A team of researchers has discovered that a species of desert ant can recognise food odours for the duration of its life – a valuable skill when living in a challenging environment.
Pest managers will be aware that trail pheromones are key to the foraging success of ants. However, have you ever wondered how ants find food sources initially and decide which food to select? Certainly there is a random element in their foraging, but food odour also plays a role, and indeed ants can display long term memory of food odours. In fact, researchers from the Max Planck Institute for Chemical Ecology have demonstrated that desert ants (Cataglyphis fortis) can remember food odours for the duration of their lives, even after just one exposure!1
The desert ant lives in the harsh North African desert. It has been a species subject to extensive research due to its navigation skills – how do foragers find their way back to the nest (a hole in the ground), in such a featureless environment? Whilst researching the role of nest odours on their navigational abilities (it plays a crucial role), researchers noticed the ants learned food odours remarkably quickly.
In trials where they associated a variety of different odours with a food source, the researchers established that the ants could remember at least 14 consecutively learned food odours, and then recall these odours for the rest of their lives. The average life span of the desert ant is around six days (they readily fall victim to predators), and the odour memory was retained by at least 45% of foragers after 26 days. Impressive though this is, leaf-cutting ants remember information about the plants in their foraging areas that are deleterious to their symbiotic fungus for up to 18 weeks.2
From an evolutionary point of view, the ability to recognise and remember food odours associated with a beneficial food source allows for more efficient foraging. Even if the odour only travels a metre or two, food location become less random and exploitation of food sources can be achieved more quickly, vital in areas where food availability can be transient and there can be significant competition for these food sources.
From a pest manager’s point of view, the important take away is that ants do remember odours and food sources and this memory can last for a significant period of time. Although this study focused on positive association (the odours were associated with a beneficial food source), the ability to remember odours of harmful food sources is arguably more important, as feeding on a deleterious food source can mean the death of the colony.
This can potentially be important when using ant baits, especially if insufficient bait is used. If ants do not take sufficient bait to the nest and fail to feed the bait to all other nest members before it starts to cause an ill effect, there is always a chance that they will associate the ill effect with some odour aspect of the bait and learn to avoid the bait on subsequent presentations.
More information on ants.
1 Huber, R. and Knaden. M. (2018). Desert ants possess distinct memories for food and nest odors. Proceedings of the National Academy of Sciences, 2018.
2 Saverschek, N, et al (2010). Avoiding plants unsuitable for the symbiotic fungus: learning and long-term memory in leaf-cutting ants. Anim. Behav. 79, 689-698.
NB: Main image shows Cataglyphis bicolor, another desert ant belonging to the same genus as Cataglyphis fortis.