Disguise or surprise: spider antipredator adaptations as a function of the architecture of their webs

Abstract

Animals exhibit a variety of strategies to avoid predation; spiders are no exception. We explored whether webbuilding spiders that differ in the architecture of their webs exhibit morphologies or behaviors suggestive of antipredator strategies that trade-off with the degree of protection offered by their webs. Spiders build webs of 3 types: the more protected tangles and sheet-and-tangles, which are three-dimensional (3D), and the more exposed orbs, which are two-dimensional (2D), both with or without a refuge. We hypothesize that spiders whose webs offer greater protection—a 3D architecture or a refuge—will be less likely to be armored or brightly colored when compared to spiders without these protections. We collected data on 446 spiders and their webs in 2 lowland tropical rainforest sites. We show that 2D web builders with no refuges tended to be brightly colored (background contrasting) and spiny (spiky), whereas those with refuges tended to blend against the background of their refuges. 3D web builders, on the other hand, were neither cryptic nor brightly colored nor armored but were more likely to drop out of the web upon simulated predator contact. These results support the hypothesis that web-building spiders tend to be protected either through the architecture of their webs or their morphology and behavior, suggesting a trade-off between different types of antipredator strategies.