Caves, crevices and cooling capacity: Roost microclimate predicts heat tolerance in bats

Zenon J. Czenze, Ben Smit, Barry van Jaarsveld, Marc T. Freeman, Andrew E. McKechnie

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The microsites that animals occupy during the rest phase of their circadian activity cycle influence their physiology and behaviour, but relatively few studies have examined correlations between interspecific variation in thermal physiology and roost microclimate. Among bats, there is some evidence that species exposed to high roost temperatures (Troost) possess greater heat tolerance and evaporative cooling capacity, but the small number of species for which both thermal physiology and roost microclimate data exist mean that the generality of this pattern remains unclear. Here, we test the hypothesis that bat heat tolerance and evaporative cooling capacity have co-evolved with roost preferences. We predicted that species occupying roosts poorly buffered from high outside environmental temperature exhibit higher heat tolerance and evaporative cooling capacity compared to species inhabiting buffered roosts in which Troost remains well below outside conditions. We used flow-through respirometry to investigate thermoregulation at air temperatures (Ta) approaching and exceeding normothermic body temperature (Tb) among six species with broadly similar body mass but differing in roost microclimate (hot vs. cool roosts). We combined these data with empirical measurements of Troost for each study population. Hot-roosting species tolerated Ta ~4°C higher than cool-roosting bats before the onset of loss of coordinated locomotion and non-regulated hyperthermia. The evaporative scope (i.e. ratio of maximum evaporative water loss [EWL] to minimum thermoneutral EWL) of hot-roosting species (16.1 ± 2.4) was substantially higher than that of cool-roosting species (5.9 ± 2.4). Maximum evaporative cooling capacities (i.e. evaporative heat loss/metabolic heat production) of hot-roosting species were >2, while the corresponding values for cool-roosting species were ≤1. The greater heat tolerance and higher evaporative cooling capacity of hot-roosting species compared with those occupying cooler roosts reveal variation in bat evaporative cooling capacity correlated with roost microclimate, supporting the hypothesis that thermal physiology has co-evolved with roost preference. A free Plain Language Summary can be found within the Supporting Information of this article.

Original languageEnglish
Pages (from-to)38-50
Number of pages13
JournalFunctional Ecology
Volume36
Issue number1
DOIs
Publication statusPublished - Jan 2022
Externally publishedYes

Bibliographical note

Funding Information:
We are grateful to P. Pattinson for accommodation in Harrismith, K. Schoeman and Department of Zoology and Entomology Rhodents for essential field assistance. We also thank three anonymous reviewers for insightful and constructive comments that greatly improved the quality of the manuscript. This work was approved by the Animal Ethics Committee of the University of Pretoria (NAS171/2019 and NAS342/2019) and the Research and Scientific Ethics Committee of the South African National Biodiversity Institute (P19‐26 and P19‐19). This work is based on research supported by National Research Foundation of South Africa (grant 119754) to A.E.M. Any opinions, findings and conclusions or recommendations expressed in this article are those of the authors and do not necessarily reflect the views of the National Research Foundation.

Funding Information:
We are grateful to P. Pattinson for accommodation in Harrismith, K. Schoeman and Department of Zoology and Entomology Rhodents for essential field assistance. We also thank three anonymous reviewers for insightful and constructive comments that greatly improved the quality of the manuscript. This work was approved by the Animal Ethics Committee of the University of Pretoria (NAS171/2019 and NAS342/2019) and the Research and Scientific Ethics Committee of the South African National Biodiversity Institute (P19-26 and P19-19). This work is based on research supported by National Research Foundation of South Africa (grant 119754) to A.E.M. Any opinions, findings and conclusions or recommendations expressed in this article are those of the authors and do not necessarily reflect the views of the National Research Foundation.

Publisher Copyright:
© 2021 British Ecological Society

Keywords

  • bats
  • body temperature
  • evaporative water loss
  • heat tolerance
  • resting metabolic rate
  • roostmicroclimate
  • Bats
  • Resting metabolic rate
  • Body temperature
  • Heat tolerance
  • Roost microclimate
  • Evaporative water loss

Fingerprint

Dive into the research topics of 'Caves, crevices and cooling capacity: Roost microclimate predicts heat tolerance in bats'. Together they form a unique fingerprint.

Cite this