Is torpor only an advantage? Effect of thermal environment on torpor use in the Siberian hamsters (Phodopus sungorus).

The aim of our study was determine torpor use in the Siberian hamsters (Phodopus sungorus) tested in a wide gradient of ambient temperatures (T(a)). Experiments were done on fed and food-deprived animals acclimated to winter-like and summer-like conditions. We found that neither fed nor unfed hamsters acclimated to winter-like or summer-like conditions selected low T(a)'s and entered torpor. Instead, food deprivation led to selection of higher T(a)'s and slight lowering of body temperature (T(b)), especially during the rest-phase of the day. Our calculations show that this strategy may lead to higher energy savings than torpor would. We argue that torpor use is not a fixed strategy but is determined primarily by a thermal conditions available in the environment.