Growth effort of Sceloporus scalaris (Sauria: Phrynosomatidae) at La Michilía Biosphere Reserve, Mexico

Using Mark-Recapture methods the growth effort of Sceloporus scalaris was studied at La Michilìa Biosphere Reserve, Durango, Mexico. A total of 146 recaptures on 68 individuals were obtained over four years on a 50 000 m 2 transect. To calculate the growth rate of Sceloporus scalaris individuals, we analyzed the data from two sources. The first using the recapture records of the same individuals over different seasons and the second using the records of cohorts during different periods. The growth effort of S. scalaris drastically diminishes as the organism grows. The growth rate of males and females is about equal for individuals from both clutches. In adults, where it is possible to compare among seasons, we measure quicker growth during the spring. The growth pattern of S. scalaris at La Michilìa follows the predictions proposed by the Bertalanffy model. Maximum growth rates are in the younger age classes and these rates decrease as size increases. The growing period of S. scalaris is correlated with the seasons at La Michilìa Biosphere Reserve. Newborn S. scalaris appear when the availability of nourishment is still the most propitious for growth at faster rates. Such adaptations to the environment determine many key population attributes of this species in this zone. The sexual maturity age of S. scalaris is very early at La Michilìa, only 4.5 to 6 months. Undoubtedly, the growth pattern of S. scalaris at La Michilìa Biosphere Reserve can help explain the structure and dynamics of this population. Usando métodos de Marca-Recaptura estudiamos el esfuerzo de crecimiento de Sceloporus scalaris en la Reserva de la Biosfera de La Michilìa, Durango, México. Se analizaron 146 registros de recaptura sobre 68 individuos en cuatro a os de estudio en un transecto de 50 000 m2. El esfuerzo de crecimiento disminuye drasticamente conforme el individuo crece, es casi igual para los machos y hembras de las dos puestas, y en el caso de los adultos se registró un crecimiento más rápido en primavera. El patrón de crecimiento sigue las predicciones propuestas por el modelo de Bertalanffy. Los recién nacidos de S. scalaris eclosionan cuando la disponibilidad de alimento es todavìa la m·s propicia. La madurez sexual de los individuos es muy precoz en La Michilía: de 4.5 a 6 meses. El patrón de crecimiento de S. scalaris en La Michilía ayuda a explicar la estructura y dinámica de esta población.