Magnets in Ant Antennae Work as Internal GPS

May 20, 2009 -- Miniscule magnets found in ant antennae could help to explain why these insects seem to always know where they are going, according to researchers who suspect the magnets are a key component of a sophisticated, nature-made GPS system.

Watch the ants raid a termite stronghold in this video.

While human global positioning systems rely upon power-consuming receivers that pick up information from clunky, orbiting 3,000-4,000-pound satellites, the probable ant system weighs next to nothing, requires little body energy to operate and is Earth-friendly to the max.

The system, in fact, appears to be mostly built out of dirt.

"The ants we studied dwell in tropical soils that are full of very fine-grained iron minerals, so there is plenty of material available," said researcher Jandira Ferreira de Oliveira of the Technical University of Munich and the Brazilian Center for Physics Research.

"The incorporation of minerals probably starts as soon as ants start getting in touch with soil," she added, explaining to Discovery News that her team found ultra fine-grained crystals of magnetic magnetite, maghemite, hematite, goethite, and aluminum silicates in ant antennae. These particles could make a "biological compass needle" that drives ant GPS.

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For the study, published in the latest Journal of the Royal Society Interface, Oliveira and her colleagues collected worker ants from the species Pachycondyla marginata in Sao Paulo. Prior studies found these ants tend to always migrate at an orientation of 13 degrees relative to Earth's geomagnetic north-south axis, and that the ant's strongest magnetic signal comes from its antennae.

High-powered microscopes and chemical analysis revealed the presence of the dirt-acquired magnetic particles in the antennae, intriguingly next to a body part called the Johnston's organ that may also be part of the ant's GPS.

Oliveira explained how the system might work.

Our planet is magnetized, likely due to rotational forces of liquid iron in Earth's core. Although the resulting magnetic field is one-twenty thousandth as strong as a refrigerator magnet, ants appear to "perceive the geomagnetic information through a magnetic sensor (the dirt particles), transduce it in a signal to the nervous system and then to the brain," she said.

Not all ants may use this particular system. Desert ants, for example, appear to have evolved special eyes that detect skylight polarization, which they then use to find their way around their sandy habitat. Magnetic particles, however, have been detected in many fish, birds, butterflies, flies, bees, bats, mole rats, newts, sea turtles and spiny lobsters, suggesting these animals find their way like the Brazilian ants do.