Correlates of ball size and rolling speed in the dung beetle Kheper nigroaeneus (Coleoptera: Scarabaeidae)

Ball rolling in dung beetles is an energy expensive activity associated with elevated thoracic temperatures. The ability of individuals to engage in such energetically costly behaviour may be dependent on their body condition. Bilateral asymmetries arising from the interaction between an individual's genes and its environment have been hypothesized to reflect an organism's quality. A number of studies have shown that individuals with elevated levels of asymmetry perform less well under stress. We tested this hypothesis by measuring correlates of dung ball rolling speed in males and females of Kheper nigroaeneus (Coleoptera: Scarabaeidae). We found that larger beetles produced larger dung balls and rolled them faster along an experimental track. However, there was no relationship between ball rolling speed and the asymmetry of fore and hind tibia. There was also no relationship between the asymmetry of the beetle or the number of mites that it carried, and the level of mite infestation did not influence ball rolling speed.