Energy metabolism and body temperature in the Blue-naped Mousebird (Urocolius macrourus) during torpor

Mousebirds (Coliiformes) respond to cold exposure and food limitation with nightly bouts of torpor. During torpor, metabolic rate and body temperature decrease markedly, which results in energy savings. The decrease in body t emperature is a regulated phenomenon as is also the arousal which occurs sp ontaneously without external stimuli. During arousal, Blue-naped Mousebirds warm at a rate of 1 degrees C/min. This process requires significant amoun ts of energy. Our calculations show that the overall savings for the whole day are 30% at an ambient temperature of 15 degrees C when daylength is 10 hours. Using glucose assays and RQ measurements, we found that during fasti ng, the birds switch to non-carbohydrate metabolism at an early phase of th e day. This may be one of triggers eliciting torpor. By using cluster analy sis of glucose levels we could clearly divide the night phase into a period of effective energy saving (high glucose levels) and arousal (low glucose levels).