Male Sceloporus tristichus Lizards Increase Aggression in the Presence of a Conspecific Intruder

Territoriality is seen across different species of animals anywhere, from birds, fish, and mammals to reptiles. Although many animals use several types of signals to defend their territories, signals in different sensory modalities have varying properties that may influence their effectiveness in different contexts. This study investigates whether male plateau fence lizards (Sceloporus tristichus) use chemical or visual behavior during territory defense. Both visual and chemical communication modalities inform the audience about the producer’s physiological condition. The results show no obvious tradeoff between visual and chemical modalities in the behavior recorded in the presence of another male lizard compared to when undisturbed, suggesting that these signals are not used in territory defense. An increased visual head bob display is the most common spiny lizard territory defense response to conspecific intruders. However, this is not always the case, as environmental and evolutionary constraints influence communication. This species does not perform typical territorial behavior. However, there was a significant increase in aggressive visual displays, called full shows, in the presence of the intruding live stimulus. An increase in full shows could be a less conspicuous way to defend their territory instead of performing an entire broadcasting head bob display while perched in an open/exposed habitat notably filled with predatory birds. This shows modification within one communication modality to result in more effective communication.