Analysis of aggressive behaviour in the bluegill sunfish Lepomis macrochirus rafinesque: Effects of sex and size

• Published in: Animal behaviour Vol. 25; pp. 122 - 130
• Main Authors: Henderson, David L., Chiszar, David A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.1977
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1016/0003-3472(77)90074-4

Two experiments explored the effects of resident and intruder sex (experiment 1) and size (experiment 2) upon aggressive behaviour exhibited by sunfish during 30-min observation sessions. Bluegill sunfish ( Lepomis macrpchirus Rafinesque) in non-reproductive condition were subjects in both experiments. Residents occupied 95-litre aquaria for 7 days prior to the introduction of an intruder at the start of an observation session. This paradigm allows independent assessment of the effects of both resident-aggressor sex (or size) and intruder-aggressee sex (or size). The first experiment revealed that neither resident sex nor intruder sex exerted significant effects on resident aggressiveness. Experiment 2 showed that large residents exhibited more aggressive responses to both large and small intruders than did small residents. Implications of these findings for perceptual mechanisms underlying the release of bluegill aggression are discussed.