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Environmental temperatures influence ectotherms’ physiology and capacity to perform activities necessary for survival and reproduction. Time available to perform those activities is determined by thermal tolerances and environmental temperatures. Estimates of activity time might enhance our ability to predict suitable areas for species’ persistence in face of climate warming, compared to the exclusive use of environmental temperatures, without considering thermal tolerances. We compare the ability of environmental temperatures and estimates of activity time to predict the geographic distribution of a tropical lizard, Tropidurus torquatus. We compared 105 estimates of activity time, resulting from the combination of four methodological decisions: 1) how to estimate daily environmental temperature variation (modeling a sinusoid wave ranging from monthly minimum to maximum temperature, extrapolating from operative temperatures measured in field or using biophysical projections of microclimate)? 2) In which temperature range are animals considered active? 3) Should these ranges be determined from body temperatures obtained in laboratory or in field? And 4) should thermoregulation simulations be included in estimations? We show that models using estimates of activity time made with the sinusoid and biophysical methods had higher predictive accuracy than those using environmental temperatures alone. Estimates made using the central 90% of temperatures measured in a thermal gradient as the temperature range for activity also ranked higher than environmental temperatures. Thermoregulation simulations did not improve model accuracy. Precipitation ranked higher than thermally related predictors. Activity time adds important information to distribution modeling and should be considered as a predictor in studies of the distribution of ectotherms. The distribution of T. torquatus is restricted by precipitation and by the effect of lower temperatures on their time of activity and climate warming could lead to range expansion. We provide an R package ‘Mapinguari’ with tools to generate spatial predictors based on the processes described herein.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Society for the Study of Amphibians and Reptiles is collaborating with JSTOR to digitize, preserve and extend access to Journal of Herpetology. ABSTRACT.-We studied the reproductive cycle of Tropidurus torquatus in the Cerrado biome of central Brazil from October 1997 to September 1998. Females reached sexual maturity at about 65 mm snout-vent length (SVL), whereas males became sexually mature at 70 mm SVL. Females were reproductively active between August and February, although males contained spermatozoa in the epididymides year-round. Frequency of reproductive females was inversely correlated with precipitation and air humidity and positively correlated with day length. Reproductive activity of males was inversely correlated with air humidity and positively correlated with day length. Females laid six eggs on average and may have produced up to three clutches per reproductive season. With the advancement of the reproductive season, clutches tended to be smaller, whereas egg size remained constant Fat body mass varied inversely with reproductive activity in both sexes, but females had significantly larger values than males. After an incubation period of approximately 5 months, young emerged at a SVL around 31 mm. Juveniles began to accumulate energy in fat bodies after reaching 47 mm SVL. The fat body cycle and the recruitment pattern of T. torquatus suggest that food resources are not limiting and that the length of the reproductive season is most likely constrained by the availability of microhabitats suitable for egg development.

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