Traffic noise leads to cardiac stress reactions in two urban-tolerant Trichonephila spiders, but in different ways

Abstract

Human-generated traffic noise can increase stress levels in wild animals, which may underlie fitness declines. And prior exposure to noise may influence an individual's response. While much research has examined noise-induced stress on vertebrates, much less is known regarding invertebrates. We tested the hypothesis that traffic noise affects spider stress. To accomplish this, we measured heart rate elevations in two orb-weaving Trichonephila spiders in the United States, the non-native jorō spider (Trichonephila clavata) and the golden silk spider (Trichonephila clavipes). Mature females were captured along roads at natural areas with either prior exposure to loud noise with high daily traffic patterns or quiet sites with low daily traffic patterns and housed in clear containers in a lab. For traffic noise playbacks, we broadcast a simulated pink noise signal at captive spiders and monitored their heart rate via contractions of the dorsal vessel, which we monitored remotely by a high-magnification video. Jorō spiders with prior exposure to loud traffic had the largest increase in heart rate. In contrast, the magnitude of heart rate change for golden silk spiders was predicted by baseline heart rates, regardless of prior noise exposure. Despite the change in heart rate, for both species, observed elevations following exposure to traffic noise were less than that observed when they were subjected to severe stress. Thus, our research adds to a growing body of literature that shows orb-weaving Trichonephila spiders tend to be resilient to anthropogenic disturbance, and their mild stress responses may underlie their ability to cope with human-generated environmental change.