Density-Dependent Processes during the Juvenile Stage in the Lizard Sceloporus virgatus

We manipulated hatchling cohort density in the Striped Plateau Lizard (Sceloporus virgatus) to investigate density dependence within the juvenile stage of the life cycle. Large-scale field enclosures (800 m2) constructed of drift fencing with pitfall traps for monitoring dispersal were established in the preferred habitat of S. virgatus and treated with high (60) and low (20) densities of hatchlings. Enclosures were monitored over a 10-month period from August 1997 to May 1998 and replicated from August 1998 to May 1999. We found that per capita survivorship, individual growth rates, yearling body lengths, and the proportion of yearlings attaining reproductive maturity were negatively affected by cohort density. Conversely, there was a positive relationship between juvenile dispersal rates and cohort density. These results indicate that density has a significant influence during the juvenile stage of the life cycle and potentially plays a key role in the life-history strategy and population dynamics of S. virgatus.