Intra- and interspecific aggressive interactions of Anolis acutus Hallowell, 1856 on St. Croix, U.S. Virgin Islands, with a review of Anolis jaw-locking

Abstract

During a study of endemic Anolis acutus (Hallowell, 1956) on St. Croix, we serendipitously observed intraspecific jaw-locking and interspecific combat with the endangered St. Croix Ground Lizard, Pholidoscelis polops (Cope, 1862). Jaw-locking is an extreme form of aggression in Anolis lizards, in which two males bite each other's snouts. To put our observation of jaw-locking in A. acutus into context, we reviewed the occurrence of this behaviour across Anolis species. Our analysis suggests that jaw-locking primarily occurs in trunk-ground and trunk-crown ecomorphs, indicating that it may occur more frequently in species with distinct ecological adaptations from specific habitats. We also found that Anolis species engaging in jaw-locking have greater sexual size dimorphism (SSD) than anoles overall and that these species are mostly found on islands. The connection between habitat, SSD, and intensity of territoriality we report supports previous studies on Anolis evolution. Furthermore, our record of interspecific combat between A. acutus and P. polops is the first report of this interaction and represents the only record of interfamilial lizard aggression that we found in the literature.