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

Abstract

Little is known about the social organization of bottlenose dolphins (Tursiops truncatus) inhabiting open estuarine systems. Our purpose was to identify and quantify the resightings of bottlenose dolphins and associations formed among them to provide insights into the social organization of the species in the open estuarine system of the Cedar Keys, Florida. We conducted monthly photographic-identification surveys from June 1996 through May 1997. We identified a total of 233 dolphins of which 217 (93%) were classified into 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 frequent, and 8 occasional) and found that individuals with different resighting patterns associate with each other but the association is mostly at a low level. The level of association among common dolphins, however, was higher within than between the sexes. Association patterns of common dolphins in the Cedar Keys resemble the associations of resident bottlenose dolphins inhabiting closed estuarine bays, suggesting that the selective pressures which induce such associations are the same in these aquatic systems.

Ranging patterns of common bottlenose dolphins Tursiops truncatus in Barataria Bay, Louisiana, following the Deepwater Horizon oil spill

“…In the northeastern GoM, from St. Vincent Sound to Alligator Harbor, Tyson et al (2011) identified 2 year-round, parapatric communities of dolphins, differing in the degree of site fidelity of individuals (28.3 vs. 45.7% transients). Quintana-Rizzo & Wells (2001) examined resighting patterns for dolphins in the open estuarine system of Cedar Keys over a single year, and re ported that 19% of dolphins were observed over 5 mo or more, while others were seen less frequently.…”

Group size and composition of Tursiops truncatus (Cetacea: Delphinidae), in a coastal insular habitat off southeastern Brazil

“…The individuals sighted were classified into four age categories based on their behavior and size estimates (BEARZI et al, 1997;SMUTS, 1998;CONNOR et al, 2000;MANN et al, 2000;QUINTANA-RIZZO;WELLS, 2001;CAMPBELL et al, 2002): (a) neonate -< 1/3 of adult size, presence of fetal folds, immature swimming, stereotyped surface respiration, frequent and non-coordinated head-butting against the water; (b) calf -1/2 of adult size, typical dislocation behind the dorsal fin of the presumed mother; (c) juvenile -2/3 of adult size; and (d) adultapproximately 3 m in length.…”

Inter-individual association levels correlate to behavioral diversity in coastal bottlenose dolphins (Tursiops truncatus) from the Southwestern Gulf of Mexico

“…Photographic data were also used to compute half-weight (i. e. controlled for sighting frequencies) coefficients of association (COA) for each dyad (pair of individuals; e. g. Smolker et al 1992;Bräger et al 1994;Félix 1997;Quintana-Rizzo and Wells 2001;Rogers et al 2004) using SOCPROG 2.4 (Whitehead 2009). COA values range from zero for dolphins that are never seen together, to one for a pair that is always seen together.…”

“…COA values range from zero for dolphins that are never seen together, to one for a pair that is always seen together. COA values were categorized as infrequent (0.0 -0.2), casual (0.2 -0.4), fair, (0.4 -0.6), moderate (0.6 -0.8) or strong (0.8 -1.0; Smolker et al 1992;Quintana-Rizzo and Wells 2001). Also, to prevent the occurrence of artificial dyads (i. e. individuals photographed together by chance due to our inclusive definition of group), a preferred/avoided partner assessment was developed through a permutation test Bejder et al 1998;Gero et al 2005).…”

“…Several communities of the coastal form of this species are known to present segregation related to sex, age and reproductive status, thus the nature of their associations is highly variable (Wells et al 1987;Wells 1991;Connor et al 1992;Smolker et al 1992;Connor et al 2000;Quintana-Rizzo and Wells 2001;Morteo et al 2014). Living in social groups facilitates feeding, protecting against harassment, predation, enhances reproductive output, and promotes communication and learning (Bräger et al 1994).…”