Competition and cooperation in a synchronous bushcricket chorus

Area of Science:

• Animal Behaviour
• Evolutionary Biology
• Bioacoustics

Background:

• Synchronous signalling in animal choruses can arise from cooperation or competition.
• Understanding the evolutionary drivers of synchrony is crucial for explaining complex acoustic interactions.
• The katydid Mecopoda elongata provides a model system to study the mechanisms of signal synchrony.

Purpose of the Study:

• To identify the mechanisms driving the evolution of synchronous signalling in Mecopoda elongata choruses.
• To investigate whether cooperation (increased amplitude) or competition (female preference for leaders) drives synchrony.
• To determine the role of signal timing and duration in female mate choice.

Main Methods:

• Recorded signal timing and communal signal amplitudes in small M. elongata choruses.
• Conducted female choice experiments using live males and song models.
• Modeled the active space and mating possibilities of synchronous versus solo singing males.

Main Results:

• Males frequently engaged in leader-follower signalling with an average time lag of 70 ms.
• Females preferred leading males and songs with a conspecific signal period (2 s).
• Synchronous signalling increased signal amplitude by ~7 dB but slightly reduced per capita mating opportunities.

Conclusions:

• Female preference for leading signals is the primary driver of inter-male competition for signal timing.
• Synchrony enhances signal amplitude, potentially compensating for reduced individual mating success.
• The study suggests a fitness benefit for males through a 'beacon effect' and explores stabilizing selection for follower roles.