Tolerant pattern recognition: Evidence from phonotactic responses in the cricket Gryllus bimaculatus (de Geer)

When the amplitude modulation of species-specific acoustic signals is distorted in the transmission channel, signals become difficult to recognise by the receiver. Tolerant auditory pattern recognition systems, which after having perceived the correct species-specific signal transiently broaden their acceptance of communication signals, would be advantageous for animals as an adaptation to the constraints of the environment. Using a well-studied cricket species, Gryllus bimaculatus, we analysed tolerance in auditory steering responses to non-attractive “Odd” and “Silent” chirps by employing a fine-scale open-loop trackball system. Odd chirps on their own did not elicit a phonotactic response. However, when inserted into a calling song pattern with attractive Normal chirps, the females’ phonotactic response towards these patterns was significantly larger than to patterns with Silent chirps. Moreover, females actively steered towards non-attractive Odd chirps when these were presented wit...