Resighting and association patterns of bottlenose dolphins (Tursiops truncatus) in the Cedar Keys, Florida: insights into social organization

Little is known about the social organization of bottlenose dolphins (Tursi ops truncatus) inhabiting open estuarine systems. Our purpose was to identi fy and quantify the resightings of bottlenose dolphins and associations for med among them to provide insights into the social organization of the spec ies in the open estuarine system of the Cedar Keys, Florida. We conducted m onthly photographic-identification surveys from June 1996 through May 1997. We identified a total of 233 dolphins of which 217 (93%) were classified i nto one of four categories based on the number of months in which they were sighted. "Rare" dolphins (sighted during 1-2 months) constituted more than half of these individuals (61%), followed by "occasional" (3-5 months; 20% ), "common" (>8 months; 12%), and "frequent" (5-6 months; 7%) dolphins. We quantified the associations for dolphins sighted 10 times (26 common, 12 fr equent, and 8 occasional) and found that individuals with different resight ing patterns associate with each other but the association is mostly at a l ow level. The level of association among common dolphins, however, was high er within than between the sexes. Association patterns of common dolphins i n the Cedar Keys resemble the associations of resident bottlenose dolphins inhabiting closed estuarine bays, suggesting that the selective pressures w hich induce such associations are the same in these aquatic systems.