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- Title
Occurrence, distribution, site fidelity, and school size of bottlenose dolphins (Tursiops truncatus) off San Diego, California
- Authors
Weller, David W.; Defran, R. H.
- Abstract
The occurrence, distribution, site fidelity, and school size of bottlenose dolphins (Tursiops truncatus) in the coastal waters of north San Diego County, California were assessed during a six-year boat-based photoidentification study. A total of 146 photographic surveys wereconducted between January 1984 and December 1989. Dolphin schools were encountered on 79% of all surveys, and 2,869 individuals were observed in 145 separate schools. Three-hundred seventy-three dolphins were individually identified. All schools were sighted within 1 km of shore, and more than two thirds of the schools were encountered in thesouthern half of the 32-km long study area. School size (mean = 19.8, SD = 18.40) and the number of dolphins encountered per survey (mean= 26.8, SD = 22.30) were highly variable. Low resighting rates of known individuals provided little evidence for long-term site fidelity.When our six-year photoidentification database was combined with previous data, 404 dolphins were identified in the study area from September 1981 to December 1989. Jolly-Seber population estimates during the 1984-1989 study period varied between 234 and 285. The combinationof regular dolphin occurrence, low site fidelity by known individuals, and the continuous increase in the rate at which new dolphins wereidentified indicates that numerous different individuals were visiting the study area across and within years. The open California coastline differs in habitat structure and prey distribution from more protected study areas where bottlenose dolphins display site fidelity. These habitat differences may help to explain the observed intraspecific behavioral variability of this species.
- Subjects
CALIFORNIA; SAN Diego (Calif.); UNITED States; BOTTLENOSE dolphin; MARINE mammals; SCHOOL size; POPULATION dynamics
- Publication
Marine Mammal Science, 1999, Vol 15, Issue 2, p366
- ISSN
0824-0469
- Publication type
Article