After the “snowball effect” and the “butterfly effect,” could there be an “ant effect”? In any case, researchers have just shown how the invasion of an invasive formicide species has disrupted the fragile savannah ecosystem and the eating habits of lions in Kenya.
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“We often find that the world is run by very small things that can have devastating effects that we did not expect,” emphasizes Todd Palmer, a professor at the University of Florida, one of the authors of this study published Thursday in the journal Science published study.
It all started 15 years ago on the vast plains of Laikipia, Kenya. The place is covered by whistling acacias, a type of tree around which a harmonious balance has been created between the different species.
A local ant built its nest there and in return became the protector of this tree. Despite its thorns, the acacia would otherwise be eaten by local herbivores, particularly elephants, which are repelled by the insect colony's pheromones and spines.
However, this beautiful collaboration was interrupted by the introduction of the big-headed ant, triggered by human activity, which quickly drove the other ants out of the acacia tree and left it vulnerable to pachyderms again.
The end of the surprise effect
At first, no one noticed the ants “because they are not aggressive toward large creatures, including humans,” Palmer notes. But “we now see that they are changing landscapes in very subtle ways, but with devastating effects.”
Previous studies have shown that the arrival of this invasive species resulted in five to seven times greater elephant damage to the region's acacia trees, further reducing forest cover.
However, the latter was also an essential element of the lions' hunting strategy, which, thanks to the foliage of the trees, was able to create an effect of surprise, essential for catching their favorite prey, the zebras.
AFP
The study, conducted over three years at Kenya's Ol Pejeta Conservancy, comparing areas where big-headed ants invaded with those where big-headed ants did not, shows that the arrival of big-headed ants led to three of the lions' fatal attacks the zebras.
Cascade effects
But far from reducing cat populations due to lack of food, they have, on the contrary, adapted by switching their prey to buffalo. The latter require more effort from the lions because they are more difficult to catch, but do not necessarily reduce their food ration.
In some ways, that's good news because lion populations have remained “stable, even after all the cascading effects that have occurred,” Douglas Kamaru, lead author of the study, told AFP.
But the “question is what happens in the future” if there is another upheaval, when the presence of lions in the region has declined sharply, from 100,000 to 2,000 individuals, and the change in diet of the kings of the savannah could also lead to one series of unexpected consequences.
Even if “nature is intelligent” and lions have found an effective adaptation strategy for the moment, large-headed ants in critical situations could also cause problems for other species that rely on the whistling acacia, such as giraffes or black rhinos, and are at risk of extinction, the underlines Study.
Aside from ants, these risks are proven. Last year, the Intergovernmental Scientific Advisory Group of the United Nations Convention on Biological Diversity (IPBES) listed more than 37,000 so-called alien species that have taken root far from their place of origin. Of these, 3,500 are considered invasive and cause great damage to biodiversity.