Spider Trained to Jump on Command Reveals Insights On Hydraulic Power

Spiders have a bad reputation, but maybe that’s just because we humans are jealous. We can’t smell with our feet or hear with our leg hairs, and we definitely can’t leap a distance up to six times our body length from a standstill. The best we can do is get up to 1.5 body lengths, and if you’re doing that, you’re probably going to the Olympics. What we can also do is study the spider in the hopes of building a new class of agile micro-spider-robots to do our bidding, which was the point of a spider locomotion study released Tuesday in Scientific Reports.

In the paper, scientists from the University of Manchester describe a study that arachnophobes will find unsettling. They bought three female Phiddippus regius spiders — known also as regal jumping spiders — from a pet shop called Urban Jungle and successfully trained one of them to jump around to different heights and distances in a lab. They named the spider Kim, and what they learned from her both informs robot design and provides a deeper understanding of why jumping spider anatomy evolved the way it did. “The force on the legs at take-off can be up to five times the weight of the spider — this is amazing and if we can understand these biomechanics we can apply them to other areas of research,” said study co-author Bill Crowther, Ph.D. in a statement released Tuesday.

There are approximately 5,900 species of jumping spiders, but Kim is seemingly the only one that’s been trained to jump around by scientists. In the study, Kim was “manually transported between the take-off and landing platforms until it became familiar with the challenge” and “no form of stimulation (e.g. air blowing) was used to induce a jump.” They recorded her jumps with ultra-high-speed cameras and used high-resolution micro CT scans to create a 3D model of Kim’s legs and body structure.

Doing so allowed them to take a closer look at the biomechanics of her jump, with a special emphasis on the force. They saw that how she jumped depended on the situation. When jumping short distances, Kim spent more energy on a faster, lower-trajectory jump; for longer, higher jumps, she aimed herself in a way that would use as little energy as possible. Crowther explains that “whilst Kim can move her legs hydraulically, she does not need the additional power from hydraulics to achieve her extraordinary jumping performance.”

The team’s discoveries about the physics of Kim’s jumps could prove to be useful for creating synthetic muscles to make robots jump. “We find that the jump power requirements can be met from the estimated mass of leg muscle; hydraulic augmentation may be present but appears not be to be energetically essential,” the team writes.

Kim’s energy-focused short-jump may also be connected to her large anterior-facing eyes, which give her good, but limited eye sight that becomes worse the larger the distance between her and the target gets. In June, scientists said that jumping spiders like Kim could likely see all the way to the Andromeda galaxy, but that doesn’t mean they would be willing to take the leap.