Contrasting energetic costs of courtship signaling in two wolf spiders having divergent courtship behaviors

Energetic costs of courtship behavior were measured for two sympatric wolf spiders that are reproductively isolated based on distinct male courtship behaviors with different signaling modes and activity levels: Schizocosa ocreata (Hentz 1844) uses multi-modal communication (visual and seismic signals) and an actively-moving courtship display, whereas S. rovneri (Uetz & Dondale 1979) uses only seismic signals produced while stationary. To test for increased energetic expense of more complex multimodal courtship in S. ocreata, we recorded peak CO2 output for male spiders standing, walking, or courting. We found that peak CO2 output while standing or walking was similar between species. Courtship behavior of S. ocreata produced greater peak CO2 output than these other behaviors, and was significantly greater than peak CO2 output of S. rovneri courtship, which was not different from that of locomotion. Hence, unequal energy expenditure related to the modality of the males' courtship displays resulted in different energetic costs for courting male spiders. Male courtship vigor may serve as a criterion for female mate choice in Schizocosa.