An invading ant creates chaos at a wildlife park in Kenya
Learning Objective: Students will explain how an invasive species has affected several native species in an ecosystem.
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
pawel.gaul/Getty Images (Acacia Tree); Nature Picture Library/Alamy Stock Photo (Wiped Out Tree)
Left: Acacia trees provided a home for acacia ants and shelter for many animals.
Right: Invading ants wiped out acacia ants, leaving acacia trees unprotected.
Ants Attack!
Courtesy of Todd Palmer
Ecologist Todd Palmer
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
He studies wildlife in East Africa.
For millions of years, these
Jim McMahon/MapMan®
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.
Lions Out of Luck
The invasion of big-headed ants changed much of the landscape from woodland to open grassland. This means bad news not only for the trees but also for the countless animals that use them for shelter—including lions.
Lions typically work in groups to take down animals bigger than they are. In East Africa, their favorite food is zebras. But zebras are alert and speedy. To get close enough to strike, lions usually hide behind acacia trees.
Palmer and his team wondered: With fewer trees, what are lions eating?
After tracking lionesses from five groups, the team found that hunger had driven Ol Pejeta’s lions to target a new prey. Instead of hunting mainly zebras, they stalked a more dangerous foe—brawny buffalo.
Buffaloes’ huge size and sharp horns make them risky to attack. Unlike zebras, which run away, buffalo lower their horns and fight back. But with less tree cover to help with hunting zebras, the lions had no choice.
Danita Delimont/Alamy Stock Photo
Lions changed hunting strategies, targeting dangerous buffalo.
Making Connections
What will happen to East Africa’s lions in the future? Scientists don’t know. They are developing plans to use chemicals called insecticides to kill off the invading ants. If successful, hopefully acacia ants and acacia trees would come back. But invasive animals tend to be difficult to get rid of.
What scientists do know is that this story of tiny ants affecting mighty lions shows how creatures are connected in unexpected ways.
“Our discovery was so surprising to me,” says Douglas Kamaru, an ecologist on the team. “You’re talking about an ant—something so small! Yet it is reorganizing a whole
1. PREPARE TO READ (10 minutes)
Activate prior knowledge and work together to define the vocabulary word ecosystem.
2. READ AND SYNTHESIZE (20 minutes)
Read the article and analyze visual and textual information.
3. RESPOND TO READING (15 minutes)
Interpret a map of big-headed ant sightings.
