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Published February 27, 2008 | Published
Journal Article Open

Bats Use Magnetite to Detect the Earth's Magnetic Field


While the role of magnetic cues for compass orientation has been confirmed in numerous animals, the mechanism of detection is still debated. Two hypotheses have been proposed, one based on a light dependent mechanism, apparently used by birds and another based on a "compass organelle" containing the iron oxide particles magnetite (Fe3O4). Bats have recently been shown to use magnetic cues for compass orientation but the method by which they detect the Earth's magnetic field remains unknown. Here we use the classic "Kalmijn-Blakemore" pulse re-magnetization experiment, whereby the polarity of cellular magnetite is reversed. The results demonstrate that the big brown bat Eptesicus fuscus uses single domain magnetite to detect the Earths magnetic field and the response indicates a polarity based receptor. Polarity detection is a prerequisite for the use of magnetite as a compass and suggests that big brown bats use magnetite to detect the magnetic field as a compass. Our results indicate the possibility that sensory cells in bats contain freely rotating magnetite particles, which appears not to be the case in birds. It is crucial that the ultrastructure of the magnetite containing magnetoreceptors is described for our understanding of magnetoreception in animals.

Additional Information

© 2008 Holland et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: October 19, 2007; Accepted: January 29, 2008; Published: February 27, 2008. Alison Cameron, Axel Haenssen, Nathan Gregory and A. Catherine Markham provided assistance in the field. Kasper Thorup and Wolfgang Wiltschko provided statistical advice. Kasper Thorup assisted with figure production. Author Contributions: Conceived and designed the experiments: MW RH JK. Performed the experiments: MW RH TD. Analyzed the data: RH. Contributed reagents/materials/analysis tools: MW RH JK. Wrote the paper: MW RH JK TD. Funding: Richard Holland was funded by a Marie Curie Outgoing international fellowship and a Bat Conservation international grant. Martin Wikelski was funded by the National Geographic society and NSF. None of these funding bodies had any influence on the manuscript. Competing interests: The authors have declared that no competing interests exist.

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