Males tend to have larger heads than females, in part because of swollen jowls. Both sexes have 12-13 prominent pores arranged in a row on the underside of both thighs. These glandular structures secrete a waxy substance with which iguanas mark their territory and identify each other. This developmental modification probably enables the male to better grasp the female during copulation. An iguana's skin is entirely covered with very tiny scales.
Young iguanas are pale green with black-ringed tails.
They mature to a lighter, more earthy color, usually with dark vertical bars on the body and tail. Vision, hearing and the sense of smell are acute. In their natural environment, iguanas tend to be very wary, hiding or fleeing at any sign of danger. Iguanas are somewhat clumsy but accomplished tree climbers. They tend to bask by day on tree branches, often over water.