Date of Award

Spring 2010

Degree Type

Masters Thesis

Degree Name

Master of Arts (MA)

Department

Psychology

Committee Chair

Stan Kuczaj

Committee Chair Department

Psychology

Committee Member 2

Tammy Greer

Committee Member 2 Department

Psychology

Committee Member 3

John Harsh

Committee Member 3 Department

Psychology

Abstract

The current study examined the site fidelity and association patterns of a community of 678 wild bottlenose dolphins (Tursiops truncatus) in the Mississippi Sound (Sound) over a three-year period (May 2004 - April 2007). Using photoidentification techniques, 74% (n = 498) of the identified dolphins were classified as transients, while 10% (n = 71) were classified as year-round residents, and 16% (n = 109) were classified as seasonal residents based on their sighting histories. Thirty-nine "select" dolphins (n = 17 seasonal residents, n = 22 yearround residents) that were sighted five or more times over the study period were used to calculate the coefficients of association (COAs) using the Half-weight index. Non-zero COAs ranged from 0.10 to 0.91 (M = 0.25), with a majority (91 %) falling below 0.40. Select dolphins had an average of 55.6 associates, and 21% of the associations between two dolphins were repeated associations. Social networking analyses were used to investigate the substructure of this network. The network was filtered such that only associations greater than the mean COA were represented, and only individuals with more than one association were included (n = 36). The Girvan-Newman algorithm revealed three distinct communities within the network. A randomized test of autocorrelation provided evidence that the dolphins in this network do not preferentially associate with individuals of the same residency classification. However, individuals of high degree (number and weight of network neighbors) were more likely to associate more closely with other individuals of high degree. As individuals with high measures of centrality (degree and betweenness) were removed from the network, the network began to break apart, but not prior to the removal of several individuals, suggesting the structure of the network is maintained by multiple individuals. Networks created for each of the three barrier islands and the channel revealed distinct differences in social structure at those locations. Network centrality measures were also calculated for a group of dolphins sighted two or more times before and after Hurricane Katrina, to examine its effects on the social structure of dolphins in the Sound. Most of the measures of centrality were significantly higher after the hurricane, suggesting that the dolphins in the network were more strongly connected at this time.

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