Ecomorphological variation in foraging behaviour by Puerto Rican Anolis lizards

Abstract

Ecomorphs of Anolis lizards evolved convergently via niche partitioning in separate radiations. Each ecomorph has a suite of traits including body size, morphology, microhabitat, anti-predatory behaviour, and foraging, but foraging movements of ecomorphs have not been characterized quantitatively. Data are presented on aspects of foraging for seven species representing four ecomorphs in the cristatellus series from Puerto Rico. Using these and published data for Jamaican and Hispaniolan anoles, an examination is made of predictions based on definitions of ecomorphs by Williams (1972, 1983). Grass-bush and trunk-crown anoles exhibited higher movement rates than trunk-ground anoles. Data for other radiations agree and support a prediction of relatively high movement rates for twig and trunk ecomorphs. All the species studied were ambush foragers and all used the head-down survey posture, indicating phylogenetic stability of these traits. Arboreal species adopted survey posture in about 75% of observations, and grass-bush species used it when on elevated perches. Rates of foraging movements increased as perch height decreased in grass-bush ecomorphs owing to visual obstruction by vegetation limiting the scanning area close to the ground. A similar relationship occurred unexpectedly in a trunk-crown II species, A. stratulus, whereas movement increased marginally with perch height in a trunk-crown I species, A. evermanni. Perch height and movement rates were unrelated in three trunk-ground species. Movements per minute and per cent time moving were highly correlated among species owing to the brevity of individual movements. Data from other Greater Antillean radiations are needed to separate the effects of ecology and phylogeny on anole foraging.