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Behavioral Ecology of Cetaceans in the Southern California Bight
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A behavioral ecology perspective on cetaceans in the Southern California Bight (SCB) can contribute to science-based adaptive management in the context of expanding anthropogenic activities. Objectives were to (1) identify behaviors associated with habitat resource selection, (2) evaluate species differences related to body size, group size, and group cohesion, and (3) determine temporal behavioral patterns. Cetacean aerial surveys (87,735 km) were conducted in 2008-2013 in all months except December. Locations and behavioral data were recorded for blue whales (Balaenoptera musculus), fin whales (B. physalus), gray whales (Eschrichtius robustus), Risso’s dolphins (Grampus griseus), common bottlenose dolphins (bottlenose; Tursiops truncatus), and common dolphins (Delphinus delphis and D. capensis). Response variables (occurrence, behavioral state, group size, group cohesion) were analyzed relative to the explanatory variables calf presence, bottom depth, shore distance, slope, aspect, time of day, Julian day, season. Resource Selection Function (RSF) modeling predicted probability of habitat use relative to resource availability and behavioral state by contrasting environmental characteristics at locations of cetaceans and randomly selected points (n=35,167). During medium/fast travel, relative probability of habitat use by fin whales was highest in deep and eastern waters (p<0.05) of the San Nicolas and San Diego basins. Risso’s dolphins selectively (p<0.05) used nearshore waters more than expected relative to availability, especially San Clemente Island, and habitat use differed by behavioral state (rest/slow travel, medium/fast travel; p<0.05). Bottlenose dolphins selectively used (p<0.05) nearshore shallow waters more frequently than available, particularly near Santa Catalina Island. Behaviors varied by species, not solely by body size. Larger whales (blue, fin) and dolphins (Risso’s, bottlenose) occurred in smaller, less cohesive groups and were more likely to occur alone. Species-specific group size was larger with calf presence; cohesion was higher during peak reproductive seasons (calving/mating). Time of day influenced behavioral state in nocturnal-feeding Risso’s and common dolphins, which were less cohesive and more inactive (mill/rest/slow travel) near midday. Spatiotemporal variation in cetacean distribution may reflect short-term changes in reproductive condition, resource availability, and anti-predator behavior. Applications of this behavioral ecology perspective are discussed relative to management opportunities within the framework of protecting areas, endangered species, and species-specific sensitive time periods.
Smultea, Mari Ann (2016). Behavioral Ecology of Cetaceans in the Southern California Bight. Doctoral dissertation, Texas A & M University. Available electronically from