O ne strong pattern to emerge from field studies of behav- ioral interactions between predators and prey is a positive association between prey response and the intensity of the perceived threat (Stankowich and Blumstein 2005).The entire defensive repertoire of a population or a species may have evolved due to the strong and continuously selective pressure wielded by its natural predators (Greene 1988;Vamosi 2005).Moreover, predators might have coevolved to deal with these defensive strategies, generating a predator-prey arms race (e.g., Geffeney et al. 2002).Lizards are frequent prey of frogs, other lizards, snakes, birds, mammals, and even invertebrates (Vitt and Caldwell 2014), and are known to employ a variety of defensive strategies that include toxic and distasteful secretions, cryptic and aposematic coloration, and a variety of defensive postures and behaviors (Greene 1988; Lima 1998; Downes 2001), the most common of which are escape (flight), immobility, and tail-waving (Rand and Marx 1967; Telemeco et al. 2011).Basilisks (Basiliscus spp.) are well known for using a remarkable antipredator behavior that consists of bipedaling across water as readily as on land (Rand and Marx 1967; Hsieh and Lauder 2004).However, diving behavior, another antipredator strategy used by basilisks, is rarely mentioned in the scientific literature (Rand and Marx 1967; Hernández-Córdoba et al. 2012).Herein we describe in detail the diving behavior of the Western Basilisk, Basiliscus galeritus Duméril 1851.Western Basilisks range from the Pacific lowlands and eastern premontane elevations of Panama's Darien region southward through Colombia's Choco biogeographic region, the inter-Andean valleys of the Magdalena and Cauca Rivers, and throughout western Ecuador at elevations from sea level When Running on Water isn't Enough, You Can Dive: Field Observation of Diving Behavior as an Antipredator Strategy in a Western Basilisk, Basiliscus galeritus