An ant invasion indirectly reduced the number of zebras preyed upon by lions.Credit: Lynne Smit
The presence of invasive ants in trees indirectly reduced the number of zebras preyed upon by lions, researchers observed in a study at a nature reserve in Kenya.
Published in Science, the study noted that the invasive big-headed ant species disrupted a relationship between native ants and the region’s thorny acacia trees that cover 40% of the Ol Pejeta reserve in southern Kenya. The native ants prevented grazing animals from eating the trees, and in their absence, elephants destroyed the trees at five to seven times the rate in areas where they were displaced by invasive ants.
This is because native ants form armies on the trees deterring elephants from feeding on the trees. The invasive big-headed ants numerically overwhelm and completely exterminate the natives, killing adult ants and consuming eggs, larvae, and pupae. They then leave the trees, thus offering no protection from herbivores.
“This led to a wider open landscape that reduced the hiding places for lions as they target their prey, and increased their visibility for zebras,” says Douglas Kamaru, the study’s lead author from University of Wyoming’s Department of Zoology and Physiology and Program in Ecology & Evolution, USA.
In areas not invaded by the big-headed ants, zebra kills were 2.87 times higher, and lions were forced to adapt their diets to include more African buffalo. The researchers say the study shows how disruption of a mutualism could have reverberations throughout an ecosystem.
“We never think about these animal interactions when we talk about conservation of ecosystems. Interactions of species can have far-reaching effects in an ecosystem,” Kamaru tells Nature Africa.
