Magnetic compass orientation in C57BL/6J mice.

We report evidence for a robust magnetic compass response in C57BL/6J mice. Mice were trained to build their nests in one of four magnetic directions by creating a light gradient along the long axis of a rectangular cage and positioning a nest box at the opposite (dark) end. The mice were then tested overnight in a circular, visually symmetrical arena in one of four magnetic field alignments. The positions of the nests built in the test arena showed strong unimodal orientation in the magnetic direction coinciding with the dark end of the training cage.