Acacia ants protect whistling-thorn trees by biting and stinging elephants looking for a snack. In return, they get nectar and shelter. But big-headed ants – an invasive ant species that can take over whistling-thorn trees by killing adult acacia ants and eating their eggs and larvae – offer no such protection.

“In invaded areas, elephants browse and break trees at five to seven times the rate of that in uninvaded areas,” Palmer and colleagues write in the journal Science.

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The team found that when big-headed ants and elephants were present there was a drop in tree cover and a dramatic increase in visibility.

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The team found zebra kills were almost three times more likely in low-visibility areas where big-headed ants were absent, than in high-visibility areas were the big-headed ants were present.

In short, acacia ants protect the trees in exchange for food, and the trees offer shelter for lions so they can hunt more easily. But invasive ants displace the acacia ants, leading to more trees dying, so lions have fewer places to hide when they hunt.