Attractiveness of grasshopper songs correlates with their robustness against noise

Long-range communication signals commonly serve to attract mates. Evolution of such signals was channeled by 2 classes of constraints: signals have to be conspicuous against background noise and signals should enable the receiver--in particular females that invest heavily in offspring--to assess the sender's quality and attractiveness as a sexual partner. However, as noise in the transmission channel likely conceals quality cues present in signals, these goals may represent opposing selective forces. We explored how noise affects the preferences of choosy female grasshoppers toward the communication signals of individual males. Our prediction was that male signals would become less distinguishable with increasing noise levels and, hence, female preferences for attractive signals would disappear. Here, we show that, contrary to this prediction, the differences in attractiveness between natural male songs were preserved even at high noise levels: the most attractive signals were at the same time particularly robust against masking. We discuss these results in view of a sensory exploitation scenario and a potential reduction of females' costs of choosiness. Copyright 2011, Oxford University Press.