Trade-off phenomena in calling song recognition and phonotaxis in the cricket,Gryllus bimaculatus (Orthoptera, Gryllidae)

Summary

• 1. The phonotactic tracking behavior of females on a locomotion compensator was studied in the chirping cricket,Gryllus bimaculatus De Geer. Synthetic stimuli were used in sequential stimulus-presentation paradigms to reveal the role of calling song temporal properties in eliciting phonotaxis.

• 2. Twelve out of 21 females did not track initial trills with an optimal syllable period (Fig. 2); five out of 13 females tracked initial tone bursts with no syllable rhythm (Fig. 4); and tracking of stimuli with syllable periods outside of the natural range could be turned on or off repeatedly by varying the values of the temporal properties of the calling song. These results show that syllable period is not always a sufficient and necessary parameter for eliciting recognition and phonotaxis inG. bimaculatus. Furthermore, several temporal properties of the calling song appear to be evaluated in the recognition process.

• 3. When trill tracking occurred, the syllable period was within its natural range in the calling song; trills with syllable periods outside of this range did not elicit tracking (Fig. 3). A trill with an ‘unattractive’ syllable period (i.e. outside natural range) could be made more attractive by adding a natural chirp rhythm (Fig. 3B). Tone burst tracking was dependent upon the stimuli having certain burst-duty-cycles (burst duration/burst period, Fig. 6), and this effective range corresponded to the effective tracking range of chirp-duty-cycles in the calling song (Figs. 10, 13).

• 4. The temporal property interactions that underlie recognition and the elicitation of phonotaxis were studied by varying two temporal properties while the other properties of the calling song were held approximately constant. The results showed that the behavioral ‘tuning’ to a particular temporal property was broad or narrow, depending on the values of other temporal properties. The optimum effective values of several temporal properties for eliciting phonotaxis were within their natural ranges in the calling song (Figs. 8–12).

• 5. The temporal property interactions that were apparent in the tracking behavior ofG. bimaculatus can be described by a ‘trade-off’ in which several temporal properties of the calling song contribute to the total attractiveness of the stimulus. When the phonotactic attractiveness of one temporal property is lowered, the attractiveness of the stimulus can be maintained by raising the attractiveness of other temporal properties. Each temporal property that is relevant in the recognition process probably has a different weighting in individual females and these weightings might vary among individuals.