What are the most powerful animals on the African savanna? It’s hard not to think, “Lions, of course!” They can run as fast as a racehorse, 50 miles per hour (80 kilometers per hour). Their mighty jaws can kill prey in a single bite.

However, in one area of Kenya, the answer isn’t so simple. Lions there are experiencing a shake-up that’s changing how they hunt and what they eat. The cause? A creature smaller than a grain of rice: an ant.

This kind of ant, called the “big-headed ant,” is an invasive species. It’s rapidly spreading in a place it doesn’t belong. The ant has caused a chain reaction affecting an entire food web—including elephants, zebras, and lions. How could a tiny ant make problems for a lion? The story starts with a different ant and its special relationship with a tree.

What are the most powerful animals on the African savanna? It’s hard not to think, “Lions, of course!” They can run 50 miles per hour (80 kilometers per hour). That’s as fast as a racehorse. Their strong jaws can kill prey in a single bite.

However, the answer isn’t so simple in one area of Kenya. Lions there are facing a shake-up. It’s changing how they hunt and what they eat. The cause is an animal smaller than a grain of rice. It’s an insect called the “big-headed ant.”

This ant is an invasive species. It’s quickly spreading in a place it doesn’t belong. The ant is affecting an entire food web. It includes elephants, zebras, and lions. How could a tiny ant make problems for a lion? The story starts with another ant and its special relationship with a tree.

Acacia (uh-KAY-shuh) trees are common across East Africa. And usually, a hungry elephant knows to leave the trees alone. It probably learned this lesson the hard way! “Touch an acacia tree and hundreds of acacia ants will swarm and bite you where it hurts most, like the eyes, mouth, and underarms,” says ecologist Todd Palmer.
He studies wildlife in East Africa.

For millions of years, these native ants have had a special relationship with acacia trees that helps both survive. The trees provide a sugary nectar for the ants to eat. They grow special structures on their branches for the ants to live in. In return, the ants attack anything that tries to nibble on the trees.

Acacia (uh-KAY-shuh) trees are found across East Africa. A hungry elephant usually knows to leave the trees alone. It likely learned this lesson the hard way! “Touch an acacia tree and hundreds of acacia ants will swarm and bite you where it hurts most, like the eyes, mouth, and underarms,” says Todd Palmer. He’s an ecologist. He studies wildlife in East Africa.

These native ants have lived with acacia trees for millions of years. They help each other survive. The trees provide a sweet nectar for the ants to eat. The trees grow special structures on their branches. The ants live in them. The ants attack anything that tries to nibble on the trees in return.

About 15 years ago, Palmer and his team noticed a new kind of ant in a wildlife park called Ol Pejeta (ohl peh-JEH-tah) Conservancy. With massive heads compared with their smaller body size, their identity was no mystery. Big-headed ants had arrived!

Experts consider these ants among the world’s worst invasive species. Human activity, such as shipping goods and travel, has spread the critters from southeastern Africa around the globe. The ants clashed with the native acacia ants in Ol Pejeta. Palmer observed the big-headed ants climbing into acacia trees, eating the native acacia ants, and taking over the trees.

Unlike acacia ants, big-headed ants don’t protect the trees. With many of Ol Pejeta’s trees undefended, elephants ripped down acres of acacias. Now the landscape is dotted with bare stumps.

Palmer and his team noticed something about 15 years ago. It was a new kind of ant. It was in a wildlife park called Ol Pejeta (ohl peh-JEH-tah) Conservancy. The ants had heads much bigger than their bodies. That made their identity no mystery. Big-headed ants had arrived!

Experts view these ants as some of the world’s worst invasive species. The ants come from southeastern Africa. But they’re now found around the globe. Human activity, such as shipping goods and travel, has helped spread them. The ants clashed with the native acacia ants. Palmer saw the big-headed ants climbing into acacia trees. They’d eat the native acacia ants. Then they’d take over the trees.

Big-headed ants don’t protect the trees like acacia ants do. That’s left many trees without a way to defend themselves. So elephants ripped down acres of acacias. Now the landscape has bare stumps.