Campbell, G. S., B. A. Bilgre and R. H. Defran.  2002. Bottlenose dolphins (Tursiops truncatus) in Turneffe Atoll, Belize: occurrence, site fidelity, group size and abundance, Aquatic Mammals, 28.2:170-180.


Bottlenose dolphin (Tursiops truncatus) occurrence, site fidelity, group size, and population size were assessed within Turneffe Atoll, Belize, Central America during a 4-year photo-identification study.  Five hundred and forty-nine photographic surveys were conducted between March 1992 and March 1996.  Dolphin groups were encountered on 83% of surveys, and 2782 dolphins were observed in 732 separate groups.  Group sizes (mean = 3.8, SD = 3.55) varied both annually and seasonally.  Groups with calves were larger than groups without calves.  Eighty-one dolphins were photographically identified, and the majority (81%) of these dolphins were documented by the 150th survey in which one or more identifiable dolphins were successfully photographed (June 1993).  Sighting frequencies (mean = 12.2, SD = 14.33) ranged from one to 57, with 20% of the photographed population sighted only once and 37% photographed ≥ 10 times.  Dolphins photographed ≥ two times in at least three of the four study years were labeled as residents, and comprised 30% of the identified population.  Identified females (n = 16) and males (n = 10) had similar residency patterns.  Abundance estimates, derived by using Chao’s Mth closed method, were similar for the first (Mth = 82) and second (Mth = 86) halves of the study.  Small group sizes, low abundance estimates and the limited residence pattern observed for dolphins in Turneffe Atoll suggest that they depend on low-density food resources.  Governmental and non-governmental concerns over potential human impacts on Turneffe’s marine environment appear to be well placed.

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