COMPARATIVE DEMOGRAPHY OF THE LIZARD BASILISCUS BASILISCUS

Abstract

Basiliscus basiliscus in two neighboring populations were marked and studied from 1971 to 1975. Females matured at about 135 mm SVL and 20 months of age. Seasonal reproductive activity began with the rainy season and remained at a high level for 7-8 months, followed by heightened activity at the beginning of the dry season and reduced activity late in the dry season. In 1973-1974, females in one population produced two extra clutches of large size. Survivorship of eggs was low at both sites, and life tables indicated declining populations with R& of 0.075 and 0.236. Both populations declined by about two-thirds during the study. Annual variation was detected in growth, juvenile survivorship, and the size-fecundity relation- ship. Neither r- nor K-selection explains the life history of this species. Basilisk demography seems to be most consistent with a model dominated by high and variable juvenile survivorship, which may be density-independent. Observed demographic characteristics may reflect interac- tions between environments and gene pools, and may vary at the microgeographic level. Broad geographic comparisons could be jeopardized by such local variations.