We examined aspects of natural history and ecology of the black-chested spiny-tailed iguana, Ctenosaura melanosterna, on Cayo Cochino Menor, Honduras, over 6 years to provide baseline data to assist in management of this critically endangered species. Size of territory is resource-dependent, and the species seems to prefer habitats with open canopy. Mating occurred between March and June, with emergence of hatchlings from June to August. Ctenosaura melanosterna is an omnivore that feeds on a variety of vegetation, invertebrates, vertebrates, and food-scraps. The threats to this population include predation by Boa constrictor, competition with an increasing population of Iguana iguana, and potential poaching of adults and eggs for food.