Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Convergent acoustic field of view in echolocating bats

Abstract

Most echolocating bats exhibit a strong correlation between body size and the frequency of maximum energy in their echolocation calls (peak frequency), with smaller species using signals of higher frequency than larger ones1,2. Size–signal allometry or acoustic detection constraints imposed on wavelength by preferred prey size have been used to explain this relationship1,3. Here we propose the hypothesis that smaller bats emit higher frequencies to achieve directional sonar beams, and that variable beam width is critical for bats. Shorter wavelengths relative to the size of the emitter translate into more directional sound beams4. Therefore, bats that emit their calls through their mouths should show a relationship between mouth size and wavelength, driving smaller bats to signals of higher frequency. We found that in a flight room mimicking a closed habitat, six aerial hawking vespertilionid species (ranging in size from 4 to 21 g, ref. 5) produced sonar beams of extraordinarily similar shape and volume. Each species had a directivity index of 11 ± 1 dB (a half-amplitude angle of approximately 37°) and an on-axis sound level of 108 ± 4 dB sound pressure level referenced to 20 μPa root mean square at 10 cm. Thus all bats adapted their calls to achieve similar acoustic fields of view. We propose that the necessity for high directionality has been a key constraint on the evolution of echolocation, which explains the relationship between bat size and echolocation call frequency. Our results suggest that echolocation is a dynamic system that allows different species, regardless of their body size, to converge on optimal fields of view in response to habitat and task.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Sonar beam width decreases as emitter (bat) size increases relative to wavelength.
Figure 2: Vertical and horizontal directionality in six species of vespertilionid bats.
Figure 3: Directivity index for six species of vespertilionid bats with forearm lengths ranging from 32 to 54 mm.
Figure 4: Gape size estimated from skulls and from the piston model.

References

  1. 1

    Jones, G. Scaling of echolocation call parameters in bats. J. Exp. Biol. 202, 3359–3367 (1999)

    CAS  PubMed  Google Scholar 

  2. 2

    Barclay, R. M. R. & Brigham, R. M. Prey detection, dietary niche breadth, and body size in bats: why are aerial insectivorous bats so small? Am. Nat. 137, 693–703 (1991)

    Article  Google Scholar 

  3. 3

    Houston, R. D., Boonman, A. M. & Jones, G. Do echolocation signal parameters restrict bats' choice of prey? In Echolocation in Bats and Dolphins (eds Thomas, J. A., Moss, C. F. & Vater, M ) 339–345 (Chicago Univ. Press, 2004)

    Google Scholar 

  4. 4

    Mogensen, F. & Møhl, B. Sound radiation patterns in the frequency domain of cries from a vespertilionid bat. J. Comp. Physiol. 134, 165–171 (1979)

    Article  Google Scholar 

  5. 5

    Dietz, C., von Helversen, O. & Nill, D. Handbuch der Fledermäuse Europas und Nordwestafrikas: Biologie, Kennzeichen, Gefährdung 1st edn (Kosmos, 2007)

    Google Scholar 

  6. 6

    Bradbury, J. W. & Vehrencamp, S. L. Principles of Animal Communication 2nd edn (Sinauer Associates, 2011)

    Google Scholar 

  7. 7

    Suthers, R. A. Vocal mechanisms in birds and bats: a comparative view. An. Acad. Bras. Cienc. 76, 247–252 (2004)

    Article  Google Scholar 

  8. 8

    ANSI standard S1 Method for the Calculation of the Absorption of Sound by the Atmosphere. Report No. ANSI S1 26–1995 (ASA 113–1995) Acoustic. Soc. Am. (1995)

  9. 9

    Lawrence, B. D. & Simmons, J. A. Measurements of atmospheric attenuation at ultrasonic frequencies and the significance for echolocation by bats. J. Acoust. Soc. Am. 71, 585–590 (1982)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Pye, J. D. Is fidelity futile? The 'true' signal is illusory, especially with ultrasound. Bioacoustics 4, 271–286 (1993)

    Article  Google Scholar 

  11. 11

    Waters, D. A., Rydell, J. & Jones, G. Echolocation call design and limits on prey size: a case study using the aerial-hawking bat Nyctalus leisleri . Behav. Ecol. Sociobiol. 37, 321–328 (1995)

    Article  Google Scholar 

  12. 12

    Surlykke, A., Pedersen, S. B. & Jakobsen, L. Echolocating bats emit a highly directional sonar sound beam in the field. Proc. R. Soc. B 276, 853–860 (2009)

    Article  Google Scholar 

  13. 13

    Land, M. F. & Nilsson, D. E. Animal Eyes 2nd edn (Oxford Univ. Press, 2012)

    Book  Google Scholar 

  14. 14

    Ghose, K. & Moss, C. F. Steering by hearing: a bat's acoustic gaze is linked to its flight motor output by a delayed, adaptive linear law. J. Neurosci. 26, 1704–1710 (2006)

    CAS  Article  Google Scholar 

  15. 15

    Jakobsen, L. & Surlykke, A. Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit. Proc. Natl Acad. Sci. USA 107, 13930–13935 (2010)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Moss, C. F., Chiu, C. & Surlykke, A. Adaptive vocal behavior drives perception by echolocation in bats. Curr. Opin. Neurobiol. 21, 645–652 (2011)

    CAS  Article  Google Scholar 

  17. 17

    Schnitzler, H.-U. & Kalko, E. K. V. Echolocation by insect-eating bats. Bioscience 51, 557–569 (2001)

    Article  Google Scholar 

  18. 18

    Herring, S. W. & Herring, S. E. The superficial masseter and gape in mammals. Am. Nat. 108, 561–576 (1974)

    Article  Google Scholar 

  19. 19

    Kallen, F. C. & Gans, C. Mastication in little brown bat, Myotis lucifugus . J. Morphol. 136, 385–420 (1972)

    CAS  Article  Google Scholar 

  20. 20

    Purvis, A. & Rambaut, A. Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative data. Comp. Appl. Biosci. 11, 247–251 (1995)

    CAS  PubMed  Google Scholar 

  21. 21

    Norberg, U. M. & Rayner, J. M. V. Ecological morphology and flight in bats (Mammalia; Chiroptera): wing adaptations, flight performance, foraging strategy and echolocation. Phil. Trans. R. Soc. B 316, 335–427 (1987)

    ADS  Article  Google Scholar 

  22. 22

    Simmons, J. A., Fenton, M. B. & O'Farrell, M. J. Echolocation and pursuit of prey by bats. Science 203, 16–21 (1979)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Baagøe, H. J. in Recent Advances in the Study of Bats (eds Fenton, M. B., Racey, P. & Rayner, J. M. V. ) 57–74 (Cambridge Univ. Press, 1987)

    Google Scholar 

  24. 24

    Jones, G. & Teeling, E. C. The evolution of echolocation in bats. Trends Ecol. Evol. 21, 149–156 (2006)

    Article  Google Scholar 

  25. 25

    Wotton, J. M., Jenison, R. L. & Hartley, D. J. The combination of echolocation emission and ear reception enhances directional spectral cues of the big brown bat, Eptesicus fuscus . J. Acoust. Soc. Am. 101, 1723–1733 (1997)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Brüel & Kjær. Condenser Microphones and Microphone Preamplifiers for Acoustic Measurements. Data Handbook (Brüel & Kjær, 1982)

  27. 27

    Ruedi, M. & Mayer, F. Molecular systematics of bats of the genus Myotis (Vespertilionidae) suggests deterministic ecomorphological convergences. Mol. Phylogenet. Evol. 21, 436–448 (2001)

    CAS  Article  Google Scholar 

  28. 28

    Hoofer, S. R. & Van den Bussche, R. A. Molecular phylogenetics of the chiropteran family Vespertilionidae. Acta Chiropterol. 5, 1–63 (2003)

    Article  Google Scholar 

  29. 29

    Hulva, P., Horácek, I., Strelkov, P. P. & Benda, P. Molecular architecture of Pipistrellus pipistrellus/Pipistrellus pygmaeus complex (Chiroptera: Vespertilionidae): further cryptic species and Mediterranean origin of the divergence. Mol. Phylogenet. Evol. 32, 1023–1035 (2004)

    CAS  Article  Google Scholar 

Download references

Acknowledgements

We thank H. Baagøe and B. Fenton for access to the bat collections at the Natural History Museum of Denmark and the Royal Ontario Museum, respectively, and R. Fisher and J. Hallam for providing gape heights of bats in flight. S. Brinkløv, C. Elemans, B. Falk, B. Fenton, J. Galef, P. Madsen, C. Moss, H.-U. Schnitzler and M. Wahlberg provided detailed comments that improved the manuscript. This study was funded by the Danish Council for Natural Sciences (FNU), Carlsberg, Oticon and the European Commission via the Seventh Framework Programme project ChiRoPing, Information Society Technologies Contract 215370. Animal capture and experimentation was approved by Skov- og Naturstyrelsen (Denmark).

Author information

Affiliations

Authors

Contributions

L.J. was responsible for conducting the experiments and programming. All authors contributed to data analyses and the writing of the manuscript.

Corresponding author

Correspondence to Annemarie Surlykke.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains 2 Supplementary Tables and Figures. (PDF 1547 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Jakobsen, L., Ratcliffe, J. & Surlykke, A. Convergent acoustic field of view in echolocating bats. Nature 493, 93–96 (2013). https://doi.org/10.1038/nature11664

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing