A multi-index approach to assessing foraging mode: a case study using chameleons.

Abstract

Classifying the foraging mode of a species is challenging and is usually assessed through movement-based indices. Without considering what motivates movement, these indices may result in a biased interpretation of foraging mode-overlooking the fact that movement is influenced by multiple biological factors and not solely foraging. Conversely, while attack-based indices provide a more informative assessment of foraging mode because behavior is incorporated, the most comprehensive and reliable assessments should incorporate both movement- and attack-based indices. We applied a combination of movement- and attack-based indices to reevaluate foraging mode in chameleons, using Bradypodion pumilum as a case study. Focal observations were used to record the behaviors of 38 individuals, 12 of which were telemetered over two 10-day periods. Chameleons spent most of the day in stationary positions, perched in direct sunlight during mornings but in partial sunlight or shaded areas during afternoons. From >100 feeding events, chameleons had a significantly higher percentage of attacks and rate of attacks on prey while stationary than when moving. Most recorded intraspecific interactions were between females and males. Not only do our findings suggest that chameleons are motivated to move for several reasons but after considering life history traits in conjunction with our findings, we propose a paradigm shift in chameleon foraging mode suggesting that they should be considered ambush foragers instead of "cruise foragers" as previously classified. Overall, our findings demonstrate the importance of a multifaceted approach to foraging mode assessments, and we caution against using only one type of index in evaluations.