Food Availability as a Proximate Factor Influencing Individual Growth Rates in the Iguanid Lizard Sceloporus Merriami

Abstract

Von Bertalanffy, logistic—by—length, and logistic—by—weight models of individual growth for 2 populations of Sceloporus merriami were estimated from 3 yr (1974—1976) of mark—recapture data using nonlinear regression. The logistic—by—weight model was found to provide the best fit to observed growth rates. Abundance of arthropod prey was estimated by 2 techniques and found to be serially correlated with seasonal precipitation. Prey abundance was correlated with annual precipitation. Individual foraging success was found to be correlated with estimated prey abundance. Parameters of logistic—by—weight growth models were compared for the 3 yr of the study and revealed that variation in food availability resulted in predictable variation in individual growth rates. Individual growth rates were positively correlated with active—season and annual precipitation and with estimates of food availability. The limitations of using stationary growth models to describe a potentially nonstationary process such as individual growth are discussed.