Range Characteristics of Pacific Coast Bottlenose Dolphins (Tursiops Truncatus) in the Southern California Bight

A bstract Boat‐based photoidentification surveys of bottlenose dolphins ( Tursiops truncatus ) were conducted from 1982 to 1989 in three discrete coastal study areas within the Southern California Bight: (1) Santa Barbara, California; (2) Orange County, California; (3) Ensenada, Baja California, Mexico. A total of 207 recognizable dolphins were identified in these three “secondary” study areas. These individuals were compared to 404 dolphins identified from 1981 to 1989 in our “primary” study area, San Diego, California, to examine the coastal movement patterns of bottlenose dolphins within the Southern California Bight. A high proportion of dolphins photographed in Santa Barbara (88%), Orange County (92%), and Ensenada (88%) were also photographed in San Diego. Fifty‐eight percent ( n = 120) of these 207 dolphins exhibited back‐and‐forth movements between study areas, with no evidence of site fidelity to any particular region. Minimum range estimates were 50 and 470 km. Minimum travel‐speed estimates were 11‐47 km/d, and all dolphin schools sighted during the study were within 1 km of the shore. These data suggest that bottlenose dolphins within the Southern California Bight are highly mobile within a relatively narrow coastal zone. Home‐range dimensions and movement patterns for many vettebrate species are influenced, in part, by variation in food resources. The unique range characteristics documented during this study may reflect the highly dynamic nature of this coastal ecosystem and the associated patchy distribution of food resources available to these bottlenose dolphins.