Interspecific Aggression in a Hawaiian Pomacentrid: Stegastes Fasciolatus
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Field observations were made on interspecific aggression in the Hawaiian pomacentrid, Stegastes fasciolatus. Included are 17 species of intruders of which 3 are herbivores, 8 are carnivores, and 6 are omnivores. For purposes of the investigation, the resident's territory was divided into three horizontal and two vertical components. When an intruder entered a territory, the position of the intruder was recorded along with whether or not the intruder was chased. Totals were obtained for each species and converted to a three dimensional matrix. Various loglinear models were applied to the matrix to determine the relative significance of each term. It was determined that the species of intruder, along with its feeding habits, was the most important factor in eliciting an aggressive response from the resident.. The horizontal distance from the algal mat was found to be more important when the intruder was in close proximity to the substrate and not as important when distant. Finally, it was determined that different species violate a territory in different ways, but it is a reflection of the behavior shown by the resident towards them. The ecological justifications of such behaviors are discussed.