Physical and chemical Variables promote successsful nesting in high mountain Sceloporus lizards in central México

Abstract

Sceloporus (S. aenus and S. scalaris) are oviparous sibling lizard species inhabiting high mountain zones (.2700 m) in central México. Females of these species lay their eggs in soil mounds left by burrowing gophers (Pappogeomys). Numerous abiotic factors can affect site selection and subsequent development of the lizard embryos, but little is known of the relationship between the optimal physical and chemical variables of the surrounding soil that allow development and successful hatching of the eggs, especially in high-elevation environments. We hypothesized that soil parameters and temperature drive site selections by females seeking nest locations favorable to embryonic development. We recorded differences in the abiotic parameters of soil mounds between dry and rainy seasons, irrespective of whether the mounds contained eggs. Statistical analyses revealed that an environment of high relative humidity and stable temperatures necessary for mound selection as a nesting site were associated with intermediate moisture content, high organic matter content, high values of cation exchange capacity, and relatively high porosity of the soil substrate. Collectively, these values of abiotic soil traits prevent sudden changes in temperature and humidityat the nest depth, providing conditions that promote successful development and hatching. Understanding the relative importance of these abiotic factors in nest site selection by Sceloporus should contribute to an understanding of the adaptations of oviparous reptiles that reproduce in different environments.