Extended Phenotype Influences Collective Behaviour and Survival in a Social Spider

Abstract

Increasing human interference has been shown to not only destroy habitats, but also alter the architecture of animal-built extended phenotypes. However, the impact of such architectural changes on the behaviour and survival of organisms remains poorly understood. To address this knowledge gap, we examined the impact of habitat modification using Indian social spider, Stegodyphus sarasinorum, as a model organism. S. sarasinorum colonies typically construct a three-dimensional (3D) capture web. Due to increasing habitat modification by humans, these spiders are now constrained to build two-dimensional (2D) capture webs adapting to man-made structures like fences. We investigated how these differing web architectures influence the collective behaviours and survival of S. sarasinorum. Our findings reveal that spiders with 2D capture webs emerged from their nests sooner, attacked prey faster, and had higher number of attacking spiders compared to those with 3D webs, suggesting 2D webs may be more efficient for hunting. However, despite their hunting advantages, spiders in 2D webs more frequently attacked the dangerous body parts of honeybees and were susceptible to honeybee stings. These results suggest that human-induced architectural modifications of the extended phenotype can have both benefits and costs for the organisms that built it. The survival benefits conferred by 3D capture webs against risky prey may have played a significant role in the evolutionary selection of this web architecture in S. sarasinorum.