By Angie Rizzo
Small but Mighty
Tropical forests are full of interesting creatures, but (speaking from my own perspective, anyway) ants don’t usually come to mind as a particularly exciting tropical species. When it comes to ants, we often think of an annoyance to keep out of kitchens and homes, and it’s often our first instinct to kill an ant when we see it — perhaps worried about its bite, or just to get rid of one more picnic pest. While some of the over 12,000 ant species worldwide may fit that description, most of them are really incredible when you get a closer look at their life. In fact, after learning a bit more about their complex and specialized lives, Costa Rica’s leaf cutter ants have quickly become one of my personal favorite species.
There are about fifty known species of leaf cutter ants, and they are found primarily in the Neotropical region of Central and South America. Walking around Monteverde, especially in the trails of the forest, but sometimes even beside the road or even right behind the BEN office (where I’m watching a colony work tirelessly as I write about them), you’ll likely see small well worn paths full of little ants marching along, many carrying green leaf cuttings many times their own size. These are the leaf cutters, hard at work. Seeing this spectacle, you might assume that the ants are cutting and carrying leaves for food. In a way, this is true, but the ants don’t actually eat the leaves they go to such great lengths to collect. Instead, they bring the leaf cuttings back to the colony where they are fed to a fungus that the ants then eat. Harvesting this fungus, fending off disease, and maintaining a healthy colony is no small task, and the complexity and intricacy of how these ants operate is incredible.
Girl Power and Teamwork
Leaf cutters really understand teamwork – they have to work together to keep their fungus farms healthy and their colony alive and well. No one ant can do all of the tasks necessary to achieve a successful colony, so each ant has a specific role. The queen establishes a new colony and starts the fungus garden, and then has the sole role of laying eggs. Male ants have wings and fly between colonies to help queens reproduce. The rest of the ants are all infertile females that serve as workers, soldiers and guards. In fact, none of the ants you see trekking on well worn paths with leaf cuttings many times their own body weight are males, all of them are hard working women!
Farmers and Pharmacists of the Forest
The ants and the fungus have evolved the perfect mutualistic relationship where each benefits the other. The fungus is given food and protection from disease by the ants, and the ants are provided with food from the fungus that they cultivate. The ants secrete chemicals to help the fungus they feed on to grow, and they also produce bacteria that kills off parasitic fungus and other threatening diseases. We’ve learned a lot from these ants too, and use this same bacterium in many of our own pharmaceutical antibiotic drugs.
The ants also divide their colonies into distinct areas to keep the fungus and the ants healthy. Part of the colony is the farm, where ants bring leaf cuttings, chew them up a bit and “feed” the fungus. Younger workers tend to the farm areas, and older workers move on to the another part of the colony that serves as a dump. Here older ants finish out their final days, dying away from the healthier parts of the colony and keeping waste and harmful parasites contained.
Part of the Bigger Picture
While leaf cutter colonies are incredible ecosystems in their own right, they are also a part of the larger forest ecosystem and they play a key role in this bigger picture. Though ants are small, leaf cutters have been described as “the dominant herbivores of the New World tropics” (Britannica). Their habit of cutting leaves helps encourage plant growth, and their fungus farms enrich soil. Leaf cutter ants serve as a nice reminder that even seemingly small actions can lead to impressive results and teamwork can move mountains (and leaf piles). So next time you cross paths with an ant, think twice before squishing it – especially if it happens to be a leaf cutter!
References:
“Leafcutter Ant.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 17 Apr. 2017, www.britannica.com/animal/leafcutter-ant.
Fendt, Lindsay. “The Secret Lives of Leaf-Cutting Ants.” The Tico Times, 3 Apr. 2015, www.ticotimes.net/2015/04/03/the-secret-lives-of-leaf-cutting-ants.
Simões-Gomes, Flávia Carolina, et al. “Geographical Distribution Patterns and Niche Modeling of the Iconic Leafcutter Ant Acromyrmex Striatus (Hymenoptera: Formicidae).” Journal of Insect Science, vol. 17, no. 2, 1 Mar. 2017, www.ncbi.nlm.nih.gov/pmc/articles/PMC5416825/.
Angie Rizzo successfully completed an internship with the MCL and Children’s Eternal Rainforest from June to August 2018. She is a student at Lehigh University.