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Lions between flute acacia trees in the savannah: privacy protection for hunting

Photo: Victoria Zero

An invasion of ants has set off an ecological chain reaction in the Kenyan savannah. The intruder has had an impact on the lions' prey pattern, writes a research team in the specialist magazine "Science". Instead of zebras, as was previously the case, lions now more often hunt Cape buffalo, which are much more difficult to overpower.

Invasive species pose a significant threat to ecosystems. A recent report concluded that they are at least partially responsible for 60 percent of the global losses of animal and plant species. In few cases, exactly how unwanted invaders change the complex ecological relationships has been documented as precisely as in the current study.

Native ants protect the trees

According to researchers led by Douglas Kamaru from the University of Wyoming, the chain reaction in Kenya began like this: alien large-headed ants drove out native Crematogaster ants. These live in the thorns of flute acacias and behave like bodyguards: If a herbivore dares to nibble on the trees, they pounce on it within seconds and bite painfully. Even African elephants are deterred by this.

"To our surprise, we found that these little ants are incredibly strong defenders," said Todd Palmer of the University of Florida, co-author of the study. The animals stabilized the tree population in the savanna so that the acacia trees could survive in a place with many large herbivorous mammals. However, large-headed ants, which are believed to come from an island in the Indian Ocean, do not defend the trees.

Lions hunt fewer zebras

Flute acacias make up the majority of all woody trunks in the region, the study continues. If the protective ants are missing, elephants eat and break five to seven times more of the trees. Lions, in turn, use the acacia trees as a privacy screen to stalk their favorite prey, the plains zebras. Fewer trees mean less hunting success. With the spread of large-headed ants, the number of zebras killed by lions has dropped noticeably, according to the research team.

"We find that often the little things rule the world," said Palmer. »These tiny invasive ants appeared maybe 15 years ago and none of us noticed because they are not aggressive towards large animals, including humans. Now we see that they are changing landscapes in very subtle ways, but with devastating effects.”

The study authors report that the lion population has not yet decreased. Presumably because they partially changed their diet from zebra to Cape buffalo. However, Cape buffalo are larger and harder to capture. “We don’t yet know what could result from this profound change in the lions’ hunting strategy,” says Palmer.

msk/dpa