Differences in thermal energetics of the cave myotis (Myotis velifer) from a cool and a warm environment of central Mexico

Abstract

Endotherm homeotherms deal with the energetic cost of maintaining a stable body temperature ( Tb) in ecosystems differing in ambient temperature ( Ta). In response, animals adjust some of their thermal energetics to meet the energy requirements of thermoregulation. Bats are small mammals with a geographical distribution that may include environments with different Ta. Therefore, these animals should adjust their thermal energetics depending on the environmental characteristics of the habitats where they live. Using open-flow respirometry, we measured basal metabolic rate (BMR), thermal conductance ( C’), lower and upper critical temperatures ( TLC and TUC), and breadth of the thermoneutral zone (TNZb) of the cave myotis ( Myotis velifer (J.A. Allen, 1890)) living in a coniferous forest versus a tropical deciduous forest in central Mexico. To our knowledge, this is the first attempt to measure thermal energetics at the intraspecific level in populations measured at the same time. Bats from the coniferous forest had lower BMR, C’, TLC, TUC, and a wider TNZb than bats from the tropical deciduous forest. The results we found here are likely the consequence of the differences between the energy demands imposed by Ta, where the animals roost, and the Ta and prey availability of their foraging areas. These differences may help individuals regulate their heat production and dissipation to maintain low thermoregulatory costs in the places they inhabit.