Animal magnetism acts as 'internal compass' to help them navigate

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Washington, Feb 27 : Researchers at the Universities of Leeds and Princeton have found that animals have a magnetic mineral called magnetite in their bodies, which acts as an internal compass to help them find directions.

Dr Richard Holland from Leeds' Faculty of Biological Sciences and Professor Martin Wikelski from Princeton University conducted a study, where they examined the directions in which different groups of Big Brown bats flew after they were given different magnetic pulses and released 20km north of their home roost.

In a previous study, Dr Richard Holland and his colleagues found that bats used the Earth's magnetic field to get around, but until now, how bats were able to sense the field was still unknown.

Big Brown bats were put through a magnetic pulse 5000 times stronger than the Earth's magnetic field, but orientated the opposite way.

"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," Dr Holland said.

"By including this group, we could easily see if changes in behaviour were the result of confusion caused by the pulse itself rather the impact of its orientation on the magnetite," he added.

Both the control group and the bats subjected to a pulse orientated with the Earth's magnetic field made their way home as normal.

However, of those, which had been through the reverse direction pulse, only half followed the correct route home. The rest flew in the opposite direction.

"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," says Dr Holland.

"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."

The researchers conducted the study using radio transmitters on the bats, which were monitored from the ground, and from a plane to verify the signals were correct.

However, one drawback is that this kind of monitoring is limited to short distances, so now, the researchers are in talks with NASA and ESA about using satellites to help track smaller migratory birds and mammals.

The findings are published in the current issue of PLoS ONE.

ANI

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