The arrival of a tiny ant to a Kenyan wildlife preserve has made ripples in the food chain, all the way up to the mighty lion's eating habits. In just two decades, this invasive insect changed the ecosystem there, ultimately making it harder for lions to hunt. While this interaction between big and small could be right out of a fable, it's actually from a recent paper in the journal Science. Big-headed ants (scientifically known as Pheidole megacephala) are wiping out a native ant species, acacia ants, that have a mutualistic relationship with the whistling-thorn trees they inhabit, the Guardian reports. As the new ants in town form supercolonies that devour the eggs and larvae of the acacia ants, the trees become more vulnerable to large leaf-eaters, like elephants.
This is because Acacia ants attack elephants by swarming up their trunks and stinging them with a caustic chemical when they get within trampling distance of the trees, according to New Atlas. If you're wondering what this has to do with lions, that comes next. Big-headed ants don't have the same fervor for protecting whistling-thorn trees, so now they're on the decline (per NPR, 70-80% have been cleared by leaf-eaters stomping them in the last 20 years). Lions, which are ambush predators, typically use those trees for cover when they hunt fast animals, like zebras. And with less foliage to hide in wait, zebras become harder to catch, so the lions have largely switched to hunting down water buffalo.
"Because lions need cover to successfully stalk and ambush their prey, they are more exposed when there are fewer trees to hunker down behind, which seems to make it harder for them to successfully take down the zebra," says Todd Palmer, one of the paper's authors. From 2003 to 2020, zebra deaths by lions dropped from 67% to 42%, as the number of water buffaloes killed by them rose from 0% to 42%, per New Atlas. So far, this change hasn't affected the lion population, though water buffaloes are more dangerous prey for them to conquer. But witnessing the chain reaction the big-headed ants started has opened a fascinating window for scientists.
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"These tiny invaders are cryptically pulling on the ties that bind an African ecosystem together, determining who is eaten and where," says Palmer, per Science Daily. To track how the ants have influenced lion behavior, Palmer and his team relied on 30 years' worth of research using hidden camera traps, satellites monitoring collared lions, and computer modeling. As the big-headed ants continue to encroach on the protected area, the researchers plan to observe how lions fare, but also learn what it means for animals like the endangered black rhino that need whistle-thorn trees to survive. Palmer says they have begun recommending a few ways to protect the trees, including "temporarily fencing out large herbivores, to minimize the impact of ant invaders on tree populations." (An invasive, cannibalistic tree frog made its way to new US state.)
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