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

John Harsh

Committee Member 2 Department


Committee Member 3

Kathleen Dudzinski

Committee Member 3 Department



Agonistic behavior is often observed in animal groups in which individuals have long-term relationships. Although bottlenose dolphins (Tursiops sp.) are known to behave aggressively, relatively little is known about such behavior among wild animals. Much of the data on delphiilid aggression comes from captive studies, and is likely biased by the limited space available to the animals. In this study, video data collected from 1997 to 2007 were analyzed to examine aggressive behaviors in a wild population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) off the coast ofMikura Island, Japan. The purpose of the study was to determine if age class, sex, approach angle, and body posture influenced aggression within this population. The area of the recipient's body towards which aggression was directed was also examined to determine which body parts were most commonly attacked, if any. Neither age class nor sex predicted t11e type of aggressive behavior nor influenced the duration of the aggressive bout. However, adult initiators aggressed more toward females than males. Additionally, bouts involving females were more likely to consist of a more severe type of aggression, regardless of whether the involved female was the initiator or the receiver of the aggressive act. Headto- head approaches were directed most often toward the rostrum, while perpendicular approaches were most often directed toward the sides. Additional research on other wild populations is needed in order to clarify the generality of these findings and the overall significance of behavioral context on aggressive behavior in dolphins.