Short-term movement is different in two syntopic Tropidurus (Squamata, Tropiduridae) species in a semiarid habitat

Abstract

ABSTRACT Displacement occurs during the movement of an organism and can be defined as a change in spatial position, being influenced by biotic and abiotic factors. Measuring the displacement of organisms within their home range is relevant for understanding their use of space and can reveal possible causes and consequences of their movements. During part of the dry season in a semi-arid region of Northeastern Brazil, we marked and observed syntopic Tropidurus hispidus and Tropidurus semitaeniatus individuals in a rocky habitat, and compared their locomotive parameters. We also evaluated the existence of relationships between locomotion and morphometry (snout–vent length and body mass) and abiotic factors (air temperature and relative humidity) of these species. A total of 25.33 hours of observations showed that T. semitaeniatus is clearly less sedentary in relation to T. hispidus, in terms of short-term movements. There was a tendency of smaller individuals to perform a greater number of displacement movements per minute, and displacement distance per minute increased in accordance with an increase in relative humidity for T. semitaeniatus. The movement pattern of the less sedentary T. semitaeniatus may reflect their greater dependence on rocky outcrops and, consequently, they demonstrate better morphological and behavioural adaptations. The surface area–volume relationship, which influences thermoregulatory behaviour, may explain the relationship between morphology and displacement distance in T. semitaeniatus. Furthermore, this species appears to control their movements with the aim of avoiding dehydration caused by restrictions of relative low humidity in their microhabitats. This study has important implications for future research on biomechanics, ecophysiology and modelling of the potential distribution of Tropiduridae lizards under climate change.