Nature

Bats Detect Earth's Magnetic Field Using Magnetite!

But they seem to also have other mechanism

By Stefan Anitei, Science Editor

27th of February 2008, 08:59 GMT

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Bats exert a certain magnetism upon many nature lovers. But researchers from the Universities of Leeds and Princeton have found that they actually use electro-magnetism, due to an 'internal compass', enabling them to navigate; they tested Big Brown bats released 20 km (12 mi) north of their home roost and gave them different magnetic pulses.

Two years ago, the team from Leeds' Faculty of Biological Sciences found

that bats really used Earth's magnetic field for orientation, but the new study clearly establishes how this is done. Big Brown bats were placed in a coil (10 cm diameter by 10 cm long or 4 in x 4 in) with magnetic pulse 5,000 times more powerful than the Earth's magnetic field, but oppositely orientated. The coil produced a pulse of 0.4 seconds that was 0.1 tesla in strength.

"We had three groups of bats. One had undergone the magnetic pulse with a different orientation, and one control group had received no pulse at all. The third group had undergone the pulse, but in the same orientation as the Earth's magnetic field. By including this group, we could easily see if changes in behavior were the result of confusion caused by the pulse itself rather the impact of its orientation on the magnetite," said Dr. Richard Holland from Leeds' Faculty of Biological Sciences.

The control group went back to their roost place normally, and so did the group exposed to a pulse having the same orientation to the Earth's magnetic field. Of the bats exposed to a pulse with a different orientation, 50% flew home, while 50% flew in the opposite way.

"This clearly showed that it is the magnetite in their cells which give bats their direction as we were able to change how the bats used it as an internal compass, turning their north into south. But as only half were affected, it's likely there is another mechanism as well, which in some bats enabled them to override the impact of the pulse," said Holland.

Magnetite is encountered in the cells of many bird and mammal species, humans included, but modern humans cannot use it as an internal compass, even if it is possible that our ancestors could do it.

TAGS:

bat | magnet | pulse

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