The Utila iguana is the only species of iguana and one of only two species of lizard to exclusively inhabit brackish mangrove swamps, forced there due to competition from larger species. It is the smallest of the three species of iguana found on Utila, and unique among spiny-tailed iguanas as it is born a dark color as opposed to bright green or yellow. It is arboreal and primarily herbivorous, although it can be an opportunistic carnivore. Males may grow up to in length, while females are smaller, with a length of up to . Eggs are laid in sandy beaches and hatch about 60–76 days later, with the hatchlings returning to live in the mangrove forests.