By Dr. Becker
Humans have been collecting and planting seeds for 12,000 years, which sounds impressive until you hear that Fijian ants have us beat by a long shot; they’ve been farming for millions. Engaging in agricultural activities isn’t entirely unique among ants, as many ant species are known to do so. But the Fijian ants are unique in that they’re the only known animal-plant pair that depends on each other for survival.1
The plants in this case are Squamellaria, an epiphyte, or organism that grows on another plant. The ants are known to sow the seeds on trees with soft bark or nectar, such as the Macaranga tree. The ants plant the seeds in the tree bark’s cracks, then fertilize them via their own feces. As the plants mature and produce fruits, the seeds are harvested by the ants who continue to propagate the species.
Why are the ants so invested in this process? The plants form hollow structures called domatia that hang off the tree branches, which are the perfect place to call home. In addition to living in the plants’ hollows, they also eat the fruit of the plant. So far, it appears the ants choose to live in six varieties of Squamellaria plants. Study author Guillaume Chomicki of Ludwig-Maximilians-University of Munich told NPR, “I first noticed the relationship when I saw dozens of these ant-filled plants clustered in the same trees.”2
Fijian Ants Have a Mutually Dependent Relationship With Plants
The study, published in Nature Plants, represents the first time a mutually dependent relationship has been documented between ants and plants.3 The plants depend on the ants to plant their seeds and provide fertilizer, while the ants need the plants for shelter and food. Using genetic analysis, the researchers were even able to determine that Fijian ants (Philidris nagasau) lost the ability to build nests about 3 million years ago, which suggests this is around the time they decided living inside plants was preferable.
At this point in history, New Scientist reported, Fiji and Australia were still connected. Interestingly, in Australia, trees grow with similar Squamellaria plants on their branches as well, and ants are known to live inside them. It hasn’t yet been officially documented, but it’s likely the Australian ants are engaging in the same symbiotic relationship with the plants as the Fijian ants are.4
Kirsti Abbott, Ph.D., of the University of New England, Australia praised ants’ “sophisticated food production skills” and “impressive teamwork,” telling New Scientist:
“Ants are a lot smarter than we think they are — we call them superorganisms because they form networks that are much like our brains. The information flow among ant colonies is just insane compared to human social systems, so this finding does not surprise me in the slightest.”
Ants May Have Been Farming for 20 Million Years
It’s a humbling but true statistic: there’s evidence that ants may have been farming for 15 million to 20 million years. Acropyga ants live on tree roots underground and eat honeydew from mealybugs. The ants tend to their mealybugs much like humans tend to livestock, even carrying the bugs from root to root. When the ants move to a new colony, the queen carries a pregnant mealybug to the new location, basically starting a new “farm” to feed the colony.
Intriguingly, researchers have an idea of how long this has been going on because queen ants clutching pregnant mealybugs have been found in ancient fossilized amber.5 Perhaps more commonly known is the symbiotic relationship between ants and aphids.
Scientific American reported, “Aphids feed ants their excess sugars in the form of honeydew, and in return ants protect the aphids against predators and carry them to new host plants. The relationship forms a sort of miniature version of humans and their domesticated livestock.”6
Leafcutter ants are similarly impressive, cutting pieces of leaves from plants then carrying them underground into their nests and using them to grow fungus that serves as the colony’s primary food source. The behavior is incredibly complex, according to a study published in Royal Society Open Science, with the ants even selecting pieces of leaves that require less cutting in order to conserve energy.7
Also, it was found that 90 percent of the cutting takes place inside the nest, and it’s believed that young ants with the sharpest mandibles, used for cutting, may stay inside the nest for this purpose. Ants with worn mandibles, on the other hand, no longer cut leaves but instead perform the important task of carrying them.
It’s easy to view ants as pests, especially when they appear in unwanted places, like your kitchen. But the next time you see one, you might view it with a newfound respect. After all, as The New York Times put it, they figured out farming millions of years before humans.8