"We conducted two key experiments," says Kathrin Steck, PhD student at the institute. "First we marked four odour sources surrounding the nest entrance with the substances methyl salicylate, decanal, nonanal, and indole, and got the ants trained on them. If these four odour points were shifted away from the nest in the original arrangement, the ants repeatedly headed for the odours, even though the nest wasn't there anymore. If we rearranged the odour 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 odour landscape to their nest. The odour landscape comprising the four substances was monitored with the help of a special measuring technique: the scientists used a specific photoionisation detector to determine the distribution of the odour substances in space and time.
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," Markus Knaden, the leader of the study, explains. In fact, ants with only one sensory device were unable to make use of the odour landscape for navigation.
Stereo smelling in animals is not new rats and humans are thought to have this ability as well. 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," says Bill Hansson, director at the institute. [JWK, AO]
|Contact: Bill S. Hansson|
Max Planck Institute for Chemical Ecology