Effects of Leaf Moisture on Transmission and Detection of Communication by a Wolf Spider

Abstract

In the multimodal communication of Schizocosa ocreata wolf spiders, males respond to chemical signals from females with visual and substrate-borne vibratory signals for courtship. We examined the effect of wet vs. dry leaves on transmission of male courtship signals, responses of male spiders to female chemical cues, responses of courting males to bird calls indicating predator presence, and mating success. Laser Doppler vibrometry showed that spider stridulation and percussive signals maintain higher amplitude over distance on dry leaves than on wet leaves. Male response to chemical cues (courtship latency and rate) declined after leaves with female silk became wet. In response to predatory bird calls (Blue Jays) transmitted through leaf surfaces, courting male spiders on dry leaves responded with anti-predator “freeze” behaviors more often and with longer duration than those on wet leaves, and with longer latency to return to courtship on wet leaves. Laser Doppler vibrometry confirmed that bird calls on dry leaves had significantly greater average amplitude and different spectral profiles than those on wet leaves. Males courted females on wet and dry leaves with equal frequency, but subsequent mating success was significantly greater on dry leaf litter. Interestingly, visual signals increased on wet leaves, suggesting compensatory behavior in response to moisture. Given a predicted change in precipitation in parts of North America because of global climate change, these results suggest potential for impact on behavior of invertebrates at the microhabitat level.