Masters Theses

Date of Award

5-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

Neil Greenberg

Committee Members

Gordon M. Burghardt, Arthur C. Echternacht

Abstract

The establishment of a social dominance relationship is known to involve many behavioral changes in its participants. This study was conducted to document the effects of such a relationship on the behavioral patterns of Anolis carolinensis males, as well as to examine the nature of the dominance relationship itself. To do this, 13 lizards forming 9 pairs were placed in testing chambers composed of three distinct compartments through which the animals could move freely. In addition to being tested as members of a dominant-subordinate pair, animals were also observed when they were alone in the cages in order to determine a baseline for all the behaviors that were studied. Observations of animals that were in the same compartment with their partner were made separately from those when the animals were in separate compartments and contrasted with each individual's patterns when isolated. Lizards that did the most patrolling as isolates consistently defeated animals that patrolled less. Males that became dominants showed an increase in patrolling while those that became subordinates showed a decrease. Both dominants and subordinates were found to be less active in the presence of their partners than when they were alone. Subordinates were considerably more active when the dominant males were absent than when they were present. Compared to baseline levels, subordinates showed more submissive postures and lower site selections, but only when they were in the presence of dominants. Subordinates were darker in color when dominants were present than when they were absent. In both cases they were darker than they had been as isolates. Dominant males tended to enter occupied compartments at higher than expected rates, while subordinates actively avoided entering occupied compartments. Subordinates also avoided spending time in the center compartment of the testing chamber but dominants divided their time relatively equally among the three. The results of this experiment hinted at several things. First, the fact that dominants show fewer changes from baseline levels than subordinates do suggests that their behavior is closer to "normal" for A. carolinensis than is the case with subordinates. Second, many of the behavioral changes that subordinates display are manifested only when dominants are absent or are different from the changes that occur when dominants are present. Subordinate males are flexible in their responses to social subordination and are capable of responding rapidly to the absences of dominants. Third, subordinates will actively try to avoid dominants if given the opportunity. Dominants, however, tend to seek out their partners and make no effort to avoid subordinates. Since the testing chambers were relatively small, subordinates could not escape the presence of the other males and were forced to alter their behaviors in order to coexist with the dominant males. This study indicates that the behavioral changes seen in dominants and subordinates are not due simply to pre-existing individual differences, but rather that they are largely dependent upon the specific roles that the animals have within their social dominance relationship.

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