Effects of traffic noise on calling activity of Aplastodiscus leucopygius (Anura, Hylidae)

Advertisement calls are the main communication form of anurans, and other individuals can use it to evaluate several aspects of the calling individual. In this context, environmental disturbances, such as traffic noise, can potentially affect this recognition. Therefore, this study aims to evaluate the response of Aplastodiscus leucopygius to traffic noise in a fragment of Atlantic Forest within the city of São Paulo. The experimentation consisted of recording the calling individual previously, during and after an exposure to urban noise. After that, individuals were measured to evaluate the Scaled Mass Index (SMI), and individual and environmental temperatures were taken. Also, considering that individuals of this species present harmonic shifting, we tried to evaluate which factors (individual, acoustic, or environmental) are associated with this phenomenon. We observed that the individuals showed an increase in call activity after exposure to traffic noise, but none of the evaluated aspects here could explain the harmonic shifting in their calls. Considering that this increasing on call activity also means an increasing of individual’s expense of energy, traffic noise is potentially harmful to the communication of A. leucopygius and, consequently, to its permanence in the site

Supplementary material to BEH 3780

Video 1. Experiment with an individual of Boana albomarginata in a view from above, showing the four speakers with high, medium and low-pitched calls and the white noise. A white circle indicates the individual of the trial. Figure A1. Frequency response of speakers used in the experiment (Frequency axis is in log scale).  Figure A2. Average percentage of pixels in each colour bin of photographs with their respective 5% confidence interval. Figure A3. Density plot between Scaled Mass Index (SMI) and orange and red colours.</p

Hidden shifts in allometry scaling between sound production and perception in anurans

Background Animal communication consists of signal production and perception, which are crucial for social interactions. The main form used by anurans is auditory communication, in most cases produced as advertisement calls. Furthermore, sound perception happens mainly through an external tympanic membrane, and plays an important role in social behavior. In this study, we evaluated the influence of body and tympanic membrane sizes on call frequency across the phylogeny of anurans. Methods We use data on snout-vent length, tympanic membrane diameter, and dominant frequency of the advertisement call from the literature and from natural history museum collections. We mapped these traits across the anuran phylogeny and tested different models of diversification. Our final dataset includes data on body size, tympanic membrane size, and call dominant frequency of 735 anuran species. Results The best explanatory model includes body and tympanum size with no interaction term. Although our results show that call frequency is strongly constrained by body and tympanum size, we identify five evolutionary shifts in allometry from that ancestral constraint. We relate these evolutionary shifts to the background noise experienced by populations. Body size is important for myriad ecological interactions and tympanum size is strongly associated with female call frequency preferences. Thus, allometric escape in frog calls might arise through environmental selection such as breeding in fast flowing or soundscape competition, as well as sexual selection linked to tympanum size

Size per locality.

<p>Mean of SVL for each species by locality and number of examined specimens.</p

Island versus mainland populations.

<p>Species that presented significant size difference in islands: <i>Adenomera marmorata</i> (A: Mainland and D: Ilha da Marambaia), <i>Ololygon trapicheiroi</i> (B: Mainland and E: Ilha Grande) and <i>Boana albomarginata</i> (C: Mainland and F: Ilha de Itanhangá) (scale: 1 cm).</p

Thermal mismatch explains fungal disease dynamics in Brazilian frogs

Theory predicts that susceptibility to disease in ectothermic hosts increases as temperatures depart from host’s thermal optima, because pathogens have functionally broader thermal tolerance ranges and acclimate faster than hosts to shifts in temperature. Hence, hosts adapted to cooler and warmer climates should be at greater risk of infection under abnormally warm and cool conditions, respectively. Batrachochytrium dendrobatidis (Bd) is a chytrid fungus that affects amphibians worldwide. In Brazil's Atlantic Forest, Bd outbreaks have been linked to numerous declines in amphibian populations, particularly in cooler high elevation areas. Thus, we hypothesize that years with abnormally warm temperatures could shift the balance in favor of the pathogen, thereby driving the historical declines. We also hypothesize that warm-adapted amphibians from lowland sites could experience elevated Bd infection risk during abnormally cold years. To test whether thermal mismatch (elevation vs. temperature anomaly) drove shifts in Bd prevalence through time we compiled a comprehensive database spanning 50 years, gathered across an elevational gradient within the Atlantic Forest. In agreement with our predictions, cool-adapted hosts had higher Bd prevalence when temperatures were higher than historical averages. In parallel, Bd prevalence in warm-adapted hosts was higher in colder-than-average years, although frogs from higher elevations exhibited an overall higher risk of disease due to disproportionally high infection prevalence. Our study links the thermal mismatch hypothesis with historical shifts in Bd prevalence in Brazilian frogs, indicating that Bd infections, modulated by climate change, may continue to have a negative impact on Neotropical amphibians

Collecting sites.

<p>Distribution of populations sampled in this study in <i>Costa Verde</i>, state of Rio de Janeiro.</p

Allometric shifting.

<p>Principal Components Analysis (PCA) considering each island and mainland populations for each species.</p