Grace Otto

Date of Award

2014

Document Type

Thesis

Degree Name

Bachelors

Department

Social Sciences

First Advisor

Bauer, Gordon

Keywords

Threespot Damselfish, Stegastes planifrons, Fish, Agression, Animal Behavior

Area of Concentration

Psychology

Abstract

Many members of the Pomacentridae family, commonly referred to as damselfish, are herbivorous, consuming algae regularly as part of their diet, and territorial, aggressively defending where they feed and reproduce. These characteristics affect coexisting species and the physical reef, making damselfish behavior an important component of coral reef ecosystems. The purpose of this study is to analyze how the familiarity of other fish that enter damselfish territories, called intruders, may affect the variation of aggressive behaviors of threespot damselfish (Stegastes planifrons). In an observational study (Study 1), threespot damselfish on the reef were observed and intruding species and aggressive behaviors toward them were analyzed. Then, in an experimental study (Study 2), subjects were exposed to rare or frequent novel objects, colored plates meant to represent fish, that were shown close to or far from the territories. By recording intruding species and territory holders’ behavior toward these species, the effects of frequency of those species on damselfish behavior were analyzed. The effects of frequency and proximity of novel objects were also analyzed. In Study 1, attacks were more frequent on fish showing greater frequency. These results show that familiarity with intruders affects aggressive behavior toward intruders in threespot damselfish in the wild. In Study 2, most plates were not attacked during presentation and those that were received low numbers of attacks. These results suggest that damselfish aggression is affected differently by fish and novel objects. The low number of attacks could be explained by the salience of the plates in the wild and by differences in behavior between wild and captive damselfish.

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