| The Southern California Bight has one of the most diverse and abundant marine mammals populations in the world. Baleen whales, toothed whales and different species of pinnipeds inhabit this area either as seasonal visitors, migrants or residents. Within the Bight, Santa Monica Bay represents a region with unique topographic and oceanographic features which affect the ecology of the three resident species of dolphins (common bottlenose dolphins, Tursiops truncatus, short-beaked common dolphin, Delphinus delphis, and long-beaked common dolphins Delphinus capensis ). Boat-based surveys were conducted from January 1997 to December 2001. Behavioral data collected ad libitum in 1996 provided a framework of information to design the sampling procedures systematically adopted from January 1997. Data recorded with laptop computers included: species and number of animals, size class, group formation, surfacing mode, directional behavior, behavioral states, boat disturbance, and association between species. Dolphin photo-identification was performed during all four seasons in 1997–2001 and videos were recorded to investigate the animal behavior a posteriori . This dissertation describes (1) occurrence, seasonality, spatial distribution, sympatry, and habitat partitioning of different cetacean species in relation to the environmental features of the bay, (2) social ecology of the most regularly observed species, (3) changes in the distribution, seasonality, relative abundance and species composition of marine mammals before, during, and after the strong 1997–1998 El Niño event and following La Niña, and (4) aggregations between dolphins and sea lions and their respective or combined foraging behavior. Additionally, this work offers a final general review on dolphin sympatic ecology. |
