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, 10 (4), e0123205
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Bats Respond to Very Weak Magnetic Fields

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Bats Respond to Very Weak Magnetic Fields

Lan-Xiang Tian et al. PLoS One.

Abstract

How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae) can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 μT; the lowest field strength tested here), the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT), despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05). Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Angular histograms of roosting locations in the natural geomagnetic field (A) and a polarity reversed magnetic field (B).
Field intensity is 51μT. Black arrows indicate the direction and magnitude of the mean resultant vector. Nm: magnetic north.
Fig 2
Fig 2. Angular histograms of roosting locations in different magnetic field strengths and in reversed polarity at the weakest field strength.
(A) 1/3rd of natural field strength. (B) 1/4th of natural field strength. (C) 1/5th of natural field strength. (D) reversed polarity of a magnetic field with 1/5th of natural field strength. Nm: magnetic north.

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Cited by 4 PubMed Central articles

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Publication types

Grant support

This research was supported by Chinese Academy of Sciences Cross-disciplinary Collaborative Teams Program for Science, Technology and Innovation, the CAS project (KZCX2-YW-T10) and National Natural Science Foundation of China grants (41374074, 41330104).
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