O efeito dos ruídos antropogênicos sobre o canto de anúncio de anuros no Município de Cruz das Almas, Bahia

Abstract

In anurans, acoustic communication has a great importance in the social organization of individuals, playing a relevant role in the conquest of reproductive partners and in the defense of territory. Noise pollution can directly affect the communication of these animals, reducing the efficiency in the range and quality of emitted vocalization, which can compromise reproductive success, predator detection and territory defense. Still, these animals may have adaptations that reduce sound masking by environmental noise. The objective of this work is to investigate the strategies used by males of four species of anurans to avoid masking their ad singing in the face of anthropogenic noises. Acoustic information was collected from male singers and ambient noise in the city of Cruz das Almas, Bahia. For this, collections were performed between August and October 2019. Points were previously selected within the city that met two criteria, males in acoustic activity and flow of vehicles and people, as well as other sources of anthropogenic noise. Announcement corners and anthropogenic noises were analyzed using the Raven Pro 1.5 program and two TASCAM DR-05 recorders were used to record the song and noise consecutively. Principal component analyzes (PCA) were used to establish which parameters of the ad corner were most relevant to explain their variation. Subsequently, Mann-Whitney tests were performed with these variables to verify differences in the advertisement corner of animals present in the urban and nonurban environment. We verified the relationship between the announcement song of each species and the anthropogenic noises. For this we performed a stepwise regression analysis (forward) between the ad corner variables selected in the PCA and the anthropogenic noise variables. Finally, we used the variables selected in stepwise regression in a multiple regression model to verify the anthropogenic noise variables that explain the variations in the anurans' announcement corner. Analyzes were performed using the Past 3.14 program. It was observed that the urban populations presented acoustic differences when compared to the non-urban population, mainly in the dominant frequency, number of harmonics and note duration. In addition, L. trlogodytes singing was correlated with anthropogenic noise, demonstrating that males of this species respond directly to the amount of noise that is exposed. Thus, we concluded that it was necessary acoustic adjustments in the announcement corner of the species so that they could be adapted to the urban environment, corroborating the hypothesis of acoustic adaptation proposed by Morton (1975).