Black widow spiders use path integration on their webs

Abstract

Many animals store information about their external environment in memory and use this information to facilitate movement and decision-making. The information used to navigate has been described for numerous animals and is dependent on the ecology of the animal. Spider webs make up nearly all of a spider’s physical and sensory environment. Here, we first asked whether black widow spiders form memories of their web and then asked whether the contents of these memories include a path integration vector. Black widows made navigational errors when we rotated their web in their absence and searched about the web upon realizing they made an error. Black widows were able to move on their web without retracing their steps, often taking shortcuts to a goal location without sensory cues to guide navigation. Black widows also began moving back to their retreat on a path parallel to their path out from the retreat, even after being moved on the web, and searched about the web for the retreat after not finding it initially. These results show that black widows use path integration when navigating. These results suggest that using internal representations of an animal’s position within its environment, such as by using path integration, is widespread among animals with varied brain types and sensory ecologies, representing perhaps a convergent solution to common navigational problems. The ability of animals to store information in memory that is then used in decision-making has evolved multiple times, in vertebrates and invertebrate lineages. The information and cognitive mechanism used for representing an animal’s location within its environment vary in complexity, but the methods that have been described rely on vision for at least some of the sensory information used to form representations. Using behavioral assays, we have shown that black widow spiders represent their position relative to their home as a path integration vector. Black widows have poor vision and rely primarily on vibrations transmitted through the web to sense their environment. Our results indicate that internal representations are a general solution to brains’ problem of integrating sensory information, and do not need acute vision to evolve.