New research has shown that invasive big-headed ants have cost lions their favourite zebra prey at Ol Pejeta by reducing predators’ tree cover.
The lions hid under the trees and ambushed the zebras.
Now they have switched to buffalo, which require more predators and more work.
The study showed that the invasive insects kill native acacia ants that protect the whistling-thorn trees by emitting formic acid that repels elephants. The result is less tree cover for lions to ambush zebras.
The researchers said whistling-thorn trees, the dominant tree species in much of East Africa, provide nectar and shelter for native ants in a symbiotic relationship.
Without the native ants for defence, the thorn trees are devastated by elephants. The ants had stabilised the savannah tree cover across entire landscapes.
The research showed that a tiny invader reconfigured predator-prey dynamics among iconic species.
This news of the invasive species was reported in the journal Science and Newswise website.
The research was led by Douglas Kamaru, a University of Wyoming graduate student. He is part of Professor Jacob Goheen’s research group in the UW Department of Zoology and Physiology.
Kamaru said the good news is the lion population hasn’t declined since the insect invasion, because lions have switched from zebras to African buffalo, which are equally at risk of lion predation in invaded areas.
They said researchers said over the past two decades, invasion of the big-headed ant has disrupted the symbiotic relationship between whistling-thorn trees and native ants.
The researchers found that the big-headed ant invasion indeed reduced the zebra kills by lions by increasing the open landscape.
“The spread of the big-headed ant, one of the globe’s most widespread and ecologically impactful invaders, has sparked an ecological chain reaction that reduces the success by which lions can hunt their primary prey,” the researchers wrote.
The scientists say the Ol Pejeta Conservancy lions have maintained their numbers by killing more African buffalo, which are larger and more difficult to kill than zebras.
Elsewhere in East Africa, larger groups of lions are required to kill buffalo, which may eventually lead to changes in the size and composition of lion prides at the Ol Pejeta Conservancy.
“Although the invasion of big-headed ants has shaped the spatial distribution of zebra kills, and the frequency of zebra kills has declined over time.
“Prey switching by lions to more formidable prey seems to have thus far prevented any cascading effects on lion numbers,” the research showed.
They added that the role of behavioural adjustments in underlying the population stability of lions, plus the degree to which such stability can be maintained as big-headed ants advance across the landscape, remain open questions for future investigation.
Other members of the research team are from the Nature Conservancy, Universities of British Columbia, Florida, Nairobi, Duke, Glasgow, Karatina, Nevada-Reno and the US Geological Survey.
