Biomechanics and strategies of digging

Abstract

In arid and semiarid ecosystems, digging and burrowing are common behaviors in many mammals looking for shelter, food, thermoregulation, etc. Many rodents, as tuco-tucos, may use both the foreclaws and incisors - according to soil requirements - to accomplish that goal in an effective manner. Although digging represents a low fraction of the daily energy budget, it triggered some highly derived adaptations. Forelimbs in caviomorph scratch-diggers are characterized by highly robust humeri and ulnae, and well-developed bony superstructures. These mechanically advantageous traits have been already found during early ontogeny in Ctenomys -compensating the lower muscular development - and encompass the gradual improvement of digging and burrowing behaviors on those stages. This fact would provide enough time to reach a proper musculoskeletal and behavioral development, to deal with energetic and biomechanical demands. Gross head morphology, instead, has proven to conserve a rodent already-optimized bauplan among caviomorphs, by not showing a more mechanically advantageous masticatory apparatus in tuco-tucos. Their strong bite forces-which cover both tooth-digging and a wide range of social needs- would be a consequence of the hypertrophied and fiber types-wise specialized jaw adduct musculature. Despite corresponding soil reaction forces may injure animal` s skull or teeth, ctenomyid skull geometry, bone distribution, and incisors microstructure evolved to withstand the high stress and abrasion. Thus, yet inconclusively, animal´ s performance can be fairly predicted based on biomechanics.