Subjective resource value affects aggressive behavior independently of resource-holding-potential and color morphs in male common wall lizard

Abstract

Game theory models predict the outcome of a dyadic contest to depend on opponents’ asymmetries in three main traits: resource-holding potential (RHP), resource value (RV) and aggressiveness. Using male common wall lizards Podarcis muralis, a polymorphic species showing three discrete morphs (white, yellow, and red), we investigated how the aggressive behavior varies according to a change in subjective RV and color morphs, while controlling for the asymmetry in RHP (using mirrors). By comparing the aggression of the same individual towards its mirror image in two different arenas (familiar = high subjective RV; novel = low subjective RV), we showed that lizard aggressive behavior was more intense and prolonged in the familiar arena than in the new one, thus supporting the occurrence of a direct relationship between motivation and aggression in this species. We also found the overall aggressiveness to differ from individual to individual, supporting the general hypothesis that aggressiveness is a trait associated with personality. By contrast, no effect of morphs was detected, ruling out the occurrence of morph specific variation in the aggressiveness. Our results highlight that an individual’s motivation and personality might be as important as RHP and RV in the resolution of animal contests.

Close encounters of the three morphs: Does color affect aggression in a polymorphic lizard?

“…This hypothesis could be tested by inserting the focal lizards in unknown boxes, different from those used for acclimation. Indeed, a previous study with staged contests demonstrated that the motivation of resident individuals for territory defense could be a driving force to the contest outcome (Sacchi et al, 2021), so the aggressive response could be lowered by this condition and the role of color morph underestimated.…”

“…Only six individuals never interacted with the mirror nor entered the half cage near the stimulus. This could be due to stress, fear, or personality since individual responses can differ according to the provided stimulus (static models, regular mirrors, nonreversing mirrors, or real opponents; Li et al, 2018; Sacchi et al, 2021). The comparison of the number of aggressive interactions between pairs of morphs did not reveal any prevalence in attacking a specific morph.…”

Colour variation of the Maltese wall lizards (Podarcis filfolensis) at population and individual levels in the Linosa island

“…Colour of Maltese wall lizards sensibly changed with individual size in both sexes, but with opposite patterns in upper-and under-parts of the body, suggesting the occurrence of ontogenetic variation that promotes increased contrast between dorsal and ventral colourations. Size is one of the first determinant of the outcome of a dyadic contest in lizards (Sacchi et al 2009(Sacchi et al , 2021. Therefore, reliably predicting the size of potential opponents is crucial for males, to avoid engaging in costly and not necessary combats.…”