How a tiny invasive ant changed the landscape and diet of lions in a Kenyan reserve

Imagine you are a buffalo and you live your quiet life in a reserve in Kenya, where the lions leave you alone because they are too busy hunting zebras. But one day things change and hunters start attacking their group in the open spaces that the elephants have left in their path: suddenly the zebras live happily and the buffaloes run away and are killed by the cats. And now imagine that this revolutionary change in your life as a giant herbivorous creature is blamed on an insignificant ant.

This little drama is not a script for a sequel to “The Lion King,” but a curious process that has been documented by a team of researchers led by Douglas Kamaru of the University of Wyoming, whose work is published this Thursday. magazine Science, The authors have carefully monitored the behavior and relationships between different animals and plants living in the Ol Pejeta Reserve in Kenya, and have shown that there has been the emergence of a small invader, known as the “African big-headed ant”. Is.Pheidole megacephala), have changed the landscape and modified the relationship between lions and their prey.

a series of changes

How did you do it? Scientists believe that it all started thanks to humans around the year 2000 with the arrival of this ant, which lives in other places in Africa but is not endemic to Laikipia, the area where the reserve is located. At this location, another species of large ants, belonging to the genus crematorium, lives in a mutualistic relationship with the thorny acacia of the Savanna. A cooperation that is very convenient for both species: the acacias provide nectar to the ants and the ants, with the painful sting of their stingers, protect the trees from elephants. But when “big-headed ants” enter and destroy the colonies crematoriumThe trees are left unprotected and the pachyderms destroy them until the land is cleared.

In this new, much more open landscape, lions can no longer sit among the acacias to hunt zebras as they always did, and are forced to seek alternatives in their daily diet. It is here that the buffalo family living peacefully becomes victim of unexpected incidents. According to data collected by Kamaru and his team, from 2003 to 2020, the proportion of zebras captured by lions in areas invaded by ants fell from 67% to 42%, while the proportion of buffalo killed increased from 0%. It became 42%. The end of a long chain of causes and effects that have changed the ecosystem.

When we started the study we predicted that with fewer zebras, the lion population would decline. the result was surprising

“This result is impressive and was very surprising to me,” Camaru explains to elDiario.es, “because when we thought about doing the study we predicted that, because there were fewer zebras, the lion population was going to be smaller. ” However, something happened that they did not expect and that was that it remained stable. “That led to another question, and then we started looking at what other things they were eating,” he says. “And to our surprise, they were beginning to hunt buffalo.” In subsequent measurements, they also verified that in the areas where there were ants, six groups of 66 adult lions that they tracked using GPS killed about three times fewer zebras than in the area where they Had not attacked yet.

join the dotted line

The idea to investigate these relationships came to Kumaru himself when, while studying the growth of lion populations in Kenya, he came across another study that described the effect of ant invasions on acacia trees. then it connected dotted line And started asking himself some questions. To answer them rigorously, he and his team had to sharpen their ingenuity and design a series of experiments that, in the first step, involved dividing the land into several plots of 2,500 square metres, restricting the herbivores’ access. To stop involved demarcating and being situated upon. Both sides of the ‘attack front’.

Comparing plots that were invaded by “big-headed ants” with plots that were not invaded, scientists found that the invasion made the trees more vulnerable to damage by elephants. “What surprised me in that scenario was the level of damage caused by these animals,” recalls Kamaru. “An area that was previously full of acacia was suddenly devastated and 70 to 80% of the trees disappeared.” Alejandro Pietrek, a CONICET researcher who designed some of the experiments in the plots, was most impressed by the corpses of native ant colonies piled up under each acacia tree after the invasion. “The natives are very big and strong, but bigheads They work in groups like a super colony; It is very impressive to see how they do not leave any other ants behind,” he explains.

For Kamaru, this result provides a lesson in the importance of studying interactions that go unnoticed in ecosystems. “Something as inconsequential as ants can affect an entire chain,” he says. “We must study them more and now the question is to find out what are the possible ways to eliminate them as they expand.” and are affecting other systems.” “Our study shows that a small invasive species, like this ant, can have large-scale impacts on the savanna and affect the way lions hunt,” says Pietrek. “And that the cascade of effects from one small invader can be huge.” Or, as Todd Palmer, an ecologist at the University of Florida and co-author of the article, says, it’s a sample of how “these little invaders are pulling at the threads that bind African ecosystems together and determining how , invisible, who is eaten and where.” ,

Our study shows how a small invasive species like this ant can have a large-scale impact and affect the way lions hunt.

The next step is to try to understand what other impacts these ants are causing in the environment and in other areas of the region that they have not yet investigated. “These ants are on multiple continents, and that means they’re probably causing more damage that we don’t know about; “Those are the questions we want to answer,” says Kamaru. As for the possibility of their eradication, they study what types of pesticides or biological agents might stop them, but must exercise extreme caution and attention. Keep that any small modification to the environment can lead to a series of unexpected consequences, as their study shows. On the other hand, Pietrek points out, it is much more difficult to stop an invasive species that comes with men from advancing. “We are everywhere and, even if we remove some of the focus, in an area where tourism exists, it is clear that the ants will arrive at another time.”

The case of the “crazy ants”

Elena Angulo, a researcher at the Doñana Biological Station (EBD-CSIC), who specializes in invasive ants, believes that this is a relevant study that goes a little further than what is known so far about the importance of ants in the conservation of trees. Is. Of the African Savanna. “And this teaches us that the impacts of invasive species may not be as obvious as they seem or may be hidden, and that is why they should be studied,” he explains.

On Christmas Island, crazy ants attacked and destroyed the native crab population, changing the composition of the soil and ultimately the rainforest.

The researchers recall other examples in which invasive ants have caused major changes to ecosystems, particularly on islands. “A very visible case is that of Christmas Island (Christmas Island), a remote island in the Indian Ocean with fauna and flora that has not been disturbed for millions of years,” he detailed. “‘Crazy ant’ accidentally arrives after human settlement (Enopolepis gracilipes)A very aggressive invader that attacked and destroyed native crab populations, altering the soil and ultimately the structure of the tropical forest.

Jose Manuel Vidal-CorderoAn entomologist specializing in ants at EBD-CSIC believes the article is “a tremendous example” to once again illustrate how these insects “shape ecosystems and direct the evolution of many organisms.” with whom they share residence.” And remember that the African big-headed ant is considered one of the 100 worst invasive species causing devastating problems worldwide. for its part, miguel claveroAn expert in biological invasions and Fellow at EBD-CSIC, believes this work highlights the importance of insects in ecosystems, and he small lifeIt is the basis of everything else, including microbials. “And what big impacts these small changes have, which if well described, as is the case, opens our eyes,” he emphasizes.

The red crab in the Guadalquivir Swamp in Doñana is one such case, where a species comes in and changes everything

This case reminds Clavero of the cascade of effects that began in 1970 on the west coast of North America, when Pacific otters were reintroduced, reducing sea urchin populations and resulting in the (in this case positive) proliferation of kelp forests. Happened. Or the famous case of Yellowstone wolves, which upon returning to their habitat caused great changes in the behavior of herbivores, vegetation and even the flow of rivers, although in this case part of the food chain downstream.

“We studied the case of the red crab in the Guadalquivir swamp in Doñana, which is a case of a species that has been introduced and changes everything,” reports Clavero. This tiny crustacean has completely changed the food chain, and “a place with clear water that was dominated by diving birds that ate vegetation and amphibians has become a place full of dirty water and herons,” he said. telling. A spectacular change that is very close to us and which, in the opinion of scientists, reminds us that we have to be alert, considering how many changes a single species introduced by us can generate in ecosystems.