Throat Color Polymorphism is Related to Differences in Aggression in Aegean Wall Lizards

Aggressive behavior can be used to establish and maintain access to crucial resources such as space, food, and mating opportunities. Color polymorphic animals sometimes exhibit morph-correlated aggressive behaviors that can influence relative reproductive success and, thus, the maintenance of polymorphism. Aegean wall lizards, Podarcis erhardii, exhibit one of three monochromatic throat color morphs: orange, white, and yellow. Previously, male P. erhardii color morphs were shown to differ in their use of aggressive behaviors and ability to win staged contests during laboratory experiments. However, whether these color morphs use aggressive behavior differently in their natural setting where ecological and environmental factors are not standardized remains unknown. Here, we observed interactions of wall lizards over a large section of dry stone wall to investigate behavioral differences in aggression among color morphs in situ. We compared the counts and intensities (aggression scores) of aggressive behaviors (both performing and receiving aggression) and found that color morphs differ significantly in the frequencies and intensities of their aggressive behaviors. White morphs exhibited significantly more aggression than orange and yellow morphs on dry stone walls. Taken together, results from in situ and ex situ behavioral studies suggest that the smaller, more common white color morphs are more aggressive, which may help explain their relatively greater abundance and persistence across the species' range.