A Dung Beetle Life: How Dung Beetle Roll a Ball?

Insect locomotion is a complex process which needs to coordinate many motor units in real time while simultaneously interacting with the environment. To gain a better understanding of the insects locomotion, leg coordination is one of the principles which has been widely studied in cockroaches, stick insects and ants. Various gaits underlying leg coordination have been found, including tripod, tetrapod, and metachronal wave. Interestingly, dung beetles roll a ball with a very unique leg coordination pattern compared to the insects locomotion, but little is known about their ball rolling gaits.

To address this problem, researchers investigated the ball rolling behaviour of dung beetle with a specie named Scarabaeus (Kheper) lamarcki. Behavioural experiments and video recordings were performed to extract the ball rolling gaits and leg trajectories and then using a statistical approach to analyse the gait patterns and identify the underlying rules for describing the patterns.

The researchers have discovered the rules describing the alternation of the front legs and protraction waves of the middle and hind legs. They found that while rolling a ball backwards, the front legs are decoupled or loosely coupled from the other legs, resulting in a non-standard gait, in contrast to previously described tripod and gallop walking gaits in dung beetles. This provides insight into the principles of leg coordination in dung beetle ball rolling behaviour and its underlying rules.

Gait pattern of dung beetle ball rolling behaviour. ⒸBrain Lab, VISTEC

The researchers hope that the proposed rules can be used as a basis for further investigation into ball rolling behaviours on more complex terrain (e.g., uneven terrain and slopes). Additionally, the rules can also be used to guide the development of control mechanisms for bio-inspired ball rolling robots.