Acoustic Phenotypes of an Alpine European Common Frog Population

In this work we studied the acoustic variability in the induced release call on wild populations of the European common frog Rana temporaria. We used a computational model to analyze the induced release calls in both sexes. Our analysis detected three different acoustic phenotypes: (a) Non-canonical males comprised a large part of the population and were the main cause of the biased sex ratio (Phenotype 2), since (b) canonical males (Phenotype 1) and (c) canonical females (Phenotype 3) had close to a 1:1 ratio. Phenotype 2 were much more abundant in locations were tadpoles were exposed to high water temperatures during their development, suggesting that a masculinizing effect of temperature is responsible for the biased sex ratio, and a likely origin for “pirate” males which search for newly laid clutches to fertilize not fertilized eggs by the “parental” males.