Torpor energetics are related to the interaction between body mass and climate in bats of the family Vespertilionidae

Torpor is an adaptive strategy that allows animals to cope with energy limitations under adverse environmental conditions. In birds and mammals, intrinsic and extrinsic factors such as body mass ( M b ) and ambient temperature ( T a ) are well established triggers of torpor. Interestingly, the interplay between M b and climate with different T a on torpor traits in bats remains unexplored. Using open flow respirometry, we calculated T a upon entering torpor ( T a t ), the reduction in torpid metabolic rate relative to the basal metabolic rate ( TMR red ), the T a at which torpor metabolic rate reached its minimum ( T a adjust ), and minimum torpid metabolic rate ( TMR min ) in 11 bat species of the family Vespertilionidae that differ in M b from warm and cold climates. We also included TMR min data retrieved through a bibliography review. We tested the effects of M b and climate on torpor traits using mixed-effect phylogenetic models. All models showed a significant interaction between M b and climate. This interaction was inversely related to T a t , TMR red , T a adjust , and positively related to TMR min . These results are likely explained by the differences in M b and the metabolic rate of bats from different climates, which may allow individuals to express torpor in places with different T a . Further studies to assess torpor use in bats of different climates are proposed. Summary statement The interaction between body mass and climate influences torpor energetics in bats of the family Vespertilionidae. As a result, torpid traits change based on body mass and climate.