The mandibles of stag beetles have sensors that communicate which portions of the mandible are engaged and the stress that is applied. The stag beetle uses information from the sensors in the madibles to adjust the muscular force. The tips are often thinner than the base and the stress is greatest. If only the tips are engaged, the beetle applies less force to his mandibles than if the more robust mid section of the mandible is enaged. Thus, the beetle adjusts the muscular force on the madibles to balance the grip on the opponent with the need to avoid damage.
*J. Goyens, J. Soons, P. Aerts, J. Dirckx. Finite-element modelling reveals force modulation of jaw adductors in stag beetles. J. R. Soc. Interface 2014 11 2014 0908
DOI: 10.1098/rsif.2014.0908. Published 8 October 2014