RELATIONSHIPS AMONG FORAGING VARIABLES, PHYLOGENY, AND FORAGING MODES, WITH NEW DATA FOR NINE NORTH AMERICAN LIZARD SPECIES

Abstract

Complete characterization of lizard foraging behaviors may require information about aspects rarely measured. Most studies record only number of movements per minute (MPM) and/or percent of time moving (PTM), but lizards differ markedly in average speed (AS) and speed while moving (MS) during foraging and in proportion of attacks initiated after detecting prey while the lizard is moving (PAM). We present data on these variables for nine lizard species and on foraging speed for several others, permitting first assessments of relationships between speed, PAM, and both phylogeny and foraging mode; examination of the effect of body length on foraging speed; and correlative analyses of relationships between foraging variables. Although sprint speed may increase with body size, foraging speed did not, presumably for two reasons. Because search speed is much lower than sprint speed, as is speed of movement between ambush sites, searching efficiency and stamina may be more important determinants of foraging speed than is sprint speed. Second, the body size range was small, allowing the possibility that foraging speed may vary with body length over the much larger size range between the smallest and largest species worldwide. Nevertheless, a large majority of lizard species are in the size range tested, suggesting that body length may not strongly affect foraging speed except when extremely short or long species are included in comparative analyses. High PAM, high AS, and low MS were characteristic of autarchoglossans and active foragers, whereas low PAM, low AS and high MS were exhibited by iguanians and ambush foragers. In independent species analyses, significant correlations were observed between several pairs of foraging variables. In analyses using phylogenetically independent contrasts, the only significant finding was a strong positive correlation between PAM and PTM. Although these findings suggest that foraging speed, MPM, and either PTM or PAM may provide independent measures of foraging activity needed to adequately describe interspecific variation, this conclusion is tentative due to the small sample size of limited taxonomic breadth.