Seasonal Color Plasticity in Hyla savignyi as a Potential Adaptation to Mediterranean and Semi-Arid Environments

The Middle East tree frog, Hyla savignyi, occupies Mediterranean and semi-arid habitats that change markedly from green during the rainy season to yellow-brown during the dry season. This narrative review evaluates whether seasonal dorsal-color variation may contribute to environmental matching. Evidence was synthesized from field observations in northern Israel, a controlled substrate-use experiment, and comparative studies of physiological color change in amphibians. Field records show green, pale, brown, and dark frogs in seasonally contrasting habitats, whereas experimental observations show nonrandom substrate use and a strong association between frog color and occupied substrate. These findings are consistent with background matching, but they do not establish rapid physiological color change, reduced predator detection, or improved survival. Substrate treatments also differed in vegetation structure and microclimate, preventing color from being isolated as the sole cue. Chromatophore-mediated pigment redistribution provides a plausible reversible mechanism, but this mechanism has not yet been demonstrated directly in H. savignyi. Seasonal color plasticity and microhabitat selection are therefore best regarded as complementary, testable hypotheses for adaptation to Mediterranean seasonality. Controlled experiments using standardized substrates, repeated objective color measurements, and predator-vision models are needed to distinguish color change from background choice and to quantify adaptive value.