Living in the city: Reproductive and population ecology of Green Iguanas, Iguana iguana (Linnaeus 1758), inhabiting an urban landscape in Colombia

Abstract

Understanding how species persist in urban landscapes can provide insights into the fate of biodiversity
affected by rapid and unplanned urbanization. While the ecological and conservation implications of urbanization have
been reasonably well studied for temperate species, relatively little is known for those in tropical latitudes, especially
Neotropical lizards. We investigated the life history, habitat use, and reproductive seasonality of Green Iguanas (Iguana
iguana) inhabiting an urban area in Colombia. Our analysis of age structure showed that the sex ratio in this population
was approximately 1:1 at birth and adulthood, suggesting that both sexes are experiencing similar selective pressures
over time. The presence of individuals of all size classes throughout the year is indicative of a stable population. Density
estimates based on linear transect data indicated that iguanas in the studied population occur at higher densities than
those in rural areas. This increased density might be related to some benefits of urbanization, including human trophic
subsidies and decreased predation and competence. The estimated growth rate was also higher than those reported for
populations in natural habitats, likely reflecting increased food availability. Iguanas in the study area apparently reproduce
twice per year, a pattern that might be explained by rainfall regime. Occupancy modeling revealed that contrary
to rural populations, urban Green Iguanas successfully exploit open grassy areas for feeding and basking, with tree cover
and built-up areas being key predictors of their occurrence. The ability of urban iguanas to modify some traits of their
basic ecology to cope with the challenges imposed by urbanization may be crucial for this species to persist or even
thrive in cityscapes.