A non-invasive method for quantifying patterns of torpor and activity under semi-natural conditions

Understanding thermal biology in heterothermic endotherms requires that we accurately quantify temporal patterns of torpor use and activity. In many studies this is done using open-flow respirometry or implanted temperature sensitive transmitters. Here we report a method to quantify torpor and activity in cavity living endotherms that does not require surgery or confinement in metabolic chambers. We used temperature dataloggers affixed inside nests to record nest temperatures (Tnest) as a proxy for body temperature. We constructed nests so that animals were in direct contact with dataloggers while at rest. Passive infrared motion detectors were used to determine when animals were active in their cages outside nests. We confirmed that the approach accurately quantifies torpor patterns using open-flow respirometry. This method may prove useful in studies addressing temporal patterns of torpor use under semi-natural conditions because it results in little disruption to animals.