Discover, cover, flee: The competitive value of Aphaenogaster tool-use

Link To Share This Poster: https://cdmcd.co/mXy88Y
Live Discussion Link: https://cdmcd.co/XGgwWd

Dylan Gladson and Paul Brunkow, Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL

Background/Question/Methods
Competition is a force that has helped shape diversity of morphology and behavior observed in animal species, and understanding mechanisms of competitive interactions can help clarify how subordinate species can coexist with competitive dominants. Aphaenogaster rudis is a forest-dwelling subordinate ant species frequently displaced at food sources by more aggressive ant species. A. rudis may alleviate this competition through use of a unique foraging behavior: at sites containing liquid food, A. rudis uses nearby debris, such as soil or leaf litter, to absorb and transport food back to the nest, a behavior widely accepted as an example of tool-use. Several authors propose that this makes liquid food less available to competitors. In addition, A. rudis exhibits extremely high food discovery ability. However, how A. rudis tool-use, discovery ability, and lack of food defense are intertwined has not been investigated. We observed foraging characteristics of A. rudis lab and field colonies when presented liquid food.
Results/Conclusions
In field trials, A. rudis workers discovered liquid bait stations 25% faster than did three other competing species. In lab trials, workers quickly dropped soil into liquid food, but average number of individuals decreased once harvesting of saturated soil began; harvest time also significantly decreased with increasing initial concentration of soil in the liquid food. Tool-use permits turning “immovable” food into movable food often before competing ants find it but also may function to make liquid food inaccessible to competing ants. This strategy may allow Aphaenogaster to devote workers toward continued searching and to reduce direct interaction with more aggressive competitors.