Richard A. Holland a,1, Ivailo Borissov b,c, and Björn M. Siemers c
-Author Affiliations
aDepartment of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, 78315 Radolfzell, Germany;
bBulgarian Bat Research and Protection Group, National Museum of Natural History, 1000 Sofia, Bulgaria; and
cSensory Ecology Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
Edited by Thomas Kunz, Center for Ecology and Conservation Biology, Boston, MA, and accepted by the Editorial Board March 9, 2010 (received for review October 28, 2009)
Abstract
Recent evidence suggests that bats can detect the geomagnetic field, but the way in which this is used by them for navigation to a home roost remains unresolved. The geomagnetic field may be used by animals both to indicate direction and to locate position. In birds, directional information appears to be derived from an interaction of the magnetic field with either the sun or the stars, with some evidence suggesting that sunset/sunrise provides the primary directional reference by which a magnetic compass is calibrated daily. We demonstrate that homing greater mouse-eared bats (Myotis myotis) calibrate a magnetic compass with sunset cues by testing their homing response after exposure to an altered magnetic field at and after sunset. Magnetic manipulation at sunset resulted in a counterclockwise shift in orientation compared with controls, consistent with sunset calibration of the magnetic field, whereas magnetic manipulation after sunset resulted in no change in orientation. Unlike in birds, however, the pattern of polarization was not necessary for the calibration. For animals that occupy ecological niches where the sunset is rarely observed, this is a surprising finding. Yet it may indicate the primacy of the sun as an absolute geographical reference not only for birds but also within other vertebrate taxa.
navigation orientation sun compass Chiroptera sensory ecology
Footnotes
1To whom correspondence should be addressed. E-mail:rholland@orn.mpg.de.
Author contributions: R.A.H. and B.M.S. designed research; R.A.H., I.B., and B.M.S. performed research; R.A.H. and B.M.S. analyzed data; and R.A.H and B.M.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. T.K. is a guest editor invited by the Editorial Board.
+++++
PDF gratuito deste artigo aqui.
