Cockroaches use diverse strategies to self-right on the ground

TL;DR

This study compares self-righting strategies of three cockroach species on low-friction surfaces, revealing diverse mechanical approaches and the importance of rotational energy and rolling in successful righting.

Contribution

It provides a detailed biomechanical analysis of self-righting strategies across species, highlighting the diversity and mechanical principles involved.

Findings

All species nearly always self-righted within 30 seconds.

Successful self-righting often involved rotational kinetic energy and rolling.

Different species used body deformation, leg forces, and wings for self-righting.

Abstract

Terrestrial animals often must self-right from an upside-down orientation on the ground to survive. Here, we compared self-righting strategies of the Madagascar hissing, American, and discoid cockroaches on a challenging flat, rigid, low-friction surface to quantify the mechanical principles. All three species almost always self-righted (97% probability) when given time (30 seconds), frequently self-righted (63%) on the first attempt, and on that attempt did so in one second or less. When successful, two of the three species gained and used pitch and/or roll rotational kinetic energy to overcome potential energy barriers (American 63% of all attempts and discoid 78%). By contrast, the largest, heaviest, wingless cockroach (Madagascar hissing) relied far less on the energy of motion and was the slowest to self-right. Two of the three species used rolling strategies to overcome low potential energy barriers. Successful righting attempts had greater rolling rotation than failed attempts as the center of mass rose to the highest position. Madagascar hissing cockroaches rolled using body deformation (98% of all trials) and the American cockroach relied on leg forces (93%). By contrast, the discoid cockroach overcame higher and a wider range of potential energy barriers with simultaneous pitching and rolling using wings (46% of all trials) and legs (49%) equally to self-right. Our quantification revealed the performance advantages of using rotational kinetic energy to overcome the potential energy barrier and rolling more to lower it, while maintaining diverse strategies for ground-based self-righting.