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The Body Electric
blocked the sun's angle and polarized light, and with 1-gauss magnets
attached to their heads the birds couldn't find their way home. How-
ever, each avian Ulysses who wore the lenses but no magnets faultlessly
navigated the 150 miles southwest to Ithaca, then flew ever tighter cir-
cles around the loft and fluttered in like a helicopter to a perfect blind
landing.
Carrying the work forward after Keeton's untimely death soon after
this experiment, Charles Walcott and Robert Green of the State Univer-
sity of New York at Stony Brook, working with James L. Gould of
Princeton,
outfitted
pigeons
with miniaturized
electromagnetic
coils
that let the researchers vary the type and orientation of applied field at
will. They discovered that if the south pole of the field was directed up,
the birds could still find home, but with the north pole up they flew
directly away from it. That meant they were using magnetic north as a
reference point. At about the same time two German scientists, Martin
Lindauer and Herman Martin, analyzed half a million bee dances and
found a "magnetic error" in them—a compensation for the difference
between magnetic north and true north. They were also able to intro-
duce specific angles of error in the dances with specifically oriented coils
around the hive. Here was proof that magnetic guidance systems existed
in both the birds and the bees. * The next question was how the systems
worked.
In 1975 Richard P. Blakemore, then a graduate student at the Uni-
versity of Massachusetts in Amherst, astonished the world of biology
with the announcement that some bacteria, the lowliest of all cells, also
had a magnetic sense. Blakemore made the discovery when, studying the
salt marshes of Cape Cod, he noticed that one type of bacterium always
oriented itself north-south on his microscope slides. Soon he found mag-
netotactic bacteria (those reactive to magnetism) near Cambridge, Mas-
sachusetts, where he set about studying them with Richard Frankel of
MIT's magnet lab. The direction to magnetic north points through the
earth somewhat down from the horizon, and the scientists became con-
vinced that the bacteria were using the field to guide themselves ever
downward to the mud where they throve, since they were too small to
sink through the random molecular motion of the water around them.
* Recent work by Cornell biologist Kraig Adler showed that the magnetic sense of sala-
manders was many times more acute than even
even that of pigeons. Not only could
the
amphibians find home without tight or other common cues; in addition, when Adler
tried to confuse them with artificial fields, they quickly adapted to the interference and
oriented themselves correctly in relation to the weaker geomagnetic background.