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Territory Holders Are More Aggressive Towards Older, More Dangerous Floaters, Walter H. Piper, Katherine R. Lee, Brian Hoover

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Animals that show aggression often risk injury and incur steep energetic costs. Thus, aggression should occur at such times and towards such opponents as to maximize fitness. We tested hypotheses predicting adaptive territorial aggression in the common loon, a species in which ease of observation of territory owners and floaters (prebreeders) seeking to evict them provide a rare window onto owner-floater competition. As predicted, older, more competitive floaters (4-year-olds and upwards) tended to intrude into territories that had produced chicks the previous year (and, hence, were of high quality). Older floaters also showed predicted increases in aggression and territorial yodeling, …