TEMPORAL AND SPATIAL VARIATION IN INDIVIDUAL GROWTH IN THE SPINY LIZARD, SCELOPORUS-JARROVI

Temporal and spatial variation in individual growth rates of Sceloporus jarrovi from three populations in the Chiricahua Mountains of southeastern Arizona were studied from 1973 to 1976. Annual variation in individual growth rate was observed only in the low-altitude population. Growth rates for individuals in the low-altitude population were lowest in 1974 (a year in which a drought occurred; 0.06 mm d(-1)), and yearlings in the low-altitude population had particularly low growth rates in 1974 relative to other years. Averaging over all years, two high-altitude populations (0.16 mm d(-1) in both populations) had significantly higher growth rates than the low-altitude population (0.12 mm d(-1)). Data on arthropod abundance and rainfall suggest that food availability can explain much of the observed temporal and spatial variation in individual growth rates.