Functional leg design in dung beetles: Morphological adaptations to food relocation behavior

Dung beetles are coprophagous insects that reproduce and feed on vertebrate faeces. The dependency on the same ephemeral food source leads to frequent contact between individuals and thus intense competition. As a consequence, different strategies of food relocation (horizontal and vertical) have evolved, that put different stresses on the functional morphology of the extremities depending on whether dung is rolled as a ball, carried in fragments or dragged directly into the underground burrow. Previous studies have indicated some very basic adaptations in size and shape of specific leg segments to those behaviors. However, the exact relationship between the leg morphology and the functionality for different food relocation techniques mainly remains unexplored to date and represents the aim of the present study. We therefore explore the leg functional morphology of three dung beetle species: Anoplotrupes stercorosus (Coleoptera: Geotrupidae), Scarabaeus (Kheper) lamarcki and Scarabaeus galenus (Coleoptera: Scarabaeidae). Our results reveal that there are strong differences in the opening angles of the leg joints as well as the orientation of the very basal coxa segment. Our findings thus reveal significant biomechanical adaptations in dung beetles, shedding light on how leg morphology correlates with food relocation strategies. Understanding these adaptations not only enhances our knowledge of dung beetle biology, but also provides new insights in the leg construction that may inspire bio-inspired robotics.