Is Hyperthermia a Constraint on the Diurnal Activity of Bats?

J. R. Speakman, G. C. Hays, P. I. Webb

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Bats are normally nocturnal, despite some potential advantages of being active during the day. A possible constraint on diurnal activity is hyperthermia. We evaluated the hyperthermia hypothesis by constructing a biophysical model which considered all the heat fluxes across a bat’s wing during diurnal flight and predicted a critical ambient air temperature T(acrit) above which a bat would be unable to fly without experiencing fatal hyperthermia: Many factors had important influences on T(acrit), including time of day, latitude, cloud cover and foliage cover. Ground surface temperature and ground albedo had significant but mutually opposed effects. Important organismal factors included body mass (larger bats were more susceptible to overheating), aspect ratio (lower aspect ratios more susceptible), flight speed (slower more susceptible), and the albedo and transmittance of the wing membranes (darker more susceptible). Using the expected latitudinal variation in the environmental components we suggest hyperthermia will constrain the diurnal flight of large bats (c. 900 g) at about 85% of sites between 40°S and 40°N. For intermediate sized bats (90 g) hyperthermia will constrain diurnal activity at 50-60% of sites between 20 and 30°N and CS but is less important around the equator (constrained at only 10% of sites). For small bats (9 g) hyperthermia will constrain diurnal activity at about 30-40% of sites between 20 and 30°N and °S, but less than 1% of sites at the equator. For all sizes of bats hyperthermia probably constrains flight in the day at less than 1% of sites above 50°N or °S.

Original languageEnglish
Pages (from-to)325-339
Number of pages15
JournalJournal of Theoretical Biology
Volume171
Issue number3
DOIs
Publication statusPublished - 7 Dec 1994

Fingerprint

Hyperthermia
diurnal activity
fever
Chiroptera
Aspect ratio
Fever
Heat flux
flight
Equator
Membranes
Temperature
Aspect Ratio
Air
Cover
Transmittance
transmittance
Heat Flux
surface temperature
Membrane
ambient temperature

ASJC Scopus subject areas

  • Statistics and Probability
  • Modelling and Simulation
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Agricultural and Biological Sciences(all)
  • Applied Mathematics

Cite this

Is Hyperthermia a Constraint on the Diurnal Activity of Bats? / Speakman, J. R.; Hays, G. C.; Webb, P. I.

In: Journal of Theoretical Biology, Vol. 171, No. 3, 07.12.1994, p. 325-339.

Research output: Contribution to journalArticle

Speakman, J. R. ; Hays, G. C. ; Webb, P. I. / Is Hyperthermia a Constraint on the Diurnal Activity of Bats?. In: Journal of Theoretical Biology. 1994 ; Vol. 171, No. 3. pp. 325-339.
@article{7655715fc9c64fb0be15ecc4e6d0b50e,
title = "Is Hyperthermia a Constraint on the Diurnal Activity of Bats?",
abstract = "Bats are normally nocturnal, despite some potential advantages of being active during the day. A possible constraint on diurnal activity is hyperthermia. We evaluated the hyperthermia hypothesis by constructing a biophysical model which considered all the heat fluxes across a bat’s wing during diurnal flight and predicted a critical ambient air temperature T(acrit) above which a bat would be unable to fly without experiencing fatal hyperthermia: Many factors had important influences on T(acrit), including time of day, latitude, cloud cover and foliage cover. Ground surface temperature and ground albedo had significant but mutually opposed effects. Important organismal factors included body mass (larger bats were more susceptible to overheating), aspect ratio (lower aspect ratios more susceptible), flight speed (slower more susceptible), and the albedo and transmittance of the wing membranes (darker more susceptible). Using the expected latitudinal variation in the environmental components we suggest hyperthermia will constrain the diurnal flight of large bats (c. 900 g) at about 85{\%} of sites between 40°S and 40°N. For intermediate sized bats (90 g) hyperthermia will constrain diurnal activity at 50-60{\%} of sites between 20 and 30°N and CS but is less important around the equator (constrained at only 10{\%} of sites). For small bats (9 g) hyperthermia will constrain diurnal activity at about 30-40{\%} of sites between 20 and 30°N and °S, but less than 1{\%} of sites at the equator. For all sizes of bats hyperthermia probably constrains flight in the day at less than 1{\%} of sites above 50°N or °S.",
author = "Speakman, {J. R.} and Hays, {G. C.} and Webb, {P. I.}",
year = "1994",
month = "12",
day = "7",
doi = "10.1006/jtbi.1994.1235",
language = "English",
volume = "171",
pages = "325--339",
journal = "Journal of Theoretical Biology",
issn = "0022-5193",
publisher = "Academic Press Inc.",
number = "3",

}

TY - JOUR

T1 - Is Hyperthermia a Constraint on the Diurnal Activity of Bats?

AU - Speakman, J. R.

AU - Hays, G. C.

AU - Webb, P. I.

PY - 1994/12/7

Y1 - 1994/12/7

N2 - Bats are normally nocturnal, despite some potential advantages of being active during the day. A possible constraint on diurnal activity is hyperthermia. We evaluated the hyperthermia hypothesis by constructing a biophysical model which considered all the heat fluxes across a bat’s wing during diurnal flight and predicted a critical ambient air temperature T(acrit) above which a bat would be unable to fly without experiencing fatal hyperthermia: Many factors had important influences on T(acrit), including time of day, latitude, cloud cover and foliage cover. Ground surface temperature and ground albedo had significant but mutually opposed effects. Important organismal factors included body mass (larger bats were more susceptible to overheating), aspect ratio (lower aspect ratios more susceptible), flight speed (slower more susceptible), and the albedo and transmittance of the wing membranes (darker more susceptible). Using the expected latitudinal variation in the environmental components we suggest hyperthermia will constrain the diurnal flight of large bats (c. 900 g) at about 85% of sites between 40°S and 40°N. For intermediate sized bats (90 g) hyperthermia will constrain diurnal activity at 50-60% of sites between 20 and 30°N and CS but is less important around the equator (constrained at only 10% of sites). For small bats (9 g) hyperthermia will constrain diurnal activity at about 30-40% of sites between 20 and 30°N and °S, but less than 1% of sites at the equator. For all sizes of bats hyperthermia probably constrains flight in the day at less than 1% of sites above 50°N or °S.

AB - Bats are normally nocturnal, despite some potential advantages of being active during the day. A possible constraint on diurnal activity is hyperthermia. We evaluated the hyperthermia hypothesis by constructing a biophysical model which considered all the heat fluxes across a bat’s wing during diurnal flight and predicted a critical ambient air temperature T(acrit) above which a bat would be unable to fly without experiencing fatal hyperthermia: Many factors had important influences on T(acrit), including time of day, latitude, cloud cover and foliage cover. Ground surface temperature and ground albedo had significant but mutually opposed effects. Important organismal factors included body mass (larger bats were more susceptible to overheating), aspect ratio (lower aspect ratios more susceptible), flight speed (slower more susceptible), and the albedo and transmittance of the wing membranes (darker more susceptible). Using the expected latitudinal variation in the environmental components we suggest hyperthermia will constrain the diurnal flight of large bats (c. 900 g) at about 85% of sites between 40°S and 40°N. For intermediate sized bats (90 g) hyperthermia will constrain diurnal activity at 50-60% of sites between 20 and 30°N and CS but is less important around the equator (constrained at only 10% of sites). For small bats (9 g) hyperthermia will constrain diurnal activity at about 30-40% of sites between 20 and 30°N and °S, but less than 1% of sites at the equator. For all sizes of bats hyperthermia probably constrains flight in the day at less than 1% of sites above 50°N or °S.

UR - http://www.scopus.com/inward/record.url?scp=0028585941&partnerID=8YFLogxK

U2 - 10.1006/jtbi.1994.1235

DO - 10.1006/jtbi.1994.1235

M3 - Article

AN - SCOPUS:0028585941

VL - 171

SP - 325

EP - 339

JO - Journal of Theoretical Biology

JF - Journal of Theoretical Biology

SN - 0022-5193

IS - 3

ER -