Competitive masking of vibrational signals during mate searching in a treehopper

Mate localization in insects that use acoustic, vibrational or visual displays often involves a male–female duet. Female signals provide cues not only to the duetting male, but also to competitors that may attempt to disrupt the duet. Mate localization based on substrate vibrations may be especially vulnerable to such disruption, because localizing vibrations is difficult, and mating success often depends on localization efficiency. We tested the hypothesis that a specialized signal produced by male treehoppers, Tylopelta gibbera, disrupts competitors’ duets. This hypothesis predicts that the signal occurs during competition to locate a female, and that it decreases the frequency of female responses. We first characterized the search paths of single males duetting with a female. Males walked along host plant stems, frequently stopping and producing signals that elicited female replies. Males made forward/reverse decisions only after the female responded and their accuracy decreased with distance from the female. We then characterized the behaviour of two males duetting with the same female. Single males never produced the putative disruption signal, but pairs of males frequently did, timing it to overlap with the rival’s signal. The overlapping signal strongly decreased female responses, both during natural signalling interactions and in response to playbacks. Males took longer to localize the female in the presence of a competitor. The overlapping signal apparently functions to reduce the directional information available to competing males, probably through signal masking. This is one of the few experimental demonstrations of a specialized signal whose function is to disrupt communication.