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Desert Ant Uses Stereo Odor “Landscape” Detection in Navigation

The desert ant Cataglyphis fortis, which is native to the inhospitable salt-pans of Tunisia, is already well-known for its remarkable navigational abilities. It uses a sun compass along with a step counter and visible landmarks to locate its nest (a tiny hole in the desert ground) after foraging for food. Now, researchers at the Max-Planck Institute for Chemical Ecology in Germany have shown that these ants have another tool in their navigational toolbox. After the scientists recently discovered that these ants also use olfactory cues to pinpoint their nests, they conducted new experiments that revealed that the ants cannot only locate an odor source, but they also use the distribution of different odors in the vicinity of their nests in a map-like manner. The scientists found that the ants need both their antennae for this odor-guided navigation, that is, they smell the landscape scenery in stereo. "We conducted two key experiments," said Kathrin Steck, a Ph.D. student at the Institute. "First we marked four odor sources surrounding the nest entrance with the substances methyl salicylate, decanal, nonanal, and indole, and got the ants trained on them. If these four odor points were shifted away from the nest in the original arrangement, the ants repeatedly headed for the odors, even though the nest wasn't there anymore. If we rearranged the odor sources relative to each other, the ants were completely confused." Therefore the researchers assumed that ants do not "think" one-dimensionally--i.e., they do not associate the nest with only one smell--but multi-dimensionally, i.e., they relate an odor “landscape” to their nest. Spatial perception can easily be acquired if two separate sensory organs are available, such as two eyes for visual orientation. In the case of the ants, this would be their two antennae. "With this assumption, the second key experiment seemed obvious. We tested ants that only had one antenna," explained Dr. Markus Knaden, the leader of the study. In fact, ants with only one sensory device were unable to make use of the odor landscape for navigation. This new study shows that ants smell in stereo, but not only that. "In our experiments we demonstrated that ants successfully use stereo smelling for navigation in the desert," said Dr. Bill Hansson, senior author of the article. This new work is scheduled to be published in the journal Animal Behaviour. [Press release] [Animal Behaviour in-press abstract]