Do male field crickets, Gryllus pennsylvanicus, signal their age?

Abstract

Older males are often reported to have higher mating success than younger males. To the extent that male quality and survival are positively correlated, this observation raises the possibility that females use male signals to assess age and thus quality. I tested this hypothesis in the fall field cricket, Gryllus pennsylvanicus, a species in which females are known to prefer older males, and males call to attract females. Tests were both longitudinal (males recorded early and late in life) and cross-sectional (males recorded once, each at different ages). I measured a variety of temporal and spectral calling song parameters and tested the predictions that: 1) calling song changes with age, and 2) variation in calling song correlates with variation in age. I found significant changes with increased age: calls showed decreased pulse period, decreased pulse duration, decreased pulse peak frequency, more pulses per chirp and increased pulse period variability. Although pulse period and pulse duration were negatively correlated with male age in bivariate correlations, canonical correlation failed to detect any significant relationship between male age and any linear combination of song parameters. I also measured a number of male body size traits and found that the majority of information in male song appears to be related to body size. I discuss the results in relation to the auditory sensitivity of G. pennsylvanicus, and suggest a simple mechanism that explains both female preference for older males and female discrimination against heterospecific males.