The perils of city life: Patterns of injury and fluctuating asymmetry in urban lizards

Animals that live in cities face a number of challenges particular to the urban environment that may impact on overall health and survival. Nevertheless, relatively few studies have investigated injury and health in urban species. We measured body condition, injury rate and fluctuating asymmetry in urban and forest populations of the tropical lizard Anolis cristatellus. We found that although there were strong differences in body condition between urban and forest populations, the direction of this difference varied between municipalities. We also found that injury rates (amputated digits and bone fractures) were slightly, but significantly, more common in urban populations; this phenomenon may be due to changes in intraspecific interactions or predation pressure in urban sites. Contrary to our expectations, we found that fluctuating asymmetry was greater in forest compared to urban populations. Because our data were collected from adults, this may be a sign of stronger natural selection on the symmetry of functional traits in urban than in forest environments. Finally, we found no persuasive evidence that city living is inherently detrimental to individuals of this species despite a slightly higher rate of injury. Being able to overcome the challenges of city life may be integral to urban persistence and a step along the path to urban adaptation.