Herpetological Conservation and Biology 10(2):661–665. Submitted: 24 December 2014; Accepted: 17 June 2015; Published: 31 August 2015. Copyright © 2015. Thiago Maia-Carneiro 661 All Rights Reserved FLIGHT INITIATION DISTANCES OF TROPIDURUS HISPIDUS AND TROPIDURUS SEMITAENIATUS (SQUAMATA, TROPIDURIDAE) IN SYMPATRY THIAGO MAIA-CARNEIRO 1 AND CARLOS FREDRICO D. ROCHA Departamento de Ecologia, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, CEP 20550‒013, Rio de Janeiro, Brazil 1 Corresponding author, e-mail: tmaiacarneiro@gmail.com Abstract.—Flight initiation distance (FID) is the minimum approach distance allowed for a potential predator before an animal starts a locomotor escape. Factors such as body size and body temperature might affect this behavior in lizards. Here, we analyzed the influences of these factors on defensive behaviors of sympatric lizards Tropidurus hispidus and T. semitaeniatus on rock outcrops in northeastern Brazil. All individuals of the two species employed locomotor escape. Shorter FID for T. semitaeniatus in comparison with T. hispidus suggested that the former rely more on immobility to conceal their presence and/or that it is more effective at evading predators. Furthermore, Tropidurus hispidus lizards might be faster than T. semitaeniatus and because of that, individuals may take flight early at low velocities and retain the capacity to increase their velocity when necessary. Inter-specific differences in body dimensions apparently represented important influences for this defensive behavior. Neither SVL nor body mass were important factors influencing intra- specific variations in FID. At low body temperatures, T. hispidus tended to exhibit greater FID, presumably due to impaired locomotor capacity. Key Words.—anti-predator behavior; approach distance; defense behavior; defensive mechanisms; escape behavior INTRODUCTION Lizard prey may permit a minimum approach distance for a predator before starting a locomotor escape for capture avoidance, which is the flight initiation distance (FID; Ydenberg and Dill 1986; Cooper and Frederick 2007), and body size, body temperature, and differences in escape efficiency might influence this behavior. For instance, in North America, Callisaurus draconoides had lower FID compared to Cophosaurus texanus possibly due to its greater body dimensions that make it more visible to predators and/or to differential energetic constraints (Bulova 1994). In Brazil, Tropidurus oreadicus with low body temperatures had longer FID than individuals with higher body temperatures (Rocha and Bergallo 1990). For related sympatric species co- occurring locally, escape decisions might be qualitatively similar due to relatedness, and divergences in defense responses (e.g., in FID) might arise from inter-specific ecological differences that affect prediction of risk (Cooper and Avalos 2010). The lizards Tropidurus hispidus and Tropidurus semitaeniatus (Squamata, Tropiduridae) often occur in sympatry on rock outcrops in northeastern Brazil. Tropidurus hispidus occurs in several ecoregions along its broad geographic distribution range in South America, inhabiting Amazonian savannas, Atlantic Forest, Cerrado, and Caatinga (Rodrigues 1987, 1988; Avila‒Pires 1995; Carvalho 2013). Tropidurus semitaeniatus occurs in Caatinga, Cerrado boundaries, and in zones towards the Atlantic Forest, where it is found primarily on rock outcrops (Carvalho 2013). Morphological differences exist between T. hispidus and T. semitaeniatus: individuals of the former species are bulkier and achieve larger body sizes, whereas the latter are flattened and smaller, allowing them to take refuge in relatively narrow crevices (Vitt 1981, 1993; Vitt and Goldberg 1983, but see Vitt et al. 1997). In this context, one would expect the occurrence of inter- specific differences in FID influenced by differences in body dimensions. Here, we investigate influences of body size (snout-vent length and body mass) and body temperature on FID exhibited by T. hispidus and T. semitaeniatus lizards, considering possible inter and intra-specific variations. We hypothesized that lizards that are more visible should run earlier in face of a potential predator and that low body temperatures may result in longer FID. Otherwise, larger lizards could have shorter FID due to greater ability to escape in high speeds. MATERIALS AND METHODS Study area.—We collected data in rock outcrop areas in Igatu, in the municipality of Andaraí, state of Bahia, northeastern Brazil (12°53ꞌS, 41°19ꞌW), in the surroundings of the Parque Nacional da Chapada Diamantina. Overall, due to particular altitudinal