Incubation Temperature and Sex Ratio of the Veiled Chameleon (Chamaeleo calyptratus)

—Eggs from five clutches of Chamaeleo calyptratus were incubated at 25, 28, and 308C during the period of sex determination. Sex ratios were slightly biased toward females at all temperatures but did not differ statistically from the expected 1:1 ratio of males and females. Egg survival was sufficiently high that sexbiased temperature-induced mortality cannot account for the lack of departure from 1:1 sex ratios. I conclude that the veiled chameleon has genetic sex determination (GSD) and that anecdotal accounts of temperaturedependent sex determination (TSD) for this species, and other chameleons are likely to reflect reporting or statistical bias. For crocodilians, tuatara, some turtles, and some lizards, temperatures experienced by embryos during incubation affect their sex (Janzen and Paukstis, 1991; Valenzuela and Lance, 2004). For lizards, temperaturedependent sex determination (TSD) is well documented for some species of agamids, scincids and gekkotans (Harlow, 2004). TSD may occur in other families of lizards as well, but reports to date are anecdotal (Harlow, 2004). The problem is that temperaturerelated sex-ratio bias occurs for reasons other than TSD (Valenzuela et al., 2003). For example, temperatureinduced sex-biased mortality during incubation could incorrectly give the appearance of TSD. Reports of TSD could also be statistical artifacts: by chance alone a small number of temperature-biased sex ratios will occur. These apparent sex ratio anomalies (for a GSD species) would be more likely to be noticed and reported than sex ratios not differing from the expected 1:1 ratio of females and males. The family Chamaeleonidae is one of the taxa for which TSD has been suggested on the basis of anecdotal accounts (Harlow, 2004). The objective of this paper is to report results of incubation experiments on the veiled chameleon Chamaeleo calyptratus. Although the study was conducted for purposes other than assessing TSD (unpubl.), results pertinent to TSD are reported here because they (1) document convincingly that incubation temperature does not affect sex SHORTER COMMUNICATIONS 515