Ecology of Growth of the High Altitude Lizard \u3ci\u3eSceloporus grammicus\u3c/i\u3e on the Eastern Slope of Iztaccihuatl Volcano, Puebla, México

Growth in the lizard Sceloporus grammicus living at two altitudes on the Iztaccihuatl Volcano, Puebla, Mexico, was studied from November 1984 to January 1992. Despite differences in the environmental conditions at these two elevations, individual lizards grew at similar rates at both study sites. Females in both populations grew slower and attained asymptotic size earlier in life than males (0.0025 mm per day and 49.7 mm snout-vent length for females vs. 0.0027 mm per day and 53.2 mm snout-vent length for males). Maximum growth rates were observed early in life in both sexes and sites. Growth in Sceloporus grammicus fits the von Bertalanffy growth model from 0 to 1.5 yrs. of age. Initial growth rates were between 0.10 and 0.15 mm per day in both sexes and sites. Rates decreased to less than 0.02 mm per day at maturity at both sites. Differential investment in feeding activities, social interactions and thermoregulation, differences in the number of predators and competitors, and absence of a hibernation period at both study sites are possible explanations for similar growth rates at both sites