Sunlight Sonata: Contrasting the Roles of Solar Ultraviolet Radiation and Temperature on the Calling Behavior of a...

Diurnal animals are frequently exposed to solar ultraviolet radiation (UV) during their daily activities, which can lead to DNA damage and other physiological challenges. To counteract these effects, they have evolved complex DNA repair mechanisms. The high energetic cost of DNA repair creates a trade-off with behavior, potentially constraining energetically demanding activities like anuran calling under harmful UV exposure. We tested hypotheses on how natural heterogeneity in the abiotic environment - particularly in the UV radiation - influences the calling behavior of Crossodactylus schmidti, a diurnal forest-specialist frog found in preserved neotropical streams. To gather data on male calling behavior, we used passive acoustic monitoring of a well-studied population, using a set of recorders and data loggers that measured short- and long-term cumulative doses of UVA and UVB, air temperature, light intensity and cloud cover during the austral summer. To investigate associations between the abiotic variables and proxies of calling behavior (occurrence, number, and duration of calls), we used a model selection approach based on generalized linear mixed models followed by model averaging of the best-supported models. We found that: 1) the probability of recording males in calling behavior decreased with increasing mean air temperature and cumulative UVB dose but increased with short-term (15-minute) UVB exposure; 2) the number of calls emitted by males decreased with increasing mean air temperature but increased with cumulative UVB dose; and 3) call duration decreased with increasing mean air temperature but increased with cumulative UVB dose at calling sites. Short- and long-term doses of UVA, on the other hand, did not influence any proxy of calling behavior. Our findings show that higher temperatures in months of peak calling activity consistently reduce calling behavior, while UVB exposure has more complex effects. Together, these results underscore the need to consider both thermal and ultraviolet components of sunlight when assessing how anurans respond behaviorally to abiotic heterogeneity under ongoing environmental and climatic changes.