Influence of urban noise in call traits of the Atlantic Forest treefrog Bokermannohyla hylax

Abstract

Anurans commonly use sound signals as the main form of communication. This system is diverse in both structure and social functions, and can be used from mate recognition until evaluation of conspecifics. Consequently, when in noisy environments, the main constraint is to correctly identify acoustic signals. Thus, this study aims to evaluate the influence of traffic noise in call parameters of Bokermannohyla hylax. We recorded individuals in collecting sites closer and further from the boulevard, inside the area of Parque Estadual das Fontes do Ipiranga, an urban Atlantic Forest fragment at municipality of São Paulo, Brazil. We evaluated if noisy or silent collecting sites influence temporal and spectral variables and signal-to-noise ratio. As expected, we observed influence of collecting site on temporal variables and on signal-to-noise ratio, but not on spectral variables. Spectral traits, unlike temporal ones, are more related to intrinsic aspects of individuals, and consequently they tend to present limited or no modification in face of anthropogenic noise. We also observed an influence of traffic noise on signal-to-noise ratio, which means that if the traffic noise is more intense, individuals increased calling power amplitude. This increase has several implications in different aspects of the life of individuals, even influencing the spent of energy in other anuran life story traits. Consequently, traffic noise can impact the long-term permanence of the species in highly noisy environments.