Role of high body temperature in the endothermic dung beetle Geotrupes mutator (Coleoptera, Geotrupidae)

The thermal ecology of the dung beetle Geotrupes mutator was studied in a cattle farm located Northwest of Salamanca (Spain). Geotrupes mutator displays two well‐defined and different ther‐moregulatory strategies throughout the day. Only during a short and restricted daily period (110–0 lux of light intensity at dusk) does it abandon the thermoconformity state which predominates over the remainder of the day. This is only possible by endoge‐nously increasing its body temperature above ambient tempera ture, allowing it to shift from dung pad to dung pad by flying. It seems that the crepuscular flight activity and autumn‐winter activ ity are only possible by means of endothermic ability. Probably, flight activity at dusk has been selectively favoured as a response to interespecific competition in dung and/or bird predation.