Sight, smell, touch, taste, hearing -- are these really all the senses animals possess? Rapidly accumulating evidence from creatures as diverse as bacteria and humans strongly implies the answer to be no. We all can sense Earth's magnetic field and use that information in ways of which people, at least, have scarcely been aware.
Magnetic material -- tiny bits of magnetite or lodestone -- have been found in bacteria, bees, pigeons, and dolphins. Many of these creatures have shown they use Earth's magnetism to help find their way around. Now Robin R. Baker and Janice G. Mather of the University of Manchester (England) report that European wood mice use an internal compass too.
This would be interesting in itself. But its overriding significance is the confirmation it gives of a similar sense in humans. Mammals, it suggests, do have a magnetic sixth sense. As Baker and Mather note in reporting their work in Nature, this is "the first evidence for such a sense in a mammal other than man." At this writing, it had yet to be demonstrated that dolphins actually use their magnetic material as part of a sense organ.
The mice, however, showed that they can maintain an accurate sense of home direction when carted away in boxes that prevent them from getting any clues from sight, smell, or hearing. Moreover, their directional sense can be confused if a spurious magnetic field is imposed while they are transported. "Wood mice do have a magnetic sense of direction," the two zoologists conclude.
These findings duplicate with mice what Baker has already found with people in a number of experiments carried out with Mather and other colleagues. Students, blindfolded and transported in buses, were found repeatedly to have A good sense of their direction from home base. This work must be considered preliminary, since other investigators have not yet been able to replicate these results with humans.
What may be more significant, Baker and Mather have evidence that a magnetic sense is important in everyday activities, not just in the contrived circumstances of navigational experiments. Their work with rodents led them to suspect this sense to be especially useful in exploring a new ground, acting to supplement the traditional five senses. They took students on a woodland walk in unfamiliar territory. All wore the magnetic helmets, but only some of these wre activated. Those students with activated helments lost their sense of direction, being disoriented with respect to their starting position.
Commenting on this, Baker has noted: "it shows that as we move around within our environment we make unknowing use of a magnetic sense. If a sense exists, presumably it also can be damaged." He urges research on "the impact of our environment on this previsouly unknown feature of our makeup" -- an environment increasingly "polluted" by electromagnetic radiation from radio radar, and televis ion.