EU research shows magnetic fields, vibrations help ants navigate
Living in the barren environment of the desert, desert ants cannot rely on landmarks to find their way, but amazingly they never get lost. Scientists in Germany have discovered that as well as counting their steps, these incredible creatures also use ground vibrations and magnetic fields to return safely home after searching for food.
Previous research has shown that ants use path integration - whereby animals use cues to track distance and direction to estimate their geographical position - to find their way home. Researchers working at the Max Planck Institute for Chemical Ecology in Jena, Germany have now proved that desert ants can also use magnetic and vibrational landmarks to make their way back to their nest. The study is published in the journal PLoS ONE.
The European researchers said that while path integration is a 'fascinating mechanism that ants use for orientation'' and 'an important survival formula in the barren environments of deserts,' the method is 'error-prone'. Hence the added use of visual and olfactory landmarks as important cues. For ants, finding the right nest is a question of life and death as they may be killed or at least attacked by resident ants if they enter the wrong nest accidentally. The research team therefore wanted to test whether desert ants were also able to use magnetism and vibrational signals in the absence of other landmarks. 'We were very surprised that this is actually the case,' says PhD student Cornelia Buehlmann, who carried out the experiment.
To test the importance of magnetic and vibrational landmarks for the ants, Ms Buehlmann and her colleagues placed a channel near a nest entrance, and trained some ants to locate the bait. The channel contained either a magnetic, vibrational, visual or olfactory nest-defining landmark. They then compared the behaviour of these ants with that of a control group, who were trained to find the bait but whose channel contained no landmarks, and a group of naïve ants that experienced the landmark in the test situation for the first time.
The researchers found that both the control and the naïve ants used the path integration system to find their nest as expected and ignored any changes to the landmarks. However, the ants that were trained while their nests were paired with a landmark walked past where their nest would have been when changes to the landmark were made. They searched for their nest at the spot where the landmark had originally been placed and ignored the information from the path integration system.
Trained desert ants therefore pinpointed their nest without any problem if a battery-powered vibrational device was buried next to the nest entrance. However, to exclude any electromagnetic effects from the device, the researchers carried out experiments using the vibrational device without contact to the ground, and 'the ants behaved like their untrained conspecifics' and 'wandered around aimlessly.'
The experiments demonstrated that desert ants have 'highly sensitive reaction to vibrational signals,' say the researchers, but they admit that it was unclear which sense is involved when the ants orientate themselves using the artificial magnetic field around the nest.
'This doesn't mean that ants have a kind of sensory organ for the detection of magnetic fields,' said the institute's Dr Markus Knaden. 'Their behaviour could also be caused by abnormal neural electrical signals due to the strong magnetic field which were memorised by the ants.' But whatever the case, ants which have adapted to extremely inhospitable habitats seem to be remarkably flexible in terms of using all senses for navigation, the team concludes.
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Data Source Provider: Max Planck Institute for Chemical Ecology; PLoS ONE
Document Reference: Buehlmann, C., et al. (2012) 'Desert Ants Learn Vibration and Magnetic Landmarks', PLoS ONE 7, 3. DOI:10.1371/journal.pone.0033117
Subject Index: Earth Sciences