Virgin Male Mating Advantage in Sagebrush Crickets: No Role for an Acoustically-Mediated Female Preference

Abstract

The sagebrush cricket, Cyphoderris strepitans, is one of only five extant species belonging to an obscure orthopteran lineage, the Haglidae, closely related to the true crickets (Gryllidae) and katydids (Tettigoniidae) (Morris & Gwynne 1978). C. strepitans occurs exclusively in mountainous areas of the western United States, where it is found primarily in high-altitude sagebrush meadow habitat. Adults become sexually active in late spring, shortly after snow melt, and remain active for the following 4-6 weeks. The acoustic signals produced by males function to attract females (Snedden & Irazuzta 1994), thereby enhancing male mating opportunities (Snedden & Sakaluk 1992). Copulation is initiated when a receptive female climbs onto the dorsum of a male, at which time he attempts to transfer a spermatophore. During copulation, the female feeds on the male's fleshy hind wings and bodily fluids leaking from the wounds she inflicts. Previous field studies involving the mark­recapture of a large number of males have shown that once a male has mated, his probability of obtaining an additional copulation is reduced relative to that of a virgin male securing his first mating (Morris et al. 1989). One explanation for the virgin-male mating advantage is that non-virgin males, having lost a substantial portion of their energy reserves through sexual cannibalism by females and the transfer of a large spermatophore, may be unable to sustain the costly acoustical signaling activity required to attract additional females. In support of the "male fatigue" hypothesis, electronic assays of male signaling behavior have shown that virgin male C. strepitans call for significantly longer durations than recently mated males (Sakaluk et al. 1987; Sakaluk & Snedden 1990).