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 (Ta). 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 Ta's and entered torpor. Instead, food deprivation led to selection of higher Ta's and slight lowering of body temperature (Tb), 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.