Anthropogenic habitat modification linked to deformities in cururu toads from fernando de noronha

Body deformities are often linked to environmental disturbances when the proportion of affected individuals exceeds 10% of the population. Thus, amphibians can help improving both ecosystems and human welfare. We studied a potential cause of deformities in an introduced population of toads on a Brazilian island where the prevalence exceeds 50%. We inspected individual toads for external and internal morphological anomalies and tested for links between anthropogenic habitat disturbance and the frequency of deformities. We then compared deformity data from the Fernando de Noronha Islands with data from other invasive toad populations in the USA, the Bermudas and Brazil, recording novel deformities and summarizing historical trends of its prevalence over the past decade. We furthermore investigated partial and total blindness, and found strong evidence that eyes are lost during the post-metamorphic stage (adulthood) rather than being an innate deformity. High concentrations of environmental pollutants in more urbanized areas on Fernando de Noronha have likely led to increased anomalies in toads sampled from highly disturbed habitats. We discuss other potential causes that may be acting synergistically to drive one of the highest rates of deformities observed in vertebrate populations.