The transmission of advertisement calls in Central American frogs

Acoustic communication signals change over distance due to loss of amplitud e and fidelity and it is assumed that signal degradation influences the rec eiver's ability to detect and decode signals. The degree of degradation dep ends on the signal's structure and the environment through which it transmi ts. We broadcast the advertisement calls of 22 species of Central American frogs at two heights within forested and open environments in Panama. We re corded these calls at five distances from the source and estimated signal d egradation with a cross-correlation analysis, a measure that combines the e ffects of decrement in signal amplitude and fidelity. Calls degraded less w hen broadcast higher above the ground compared to on the ground, and less i n open habitat compared to forested habitat; there was an additional intera ction between height and environment. Furthermore, calls with low dominant frequencies experienced less degradation than calls with high dominant freq uencies. There was no evidence, however that the calls of these frogs have evolved to maximize habitat-specific transmission.