ECOLOGY AND LIFE-HISTORY OF THE VIVIPAROUS LIZARD MABUYA-BISTRIATA (SCINCIDAE) IN THE BRAZILIAN AMAZON

The viviparous lizard Mabuya bistriata was studied in two lowland tropical forest sites in Amazonian Brazil with additional data taken on museum specimens. These diurnal lizards are active primarily during mid- to late morning on fallen logs or low on tree trunks. They are heliothermic averaging 32.9 +/- 0.98 C in body temperatures. Prey include orthopterans, spiders, eruciform larvae, termites, and other invertebrates. Prey differences between the two sites most likely reflect differences in prey availability associated with tropical seasonality in rainfall. Mabuya bistriata reach sexual maturity by the end of the first year of life, and females produce their first brood at an age of one yr. Females have larger body size than males, and males have larger head size than females. Females ovulate ova 1 mm in diameter and 0.47 mg dry mass. A chorioallantoic placenta forms through apposition of the chorioallantois to the uterine mucosa. During gestation, dry and wet mass increase by over 47,400% and 74,700%, respectively, with virtually all nutrients for development supplied by the female. Gestation lasts 9-12 months. Brood size varies from 2-9, and females with near-term embryos are heavier and wider than nongravid females suggesting a potential cost to reproduction related to the effect of clutch mass and volume on locomotor abilities.