The choice of arboreal escape paths and its consequences for the locomotor behaviour of four species of Anolis lizards

Abstract

The direction and speed of escape locomotion can affect the ability of an animal to evade a predator, and variation in habitat structure often affects speed. Consequently, the escape paths chosen by animals may affect their performance and subsequent survival. Arboreal locomotion is well suited for gaining insight into the choice of escape routes because of the discrete paths formed by branches. Decreased branch diameter and increased angles between branches can significantly decrease locomotor speeds, but no previous study has determined whether arboreal lizards selectively choose alternative paths. We quantified choice of escape paths and locomotor performance of four syntopic species of arboreal Anolis lizards in their natural habitat and in the laboratory. In the field, species with shorter limbs occurred more commonly on narrow perches than did long-limbed species, but all species favoured escape paths with larger-diameter perches and straighter interperch angles. Thus, short-limbed species used narrower perches than long-limbed species merely as a result of what they encountered, rather than as a result of a biased choice at branching points. In natural vegetation, choosing branches with the largest diameter often results in the straightest path. However, in the laboratory, most lizards preferred large-diameter perches with a sharp turn to continuing a straight path onto a small-diameter perch. Although an overriding preference for larger perch diameter may optimize escape speed within a single perch, a maladaptive side-effect could be a compromise of the overall rate of gaining distance from starting points in paths with turns.