Effects of urbanization on Bothrops jararaca populations in São Paulo municipality, Southeastern Brazil

Abstract

Quantitative and qualitative alterations in the environment may have serious ecological consequences for populations of native species. Isolated forest fragments, such as those surrounded by highly urbanized areas, may function similarly to oceanic islands with differences in species diversity compared to mainland areas. These differences may include changes in prey availability and predator pressure, with consequent effects on growth and size of species that interact with those prey and predators. Here, we investigate body size, prey availability, and predation pressure in populations of Bothrops jararaca in two forest fragments within an urban environment in southeastern Brazil (a completely isolated, small forest fragment and a large, well-connected forest fragment). While we found no differences in mean body size or stoutness between the two populations, we did find larger specimens in the small isolated fragment. Prey availability and predator pressure also were significantly lower in the small isolated fragment. The urban environment significantly changes the population ecology between the two locations. These results suggest that lower food availability in the isolated fragment did not decrease the growth rate of B. jararaca, but the low predator pressure increased longevity, resulting in a higher proportion of large snakes in this population.