Population dynamics of three lizard species from the genus Sceloporus: short-term changes in demographic parameters.

Most demographic studies focus on numerical changes that occur within populations across years. However, typically studies at an interannual scale do not provide information on the particular times of the year (particular months or seasons) when rates of survival, recruitment, or migration increase or decrease due to physiological, behavioral or ecological processes. These monthly or seasonal changes in demographic parameters may lead to substantial variations in population abundance. In this study, we collected capture-mark-recapture data on 3 species of lizards of the genus Sceloporus (Sceloporus torquatus, Sceloporus grammicus and Sceloporus megalepidurus) found in ecologically similar habitats to examine potential changes in demographic rates among 3 different climatic seasons: rainy, cold-dry and warm-dry seasons. We tested different hypotheses about the effect of these seasons on survival, recruitment of new adults, and temporary emigration. We found that during the season with severe thermal constraints, the cold-dry season, survival of S. torquatus decreased markedly. We also detected a considerable increase in the recruitment rate of S. grammicus during the rainy season, when these lizards are establishing territories and finding mates. In contrast, we found no evidence of intra-annual changes in the rate of temporary emigration. In addition, we calculated abundance and population growth rates for each species and for each season. Our study represents a significant contribution to the understanding of intra-annual demographic variation in lizards.