Theses and Dissertations

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Defense Date

1995

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Ocean Science

Department

Oceanographic Center

First Advisor

Keith Ronald

Second Advisor

Naomi Rose

Third Advisor

Richard E. Dodge

Fourth Advisor

Bart Baca

Abstract

Orcas, Orcinus orca, also known as "killer whales," are a species that have been the subject of long-term research. The aim of this study was to quantify percussive behaviors of a population of orcas, identify which individuals in a pod were displaying such behaviors, determine the context in which these behaviors occurred, and offer suggestions to the purpose, if any, that percussive activity may serve in this community.

The study was conducted in Johnstone Strait, British Columbia, Canada during the summer months of 1992-1993. Observations were made during daylight hours. Whales were encountered either opportunistically, or by reports from other whale-watchers and researchers. A total of 542 hours of observational data were collected from 86 individual whales. Behavioral categories were defined as feeding, socializing, traveling, and resting.

The most often observed percussive behaviors were tailslaps; they were therefore analyzed in the greatest detail. The number of tail slaps produced during feeding, socializing, aggregation, directional changes, and in the presence of boats were statistically compared. It has been suggested that calves and juveniles engage in percussive activity as a form of play during socializing, and that percussive behavior may aid in building physical strength and motor training. Adolescents and adults may engage in percussive actions to convey information about a direction change to other animals, strengthen social ties, express sociosexual behavior, and assist in social development, all of which could establish and strengthen social skills and social bonds among other individuals in the community. Other hypotheses for percussive behavior in this community include: forms of aggression; a type of warning signal; incidental occurrences due to elevated activity levels; a form of greeting among individuals; an expression of courtship behavior; a way to establish or re-establish dominant-subordinate relationships; an aid in the capture of prey during feeding; and a type of energy release either before or after resting behavior.

It appears that each age class may have its own agenda for displaying percussive activity, depending on the context in which it was performed. The reason why each individual engages in percussive actions may be multifaceted for various situations, and each reason may not be bound to a particular context. The high level of occurrence of percussive behaviors implies that they are relevant to the daily activities of the northern resident community of orcas that inhabit the region of Johnstone Strait, British Columbia, Canada.

ORCID ID

0000-0001-8719-5629

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