Occurrence Patterns of Bottlenose Dolphins in the Drowned Cayes Region of Belize
Kerr, K.A.¹ and Defran, R.H.²
¹,² Cetacean Behavior Laboratory, Department of Psychology, San Diego State University, San Diego, CA 92182-0350
¹ Oceanic Society Expeditions, Fort Mason Center, Bldg E, San Francisco, CA 94123
Occurrence patterns of bottlenose dolphins (Tursiops truncatus) in the Drowned Cayes region of Belize were examined during 392 photo-identification surveys conducted between February 10, 1997 and December 4, 1999. Dolphins were encountered on 82% (n=320) of all surveys. Size of the 681 schools encountered ranged from 1 to 20, with a mean of 3.0 (SD=2.32). Sighting frequencies for the 118 photographically identified individuals ranged from 1 to 54 (mean=8.9, SD=10.11). Seventy-five percent (n=89) of the identified dolphins were photographed more than once and 58% (n=68) were photographed on five or more occasions. New individuals continued to be identified throughout the study (mean discovery rate=4.2 individuals/10 surveys, SD=4.48). Examination of sighting histories by season showed that 99% (n=71) of dolphins sighted four or more times (n=72) were seen in more than one season, and 56% (n=40) were seen during all four seasons. The presence of some individuals (34%) in the study area across all seasons suggests a pattern of local, although possibly short term, residence, while the 25% of the population photographed only once indicates limited occurrence in the area for some individuals. Photographic comparisons were made between the Drowned Cayes catalog and 81 individuals from a four-year (1992 to 1996) data set collected at Turneffe Atoll located 16 km away from the Drowned Cayes. Despite the close proximity of the two areas and the apparent occasional use of each area by a high proportion of identified dolphins, no overlap in the photographic catalogs was found.
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