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Body lift, drag and power are relatively higher in large-eared than in small-eared bat species

Hakansson, Jonas LU ; Jakobsen, Lasse LU ; Hedenström, Anders LU and Johansson, L. Christoffer LU (2017) In Journal of the Royal Society Interface 14(135).
Abstract

Bats navigate the dark using echolocation. Echolocation is enhanced by external ears, but external ears increase the projected frontal area and reduce the streamlining of the animal. External ears are thus expected to compromise flight efficiency, but research suggests that very large ears may mitigate the cost by producing aerodynamic lift. Here we compare quantitative aerodynamic measures of flight efficiency of two bat species, one large-eared (Plecotus auritus) and one small-eared (Glossophaga soricina), flying freely in a wind tunnel. We find that the body drag of both species is higher than previously assumed and that the large-eared species has a higher body drag coefficient, but also produces relatively more ear/body lift than... (More)

Bats navigate the dark using echolocation. Echolocation is enhanced by external ears, but external ears increase the projected frontal area and reduce the streamlining of the animal. External ears are thus expected to compromise flight efficiency, but research suggests that very large ears may mitigate the cost by producing aerodynamic lift. Here we compare quantitative aerodynamic measures of flight efficiency of two bat species, one large-eared (Plecotus auritus) and one small-eared (Glossophaga soricina), flying freely in a wind tunnel. We find that the body drag of both species is higher than previously assumed and that the large-eared species has a higher body drag coefficient, but also produces relatively more ear/body lift than the small-eared species, in line with prior studies on model bats. The measured aerodynamic power of P. auritus was higher than predicted from the aerodynamic model, while the small-eared species aligned with predictions. The relatively higher power of the large-eared species results in lower optimal flight speeds and our findings support the notion of a trade-off between the acoustic benefits of large external ears and aerodynamic performance. The result of this trade-off would be the ecomorphological correlation in bat flight, with large-eared bats generally adopting slow-flight feeding strategies.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aerodynamics, Bats, Body lift and drag, Ears, Flight, Power
in
Journal of the Royal Society Interface
volume
14
issue
135
publisher
Royal Society
external identifiers
  • scopus:85033215253
ISSN
1742-5689
DOI
10.1098/rsif.2017.0455
language
English
LU publication?
yes
id
03a6ec61-d8ef-4f90-83ea-ce41a3c26de0
date added to LUP
2017-11-16 08:54:39
date last changed
2018-01-07 12:25:54
@article{03a6ec61-d8ef-4f90-83ea-ce41a3c26de0,
  abstract     = {<p>Bats navigate the dark using echolocation. Echolocation is enhanced by external ears, but external ears increase the projected frontal area and reduce the streamlining of the animal. External ears are thus expected to compromise flight efficiency, but research suggests that very large ears may mitigate the cost by producing aerodynamic lift. Here we compare quantitative aerodynamic measures of flight efficiency of two bat species, one large-eared (Plecotus auritus) and one small-eared (Glossophaga soricina), flying freely in a wind tunnel. We find that the body drag of both species is higher than previously assumed and that the large-eared species has a higher body drag coefficient, but also produces relatively more ear/body lift than the small-eared species, in line with prior studies on model bats. The measured aerodynamic power of P. auritus was higher than predicted from the aerodynamic model, while the small-eared species aligned with predictions. The relatively higher power of the large-eared species results in lower optimal flight speeds and our findings support the notion of a trade-off between the acoustic benefits of large external ears and aerodynamic performance. The result of this trade-off would be the ecomorphological correlation in bat flight, with large-eared bats generally adopting slow-flight feeding strategies.</p>},
  articleno    = {20170455},
  author       = {Hakansson, Jonas and Jakobsen, Lasse and Hedenström, Anders and Johansson, L. Christoffer},
  issn         = {1742-5689},
  keyword      = {Aerodynamics,Bats,Body lift and drag,Ears,Flight,Power},
  language     = {eng},
  month        = {10},
  number       = {135},
  publisher    = {Royal Society},
  series       = {Journal of the Royal Society Interface},
  title        = {Body lift, drag and power are relatively higher in large-eared than in small-eared bat species},
  url          = {http://dx.doi.org/10.1098/rsif.2017.0455},
  volume       = {14},
  year         = {2017},
}