Amplification of frog calls by reflective leaf substrates: implications for terrestrial and arboreal species

Signal detection is a fundamental requirement for any communicative interaction. Acoustic signals, however, experience amplitude losses during their transmission through the environment, reducing their detection range. Displaying from sites that increase the amplitude of the sound produced, such as cavities or some reflective surfaces, can improve the detectability of signals by distant receivers. We measured the effect of leaf calling sites on the calls of an arboreal (Hyalinobatrachium fleischmanni) and a leaf-litter specialist (Silverstoneia flotator) frog species. We collected the leaves where males of both species were observed calling, and conducted playback experiments to measure their effect on the amplitude of frog calls. Overall, the leaves used by H. fleischmanni and S. flotator were of similar dimensions, and amplified the calls of each species by about 5.0 and 2.5 dB, respectively. The degree of call amplification was unrelated to leaf dimensions or the position of the frogs on the leaves, but explained by the different frequency content of the calls of each species. We suggest that amplification of frogs calls by leaves could represent either a benefit or impose costs for arboreal and terrestrial species, which may depend on the spatial location of intended and unintended receivers