Meeting Abstract

71.2  Monday, Jan. 6 08:15  Advertisement-call novelties in the frequency domain are not favored by stimulation of an untapped inner-ear organ HUMFELD, SA*; THOMETZ, B; GERHARDT, HC; University of Missouri; University of Missouri; University of Missouri humfelds@missouri.edu

The pre-existing sensory bias hypothesis predicts that novel signals providing greater sensory stimulation are favored by sexual selection. Frogs have two sensory organs in the inner ear that are sensitive to different frequency ranges: the basilar papilla (BP) (>1000 Hz) and the amphibian papilla (AP) (<1000 Hz). Many frog species produce high-frequency calls that only stimulate the BP, leading to the prediction that females of these species should prefer signals which stimulate the AP. In one of these, we tested whether spectral complexity in the frequency domain is favored by female preferences for call novelties containing low-frequency energy that stimulates the AP. We tested preferences of spring peepers (Pseudacris crucifer) using two types of novel computer-synthesized calls in two-speaker forced-choice experiments: advertisement calls with a bimodal spectrum (normal waveform, novel spectrum); single-peaked advertisement calls to which an extra two-peaked call component was appended (novel waveform, novel spectrum). Females did not prefer or avoid the two-peaked advertisement call relative to a normal single-peaked call. However, when spectral complexity was utilized in a novel call component, some low-frequencies elicited significant positive or negative phonotactic preferences. Taken together with similar findings in other species, these results do not provide strong support for the hypothesis that spectral novelty is favored in species lacking low-frequency communication elements, but more comparative studies of AP function are badly needed.