TERRITORIAL DEFENSE BY MALE GREEN ANOLES: AN EXPERIMENTAL TEST OF THE ROLES OF RESIDENCY AND RESOURCE QUALITY

To test the hypothesis that males will more vigorously defend high-value territories (those containing females versus those with no females), male green anoles (Anolis carolinensis) were allowed to establish residency in 50 x 25 x 31-cm terraria with or without a female present. Each male was then removed for 1, 3, 5, or 7 h while an intruder was given access to the terrarium. The original owner was then returned to the terrarium with the intruder present, and the aggressive acts of both males were recorded. An aggression index was calculated for each owner-intruder pair to determine which member "won" the contest. Owners won more contests than intruders after all removal times except 7 h. Aggression did not increase significantly at intermediate removal times, when both males may have perceived themselves as territory owners. When the value of a territory was increased by the presence of a female, aggression by both the owner and the intruder increased significantly after the 3-h owner removal time, and aggression by the intruder (but not owner) increased significantly after the 5-h owner removal time. Winners of territorial contests in male green anoles seem to be determined by the resource holding potential of the contestants, the value of a contested territory, and particularly the ability of males to assess each other.