Geographic variation in acoustic and visual cues and their potential to signal body condition in the Brazilian treefrog, Boana albomarginata

Abstract

Anuran communication is largely based on acoustic signals, but different sensory modes are also widespread, including visual communication using body color traits as a way of signaling. The Brazilian treefrog, Boana albomarginata, has a complex behavioral repertoire presenting several call types and performing gestures as visual signals. This species has a greenish body color with orange patches on the flanks and thighs. These patches become visible when males are in a calling posture or performing visual signals such as leg kicking and limb lifting, suggesting that they might use the patches as visual cues. We sampled seven populations, using call recordings and photographs to access males call and color traits. We demonstrate that there is variation in color and call properties across populations. Additionally, we observe variation in the relationship between color traits and call properties in different populations, revealing that only two populations exhibit a significant correlation between color and call traits. Further, while call properties and color traits were not related with individual body size, they were associated with body condition. The results indicate a universal pattern across populations for call properties, wherein males in better condition consistently displayed lower-pitched calls, longer calls, and shorter intervals between calls. Regarding color traits, males in better condition in four out of the seven evaluated populations exhibited larger orange patch sizes, lower orange hue values, and higher hue contrasts. Although we observed some level of relation among color, call, and body traits, there is not a universal pattern across all populations.

Significance statement

Animal social interactions are mediated by signals transmitted through different sensory modes (i.e., acoustic, chemical, tactile, and visual), and more than one of these modalities can compose the behavioral repertoire of one species. Using photographs and acoustic recordings of Boana albomarginata males in natural environments, we documented geographic variation in both signals, call and color, and investigated their potential to convey individual body size and condition. Our findings reveal that both signals were correlated with individual body condition. In addition, color traits were associated with call properties in some populations.