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 c attle farm located Northwest of Salamanca (Spain). Geotrupes mutator displa ys two well-defined and different thermoregulatory strategies throughout th e day. Only during a short and restricted daily period (110-0 lux of light intensity at dusk) does it abandon the thermoconformity state which predomi nates over the remainder of the day. This is only possible by endogenously increasing its body temperature above ambient temperature, allowing it to s hift from dung pad to dung pad by flying. It seems that the crepuscular fli ght activity and autumn-winter activity are only possible by means of endot hermic ability. Probably, flight activity at dusk has been selectively favo ured as a response to interespecific competition in dung and/or bird predat ion.