The Effects of Acoustic Signalling on Male Spacing Behavior in the Sagebrush Cricket: Are Signals used in Territorial Defense?

Abstract

Acoustic signalling in orthopterans functions in mate attraction and/or intermale spacing. The pattern of intermale distances should reflect the degree to which signalling functions in territorial defense. Males who are unable to detect, and thus respond to, the signals of rivals should be at greater risk of inadvertently intruding on the territories of rivals and of being intruded upon. We tested, in two field mark-recapture experiments with the sagebrush cricket Cyphoderris strepitans, the hypothesis that acoustic signals are used in intermale spacing, predicting that deafened males are compromised in their ability to repel rivals and should thus be found in closer proximity than control (hearing) males. There was no difference in mating success between deaf and control groups. There was a difference in nearest-neighbor distance between deaf and control animals in one replicate of one experiment and in one night of one replicate of the other experiment. These results suggest that calling has a sporadic effect on spacing behaviour of sagebrush crickets and thus primarily functions in mate attraction. The results are discussed in the context of the mating system of sagebrush crickets and the economics of territory defense.