Ants are usually underrated due to their tiny size, but they can cause significant changes in the ecosystem, as their population is much more than humans and other animals on this planet. New research conducted by Kenyan researchers based on the impact of invasive ant species in Kenya helped determine their role in shaping the interaction between zebras and lions.
On 25 January 2024, an article was published in Science about the impact of tiny invasive big-headed ants on zebra kills by lions in Kenya, as these killed native acacia ants responsible for maintaining tree cover. Invasive attacks led to reduced tree cover and improved visibility of lions to zebras from a distance, which helped them avoid lion attacks.
The introduction of invasive ants in Kenya is good for the native zebras, but local lions, buffaloes, and native acacia ants are not happy due to significant disturbance after the invasion. However, it is interesting to know about the impact of invasion on the native flora and fauna of this country.
Ant-plant mutualism plays a crucial role in a lion’s life
A species of acacia ants (Crematogaster mimosae) is mutually associated with whistling-thorn trees in the forests and builds a positive relationship with them.
These protect plants from damage caused by herbivorous organisms and get shelter and food from them. They stop elephants and other animals from eating the leaves or other plant parts.
They all run toward branches after detecting vibrations around trees and inflict painful bites on the mouths or trunks of elephants, so they have to turn their backs to avoid the bites.
These ants are small but play a crucial role in maintaining tree cover despite the presence of plant-eating mammals in the landscape that are much bigger than them.
The tree cover helps lions hunt prey with remarkable efficiency and success because these ambush predators sit and wait to get closer to their prey.
Moreover, they stay in concealment and capture their prey suddenly so that it does not get a chance to escape. So, the mutualistic association between ants and plants is indirectly good for lions.
Impact of big-headed ants on acacia tree ants
A few researchers from the University of Wyoming, the University of Florida, and the University of Nairobi or other institutes studied the impact of big-headed ants on the population of acacia tree ants.
These big-headed ants (Pheidole megacephala) are invasive and wipe out the population of native insects due to their omnivorous diet. They eat plants, insects, and even insects of the same types.
Moreover, they are voracious predators that are commonly present in the Indian Ocean Island but have been found in Kenya for the past 20 years.
They invaded Laikipia County in Kenya and contributed to the ecosystem by changing the food chains or webs.
These invasive ants are not beneficial for native acacia ants because they attack trees and kill the adult ones and their eggs, larvae, or pupa.
Additionally, they are indirectly harmful to acacia trees because they kill the protectors of trees and make them prone to attack by herbivores.
Accordingly, the invasive species transformed landscapes silently because they had not caused harm to native larger animals, but their long-term effect is devastating due to landscape damage.
How did tiny invasive ants stop lions from killing zebra in Kenya?
A student of the University of Wyoming and some other researchers from institutes in Kenya or a few people from the OI Pejeta Conservancy Kenya studied the role of invasive ants on zebra kills.
It seems odd to know that tiny ants stopped lions from killing prey, but they can indeed reduce the preying potential of lions and save the lives of zebras.
These researchers investigated the invaded and non-invaded areas and compared the rate of killing of zebras, which was higher in the non-invaded region and led to further investigations to determine the reason.
They found that big-headed ants removed acacia tree ants by killing their colonies, which were beneficial for trees in terms of protection against herbivores.
This way, elephants started feeding on the plants in the big-headed ants-invaded regions and caused damage to the tree cover and landscapes.
Due to less tree cover, lions, the skilled predators, lost their ability to kill zebras without getting noticed, as they usually attack by hiding and patiently waiting for their prey.
Zebras can run at a speed of 45 to 55 mph, which is almost equal to that of lions, which is approximately 50 to 65mph, which means they can give their predators a tough time.
However, they fall prey to lions because these ambush predators stalk their prey and pounce upon them when the distance is too short to escape.
The invasion of big-headed ants in Laikipia County appeared as a blessing or lifesaver for zebras because they could see their predators from a distance due to their good vision.
They can detect movement at a distance of a few miles and run away without getting closer to the lions, so these invasive ants reduced zebra kills in that region.
Switching of lion’s diet after the invasion of big-headed ants
Significant changes in the lion’s diet occurred due to the invasion of big-headed ants because these tiny insects improved the visibility of predators to zebras.
Accordingly, these predatory animals switched their diet from zebras to African buffaloes to ensure survival. It was easy to hunt buffaloes due to their heavy and larger bodies.
Moreover, the rate of successful predation is higher because buffaloes usually forage and navigate in groups, so lions can capture one out of a large group.
A noticeable difference in the hunting behavior of lions has been observed in Kenya within the past several years, as the rate of zebra kills reduced from 67% to 42%.
However, a significant reduction is noticed in the population of buffaloes over many years because the percentage of lions hunting slow-moving buffaloes changed from 0% to 42%.
So, it has been found that these tiny invasive ants are responsible for dramatic changes in the local food chain in Kenya, and these are also responsible for the decreased population of native insects.