10.1043/0098-4590(2008)71[149:GCASAP]2.0.CO;2

A long-term investigation of the group characteristics and social affiliation patterns of Atlantic coast bottlenose dolphins was carried out in the Indian River Lagoon (IRL), Florida. Group characteristics and photo-identification data were collected during 477 boat-based surveys conducted in the IRL from 1996 to 2004. A total of 2,132 groups were encountered and photographed over the study period. Group size averaged 4.1 (SD = 3.43) and did not vary by season, but was higher during some yearly periods, and for sightings in the afternoon than in the morning. Further, groups with at least one calf (x̄ = 5.5, SD = 3.80) were larger than groups without calves (x̄ = 2.4, SD = 1.85). Overall, half-weight Coefficients of Association (COA) indices for these frequently sighted dolphins ranged from 0.09 to 0.83 (maximum values), showed that they preferentially associate and that associations were higher within sex class than between sex class. In the aggregate, IRL group characteristics mirrored those found in other southeastern U.S. bays and estuaries and suggest that similar behavioral processes are important across these different locations. These processes include: resource and habitat optimizing while foraging and forming affiliations, and developing a balance between the demands of foraging, predator defense and maternal care.