Date of Award

Spring 2010

Degree Type

Masters Thesis

Degree Name

Master of Arts (MA)



Committee Chair

Stan Kuczaj

Committee Chair Department


Committee Member 2

David Echevarria

Committee Member 2 Department


Committee Member 3

John Harsh

Committee Member 3 Department



The study of cetaceans in captivity provides information on behavior, acoustics, reproduction and physiology that is often difficult to obtain with free-ranging populations. The present study examined the influence of the estrous cycle of a captive female killer whale on the rate, duration, initiation and reception of social behavior she performed with her only pool mate, a male Atlantic bottlenose dolphin. Although these two delphinid species do not commonly associate in the wild, these pool mates often engaged in affiliative tactile and social behaviors. The objectives of this project were to: (a) examine the influence of cycli~ gonadal steroid hormones on social behavior in the killer whale, and (b) document a rare interspecific interaction. A total of five estrous cycles, covering the span of eight months, were analyzed in the present study. Weekly blood serum samples from the female killer whale were analyzed to ascertain the estrous cycle phase of this focal subject. Hormonal data was then compared to opportunistic video footage of the subjects' interaction. Based on previous reproductive endocrinology studies, it was hypothesized that the female killer whale's initiation of such behaviors would increase during the fertile window of behavioral estrus. The average rate of female-initiated tactile behavior, female-to-male chasing, and pair swimming was significantly higher during the luteal phase than the follicular phase, with a peak in such behaviors occurring more than a week after the fertile window. In addition, the average duration of female initiated tactile behavior was significantly longer during the luteal phases. Male-initiated social behaviors did not significantly change in rate or duration throughout the focal subject's estrous cycle, suggesting that the male bottlenose was not perceptive to the killer whale's hormonal cycling. Furthermore, the average duration of resting by the female subject did not significantly change throughout the estrous cycle, suggesting that the increase in socially proceptive behaviors is most likely not a byproduct of an overall increase in general activity level due to a hormonal surge following ovulation.