Right or left-handed: are locomotion type, body size, and microhabitat related to forelimb laterality in anurans?

Laterality, the tendency of animals to use the structures on one side of the body more frequently or efficiently than the other side, can reflect the evolutionary history of species, their ecological characteristics, and cognitive abilities. Using anurans as a model system, it has been hypothesized that the strength of laterality (measured as the percentage of right-handed individuals) is higher in terrestrial and arboreal species, which exhibit asynchronous locomotion type (e.g., walking, climbing), than in aquatic species where synchronous locomotion type (e.g., swimming) predominates. We tested these predictions, including body size as an additional factor, in 19 Neotropical anuran species. For this, we obtained data on forelimb use preference for individuals of such species. We then combined these data with published data for another 14 anuran species obtained through a systematic review of the literature. The combined dataset was used to perform a phylogenetic comparative analysis to verify the strength of laterality in the species. We found that four out of the 19 tested species show a percentage of right-handed individuals that was higher or lower than expected by chance. Individuals of these four species exhibit asynchronous movements of forelimbs during displacements, foraging behaviors, sexual displays, or agonistic interactions. Results of a phyloANOVA and a phyloANCOVA indicated that the strength of laterality was higher in species with asynchronous movements, but this was unrelated to microhabitat and body size. Asynchronous (i.e., non-simultaneous) movements of limbs imply alternating muscle contractions and a higher neural asymmetry than synchronous (i.e., simultaneous) movements of limbs. Therefore, species with an asynchronous locomotion type could be reflecting such complexity and neural asymmetry in higher levels of forelimb laterality. Our results mostly support the predictions based on models that cover the expected relationship between the strength of laterality and the evolutionary ecology of vertebrates.