Land Ho! Polarized light serves as a visual signal for landward orientation in displaced spiders

An organism’s ability to identify goals within their environment, orient towards those goals, and successfully navigate to them are critical to all aspects of survival. Long-jawed orb weavers (Tetragnatha elongata) occupy riparian zones and perform orientation behaviors when displaced from this habitat onto the water. Spiders prefer to move toward the closest shoreline, regardless of release location, likely to avoid predation from fish. In this study, we conducted a series of investigations to determine the mechanism by which these spiders rapidly achieve zonal recovery. Occlusion experiments indicate that spiders use visual information to identify characteristics of the riparian habitat and navigate to shelter. While environmental characteristics such as color, contrast, and the sun’s position do not appear to factor into this orientation behavior, the polarization of light appears critical. We propose that the polarization of light reflecting off the water’s surface acts as a water detector and the absence of such at the edges of the pond (or via experimental induction) serves as a visual reference for the closest suitable habitat.