Dissecting the effects of behaviour and habitat on the locomotion of a lizard (Urosaurus ornatus)

Locomotion is one way that organisms interface with their environment, and this relationship can be affected by the structural habitat and behavioural context associated with each movement. Previous studies have examined the effects of habitat or behaviour on locomotion individually, but have not addressed the potential interaction between these factors. In addition, studies often use induced behaviours or manipulated habitats to examine the effects of habitat and behaviour on locomotion. Although valuable, these approaches provide little information on the range of natural behaviours and habitats that animals occupy. To address these issues, we examined the effects of structural habitat, behavioural context, and their interaction on undisturbed locomotor speeds in the ornate tree lizard, Urosaurus ornatus. Detailed video analysis revealed that both habitat and behaviour affect locomotion individually; locomotor speed decreases with increasing perch height when animals move on woody substrates and while displaying and capturing prey. Surprisingly, we found no relationship between speed and perch diameter or substrate incline. Additionally, we show that the interaction between perch diameter and feeding behaviour results in a negative relationship between speed and perch diameter during feeding but not during other behaviours. In light of these findings, we suggest that the relationship between habitat, behaviour and speed is affected by the level of locomotor performance (maximal versus submaximal) that animals routinely use during undisturbed activity.