Sand goby females do not spawn with silent males - but do males sing out their condition and can female hear the song in a noisy environment?

Abstract

Males of sand gobies (Pomatoschistus spp.) spawn in shallow water and produce a courtship sound to entice females to spawn. Previous work on field-caught males shows that courtship sounds differ between males of different body condition and between species suggesting that females use acoustic information in mate choice. Here, we manipulated male body condition via feeding regimes and measured courtship and subsequent spawning decisions. Although male condition measured as lipid content differed significantly between feeding regimes, neither male visual courtship, acoustic courtship nor spawning success were affected. However, comparing the lipid content of the experimental males to field-caught males show that in nature, males are of similar condition to males in the low condition treatment group. Acoustic signals might be masked by anthropogenic noise. Thus, to test if noise may affect spawning success we exposed courting males to experimental noise, resembling boat noise. We found that females only spawned with males that produced courtship sounds and significantly less often when exposed to noise. We conclude that the information content of male courtship sound and how it relates to male condition remains elusive, but that acoustic courtship is essential for mating success, making sand gobies potentially vulnerable to noise pollution. These results will be discussed in the light of preliminary data from a field experiment using the same noise set-up where male mating success was unaffected by treatment, and a pond experiment where variation in male mating success was affected by low levels of playback noise