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Abstract

The desert ant Cataglyphis fortis inhabits the North African saltpans where it individually forages for dead arthropods. Homing
ants rely mainly on path integration, i.e., the processing of directional
information from a skylight compass and distance information
from an odometer. Due to the far-reaching foraging runs,
path integration is error-prone and guides the ants only to the
vicinity of the nest, where the ants then use learned visual and
olfactory cues to locate the inconspicuous nest entrance. The
learning of odors associated with the nest entrance is well established.
We furthermore know that foraging Cataglyphis use the
food-derived necromone linoleic acid to pinpoint dead insects.
Here we show that Cataglyphis in addition can learn the association
of a given odor with food. After experiencing food crumbs
that were spiked with an innately neutral odor, ants were strongly
attracted by the same odor during their next foraging journey. We
therefore explored the characteristics of the ants’ food-odor memory
and identified pronounced differences from their memory for
nest-associated odors. Nest odors are learned only after repeated
learning trials and become ignored as soon as the ants do not
experience them at the nest anymore. In contrast, ants learn food
odors after a single experience, remember at least 14 consecutively
learned food odors, and do so for the rest of their lives.
As an ant experiences many food items during its lifetime, but
only a single nest, differentially organized memories for both contexts
might be adaptive.