Burrowing in ghost crabs: a multifunctional behavior to inspire a new generation of robots.
The ghost crab (Ocypode quadrata) is a remarkably multi-functional animal. They can capture and manipulate prey, excavate complex burrows and run faster than any other land invertebrate- all with the same set of appendages. Among these tasks, burrowing encompasses a particularly wide range of behaviors, including specialized postures, locomotion in confined environments, and goal-directed manipulation of the substrate. By examining the biomechanics of the crabs’ burrowing behavior, we can gain insight into the general features that enable animal multi-functionality. Novel x-ray imaging methods, developed for this work, now allow us to examine ghost crab burrowing to an unprecedented level of detail. We find that the crabs possess a very diverse ‘tool kit’ of strategies, including at least two different means of loosening material, highly coordinated movements to manipulate material within their burrows and the ability to rotate up to 270 degrees while simultaneously excavating. The description presented here and further experiments using the techniques we have developed will likely lead to a new generation of bio-inspired robots that have multi-use parts that permit, not simply obstacle negotiation, but modification of the environment, thus permitting increased mobility in rough terrain and complex environments, such as collapsed buildings following a natural disaster.