Photo credit: arstechnica.com

Unraveling Spider Behavior Through Robotics

It is well known that spiders have limited visual capabilities, relying heavily on vibrations in their webs to detect captured prey, such as a fly. The web serves as an extension of their sensory perception, alerting them to movement. What remains less understood are the specific behaviors spiders engage in to find struggling prey. Notably, when prey is stationary, spiders often adopt a crouching stance, and may exhibit movements like bobbing or plucking the web using one of their legs. This crouching behavior appears to cease when the prey begins to move.

Studying this phenomenon can be challenging due to the myriad variables present when observing live spiders. To address this, a team at Johns Hopkins University’s Terradynamics Laboratory has turned to robotics, constructing crouching spider models for testing on synthetic webs. Their findings support the hypothesis that the crouching behavior allows spiders to discern variations in web frequencies, functioning similarly to echolocation. These initial results were shared at the American Physical Society’s Global Physics Summit held in Anaheim, California.

According to team member Eugene Lin, who spoke to Ars, the lab specializes in modeling biological behaviors through robotic simulations. “Animal experiments are incredibly difficult to replicate because controlling their actions can be unpredictable,” Lin explained. In contrast, robotic models allow for complete repeatability. This methodology not only provides clear experimental data but also enhances understanding of the biological systems being modeled, illuminating specific behaviors. Additionally, the lab has previously developed robotic models inspired by the movements of cockroaches and fish.

This research benefits from collaboration with two other laboratories at Johns Hopkins. Andrew Gordus’s lab focuses on spider behavior, particularly how different species construct their webs, offering biological insights and video documentation of the species in question, U. diversus. Jochen Mueller’s lab contributed expertise in silicone molding, facilitating the 3D printing of flexible joints for the robotic spider.

Crouching Spider: Harnessing Vibrational Sensitivity

The initial iteration of the spider robot was a static model, designed solely to detect vibrations within the synthetic web. Later advancements introduced actuators, allowing the model to move vertically. While the robot features only four legs, each with two joints and two accelerometers—compared to the eight legs and numerous joints of a real spider—it served as a successful proof of concept for the experiment. Alongside the spider robot, a stationary prey robot was also developed for testing purposes.

Source
arstechnica.com