The Effects of Intruder Size on the Territoriality of the Threespot Damselfish (Stegastes planifrons)

The Threespot Damselfish, Stegastes planifrons, defends a variable territory size depending upon the level of threat posed by the species encroaching upon it. Aggression patterns in the Threespot Damselfish were studied in relation to intruder size, attack duration, maximum distance of attack and intruder species on a reef in Bonaire, Netherland Antilles. Thirteen species were found to intrude upon Threespot Damselfish territories with the Bicolor Damselfish (Stegastes partitus) being the most frequent visitor (37.8%) followed by the Brown Chromis (Chromis multilineata; 20.2%), Blue Tang (Acanthurus coeruleus; 15.1%) and the Stoplight Parrotfish (Sparisoma viride; 9.2%). Analysis showed a positive correlation between intruder size and attack duration as well as maximum distance traveled by the Threespot Damselfish in pursuit of the intruder during the attack. Data supported the hypothesis that the Threespot Damselfish alters its behavior based on intruder size. Data, however, did not support a species specific relationship between the Threespot Damselfish aggression patterns and the variables selected.

This student research was retrieved from Physis: Journal of Marine Science III (Spring 2008)19: 7-12 from CIEE Bonaire.

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