Male stag beetles fight each other over mating opportunities which has caused the enlargement and diversification of their mandibles through sexual selection. X-ray microcomputed tomography combined with iodine staining has proven to be a valuable technique to obtain the morphological data needed as input for mechanical finite element modeling in investigating the functional morphology of the stag beetle mandibles. Such models will enable the comparison of the maximal load of males and females and the investigation of morphological characteristics with a possible stress reducing effect.