Biology Ph.D. Dissertations

Underlying Mechanisms That Affect Crayfish Agonistic Interactions and Resource Acquisition

Date of Award

2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biological Sciences

First Advisor

Paul Moore

Abstract

Animals engage in agonistic bouts that result in the development of dominance relationships. The development of a dominant status infers increased access to valuable resources. There are several underlying mechanisms that can alter behavior during agonistic interactions and consequently alter the outcome of those interactions. Extrinsic factors such as chemical communication, shelter residency, conspecifics, and mates; and intrinsic factors such as physical size, sex, and reproductive state are many of the important influences that can alter aggression and outcomes during interactions. This dissertation contains field and laboratory research that analyze how these factors influence agonistic interactions and the impact these interactions have on the development of dominance relationships and resource use. The influence of shelter residency and shelter preference on agonistic interactions was found to be important in populations of size matched individuals. In naturally occurring systems the outcome of agonistic interactions were not impacted by shelter residency, but by size. This research indicates the importance for understanding shelter availability, abundance, and quality in different natural systems to develop a clearer understanding that the impact of shelter use and preference have on dominance relationships. Animals were also shown to exhibit different social behaviors during interactions. Dominant males generate currents and release urine differently than subordinates. Research has shown that urine is an important signal released during agonistic interactions. Crayfish have the ability to control and alter a conspecifics behavior by modifying its transfer of chemical signals during bouts. Male and female crayfish also engage one another in natural systems and make the choice to engage in agonistic bouts or mating behavior. Females are more likely to win an encounter with a male if the male is in non-reproductive form. Animals were shown to only exhibit mating behavior when both males and females were reproductive. Animals communicate during interactions and compete for both resources and mates that are essential for increasing an individual’s fitness. Research on the underlying mechanisms that influence motivation can provide a clearer understanding of how to manipulate and alter aggression and the dominance relationships that are so prevalent in many animal systems.

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