Male Participation in Nest Building in the Dung Beetle Scarabaeus catenatus (Coleoptera: Scarabaeidae): Mating Effort Versus Paternal Effort

The dung beetle, Scarabaeus catenatus, shows not only the rolling but also the tunneling tactic for nest building with bisexual cooperation. Sex roles, however, differed between the tactics. In rolling, the male took the initiative like that of ball-roller species: he rolled a dung ball away and buried it. In tunneling, in contrast, the male usually had a secondary role like that of tunnelers: he was less active in burrow excavation and provisioning. Regardless of the tactics, male participation did not increase female reproductive output measured by the number or size of brood balls in the field, but seemed to function as mate guarding against conspecific males. This suggests that, in both tactics, the male S. catenatus invests primarily in mating effort compared with paternal effort. The relative importance of mating effort in male participation seems to hold true in other dung beetles, irrespective of whether they are ball-roller or tunneler species. In addition, the male mating strategy of S. catenatus is compared with that of other ball-rollers.