Trade-offs in signalling components differ with signalling effort

Many animals use acoustic signals to attract potential mates but are simultaneously exposed to acoustically orienting predators or parasitoids. Given the conflicting selection pressures on signal components, males that signal often might be forced to make trade-offs among these signalling components to reduce their risk of becoming prey, or because of energetic, biomechanical, or physiological limitations. We explored the conditions under which males make trade-offs among components of signalling effort in the Texas field cricket, Gryllus texensis. Male Texas field crickets show extensive variation in the effort they allocate to mate attraction. We predicted that males with high and low signalling effort should show different covariances among the number of bouts produced per hour, average bout duration and average trilling amplitude. We found that high-effort males showed strong trade-offs between bout duration and hourly bout number and between trill amplitude and hourly bout number, whereas low-effort males showed no trade-offs between any of their trilling components. Our results suggest that males using different signalling efforts may experience different selective regimes on their trilling behaviour.