In the Kenyan savannah, an invasive ant species has caused an ecological chain reaction that is changing the prey patterns of lions. A tiny invader has reconfigured the dynamics between predator and prey, a research team writes in the journal Science. Instead of zebras, as before, the lions now more often hunt Cape buffalo, but they are much more difficult to overpower.
According to researchers led by Douglas Kamaru of the University of Wyoming, the chain reaction started like this: Alien big-headed ants (Pheidole megacephala) drove out native Crematogaster ants. These live in the thorns of whistling acacias (Vachellia drepanolobium) and act like bodyguards: if a herbivore dares to nibble on ‘their’ tree, they pounce on it within seconds and bite painfully. Even African elephants (Loxodonta africana) are deterred by it.
Local ants stabilized the trees
“To our great surprise, we found that these little ants are incredibly strong defenders and essentially stabilized the tree cover in these landscapes, allowing the acacia trees to survive in a place with so many large herbivorous mammals,” explains co-author Todd Palmer of the University of Florida. However, big-headed ants, believed to have originated from an island in the Indian Ocean, do not defend the trees.
Whistling acacias make up more than 70 to almost 100 percent of all woody trunks in the region, the study continues. Without the protective ants, elephants eat and break five to seven times more trees. This is where the lions come into play: they use the privacy of the acacia trees to stalk their favorite prey: plains zebras (Equus quagga). The simple equation: fewer trees means less hunting success. With the spread of big-headed ants, the number of zebras killed by lions has noticeably decreased, according to the research team.
“The world responds to the little things”
“We often find that it’s the little things that make the world go round,” says Palmer. “These little invasive ants appeared maybe fifteen years ago and none of us noticed because they are not aggressive towards large animals, including humans. Now we see them changing the landscape in very subtle ways, but with devastating consequences.”
The study authors report that the lion population has not yet declined. Presumably because they changed their diet from lots of zebras to more Cape buffalo (Syncerus caffer). However, these are larger and more difficult to catch. “Nature is smart and animals like lions tend to find solutions to the problems they face,” says Palmer. “But we don’t yet know what the outcome could be of this profound change in the lions’ hunting strategy.” It will be very interesting to follow the story further.
Source: Krone
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