TAPACHULA, Mexico—Putting chunks of tuna on coffee plants is an unusual way to spend a morning in the mountains of southern Mexico. But it has been part of Senay Yitbarek’s daily routine for the past three summers.
Yitbarek uses the fish to attract ants – part of a research project to learn more about how biodiversity is maintained on an organic coffee farm here in southern Chiapas state, near the border with Guatemala.
“I’m fascinated with the question of how so many species can coexist,” said Yitbarek, a fifth-year doctoral student in ecology and evolutionary biology at the University of Michigan. “Where do the boundaries stop for one species before another species takes over?”
Every morning, Yitbarek puts on his knee pads so that he can crawl on the ground and observe the ants. He tucks his pant legs into his socks to keep the bugs from biting his legs. And he walks along the steep slippery slopes of coffee fields, trying not to fall on sharp little tree stumps that look like stakes that could easily pierce your gut.
The focus of his research is Wasmannia auropunctata, also known as the “little fire ant.” The reddish brown insects are tiny, about two millimeters long.
“We don’t know much about the ecology of this ant,” Yitbarek said.
Coffee farmers have a love-hate relationship with Wasmannia ants. On the positive side, the insects like to eat one of the biggest threats to the crop – the coffee berry borer, a tiny beetle that eats its way into coffee beans. The pest is the biggest insect threat to the coffee crop worldwide.
“Researchers have figured out that Wasmannia can get into the coffee berry and pick out the beetles,” Yitbarek said.
On the negative side, the feisty ants can attack coffee pickers, swarming over the workers’ necks and armpits, delivering a painful bite. This causes the workers to avoid plants infested with the ants, reducing the harvest.
Yitbarek hopes that by better understanding where the ants live, how they move around and get along with other species, farmers will be better able to manage their fields.