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 (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.

Thermal energetics of bats of the family Vespertilionidae: an evolutionary approach

“…For instance, Bozinovic et al (2014) found that, for 85 species of rodents, the species inhabiting cold climates presented a wider TNZ b than those living in warm climates. Similarly, Medina-Bello et al (2023) found that individuals of the cave myotis ( M. velifer ) from a warm tropical dry forest had a narrower TNZ b than bats from a temperate forest. Although differences in climate affinity may explain the lack of relationship between M b and TNZ b , this topic needs further investigation.…”

“…We placed one empty chamber of the same size (410 mL) inside the cabinet to take simultaneous baseline measurements from the animal chamber every second. Because we did not have any system that allowed us to switch the airflow between the empty chamber and the animal’s chamber to the same respirometer, we followed the protocol used by Medina-Bello et al (2023) to take the baseline measurements in our experiments. In this methodology, the empty chamber was connected to a different respirometer of the same brand (FoxBox®, Sable Systems International, Las Vegas Nevada, U.S.A.) with the same type of sensors (O 2 fuel cell and CO 2 infra-red sensors) and the same flow rate as that of the experimental chamber.…”

“…Measurements at each T a were taken once the readings of the two gasses reached an asymptote, which was achieved once that the T a stabilized within the chamber (i.e., ± 0.5 ºC around the mean value of each experimental T a ). Measurements were done following Medina-Bello et al (2023). To do this, we placed each bat in a metabolic chamber (410 mL) inside a cabinet connected to a digital temperature controller (PELT5®; Sable Systems International, Las Vegas, USA).…”

The behavioural costs of overcrowding for gregarious cave‐dwelling bats

“…Most bat species have an optimal roost type and inter-individual spacing, which varies based on aggression, body size, air temperature, and other factors. Many species use darker spaces in the cave that are further from the entrance of the roost, and larger or more aggressive species may be more likely to have more space between individuals to reduce stress and the possibility of overheating (Medina-Bello et al, 2023;Rodrigues et al, 2003). Multiple variables can influence the well-being of roosting bats, including the structure of the roosts, the surrounding ecological conditions and anthropogenic interventions within cave ecosystems (Nagy & Postawa, 2011;Sedlock et al, 2014).…”