Note from Con Slobodchikoff: This is a post by guest author Randall Johnson, who has contributed a number of posts and comments to this blog.
I remember growing up hearing and reading about the proverbial wisdom of ants. If you check the Old Testament, Proverbs 6:6-8 tell us: “Go to the ant, O sluggard; consider her ways, and be wise. Without having any chief, officer, or ruler, she prepares her bread in summer and gathers her food in harvest.”
And let’s not forget Aesop’s fable, “The Ant and Grasshopper”, which depicted the ant as a forward-thinking planner that gathered food in preparation for the coming winter while the grasshopper danced and played his fiddle, seemingly oblivious to future. This fable was, and still is, used to teach the virtues of hard work and saving and the perils of improvidence.
In the realm of ethology, ants have long been known for their complex cooperative behavior, including simple forms of rescue behavior, i.e., sand digging, which date back to 1874. [Belt T (1874) the Naturalist in Nicaragua. London: Murray].
Now, a new study, Nowbahari E, Scohier A, Durand J-L, Hollis KL (2009) Ants, Cataglyphis cursor, Use Precisely Directed Rescue Behavior to Free Entrapped Relatives. PLoS ONE 4(8): e6573. doi:10.1371/journal.pone.0006573, shows just how sophisticated this kind of behavior is.
In a total of 54 tests, the authors experimentally mimicked a natural situation involving an ant restrained by collapsing sand and debris. Hidden underneath the sand was a nylon snare that held the ant in place. If the captive ant was from a different colony or of a different species, the rescue ants ignored it. However, if the captive was a nestmate, the rescuers responded by excavating the sand, exposing the nylon thread, carrying sand away from the snare, and then biting at the snare itself.
These experiments demonstrated that the rescuers were somehow able to recognize what has holding their nestmate in place and direct approach behavior toward that specific object. This shows that rescue behavior is “far more exact, sophisticated, and complexly organized than previously observed,” unlike simpler actions such as digging and limb pulling, which could be triggered by a chemical distress signal.
The tests further showed that rescue behavior is directed exclusively toward a nestmate and it depends on an actively produced eliciting stimulus, most likely a pheromone that contains a component that is unique to each colony. However, pheromones alone don’t explain how the rescuers were able to find the precise location of the nylon thread and target their bites to the thread itself.
The authors distinguish rescue behavior from other types of cooperative acts in that the rescuing ants risk being trapped under the falling sand and there is no reward for the rescuers other than the benefits of kinship relationship.
Obviously, the ‘wise’ ant holds onto more secrets and surprises that might inspire new proverbs and fables.
Note: The PLoS ONE article includes two videos of these experiments.