Demography of the Fence Lizard, Sceloporus undulatus, in Northern Mississippi

A population of the northern fence lizard Sceloporus undulatus was studied for four years along a riverine pine bluff in northern Mississippi for comparison with previous studies and to identify factors influencing mortality rates and annual variations in reproduction, growth, survival, and population densities. Reproductive parameters were similar to those of other eastern woodland populations, with clutch size averaging 9.4. Most males and females were reproductive by age one year. Age ratios were 1:1 between yearlings and older adults; sex ratios favored females more in older age groups and resulted from higher mortality rates in males. Annual survivorship averaged 30% for yearlings and adults and showed a loose inverse correlation with injury rates (broken tails) on different vegetational zones of the study area. Spring population densities were among the highest reported for this species, at up to 72 (717 g)/ha. Tree trunks (mostly pines) were perch sites >70% of the time. Females used larger diameter oak trees more than did males, possibly reducing injury rates and enhancing survivorship. Growth, volume of food in stomachs, reproduction, and survival seemed little affected by variations in precipitation between two years; rather, population fluctuations seemed most critically tied to survival from egg to hatchling. Two life tables were most similar to one for an Ohio population in survival to first breeding (5-12%), cohort generation time (1.8 yr), and age two contributing most to the net reproductive rate.