Magnetic alignment in mammals and other animals

Abstract

Magnetic alignment (MA) constitutes the simplest directional response to the geomagnetic field. In contrast to magnetic compass orientation, MA is not goal directed and represents a spontaneous, fixed directional response. Because animals tend to align their bodies along or perpendicular to the magnetic field lines, MA typically leads to bimodal or quadrimodal orientation, although there is also growing evidence for a fixed unimodal orientation not necessarily coinciding with the magnetic cardinal directions. MA has been demonstrated in diverse animals including insects, amphibians, fish, and mammals. Alignment can be expressed by animals during resting as well as on the move (e.g. while grazing, hunting, feeding, etc.). Here, we briefly survey characteristic features and classical examples of MA and review the current knowledge about the occurrence of MA in mammals. In addition, we summarize what is known about mechanisms underlying MA and discuss its prospective biological functions. Finally, we highlight some physiological effects of alignment along the magnetic field axes reported in humans. We argue that the phenomenon of MA adds a new paradigm that can be exploited for investigation of magnetoreception in mammals.