Acoustic communication in bottlenose dolphins.

This thesis examines the behavior and acoustic communication of bottlenose dolphins in Shark Bay, Western Australia. The thesis begins with a review of the literature on dolphin acoustic communication, followed by background information on the Shark Bay dolphin research project and general methods. Chapter two examines patterns of association among individuals. Groups of dolphins (2-20 individuals) were fluid with frequent changes of membership. Underlying these temporary associations were long-term, consistent associations between members of the same sex. Males associated with one or two other males, stable over years. Male-male associations were as consistent as those between mothers and their dependent offspring. Female-female associations were less consistent, but some stable associations occurred. This fission-fusion social organization is compared to similar patterns in chimpanzees and spider monkeys. The third chapter examines how associations between mothers and calves are mediated through the use of individualized signature whistles. Focal infant follows with simultaneous acoustic monitoring revealed that infants frequently separate far from their mothers and produce distinctive whistles primarily during the process of reuniting. The use of signature whistles to mediate mother offspring reunions is compared to other species exhibiting similar acoustic and social systems, particularly colonially living birds and mammals. The fourth chapter presents analysis of whistle repertoires of six provisioned dolphins that regularly enter shallow water at the Monkey Mia campground where they are fed by hand. Females produced 1-4 whistle types per dolphin, and whistle repertoires changed little across the three years of the study. Males produced 5-14 whistle types, and year to year changes occurred in the repertoires of the two males recorded in multiple years. The males shared several whistle types, and they converged on a single whistle type, which became the most abundant in their repertoires by 1987. This convergence corresponded with formation by the males of an active alliance to herd females cooperatively. The fifth chapter presents some further observations of whistle patterns and behavioral correlates of whistling. The concluding section summarizes results and discusses these in terms of possible functions of dolphin whistles.PhDBiological SciencesPsychobiologyPsychologyZoologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/129162/2/9332904.pd