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The Tunisian desert ant Cataglyphis fortis inhabits the hostile salt pans where it forages for dead arthropods. Some years ago we found that homing foragers locate their nest entrance by following a plume of carbon dioxide emanating from the nest entrance (Buehlmann et al. Current Biology 2012). Since this plume is not nest specific and ants are inevitably killed when they enter an alien nest, homing foragers only follow a plume when path integration, their main navigational tool, tells them that they are close to home. In addition, we have recently found that many foragers, although well adapted to their harsh environment, die from heat stress during foraging trips (Freire et al Current Biology 2023). Especially when returning from very long foraging trips, path integration is often not accurate enough to guide the ants directly back to the nest. The ants then begin a systematic search, which increases their chances of finding the nest entrance, but also exposes them further to the desert heat. Here we show that ants make a risk assessment during their search between being killed by the sun and being killed by an alien nest. Ants that have searched their nest for a while give up on safety and follow nest plumes even when the path integrator tells them that they may be far from home.
