In Africa, there are plants of all forms and sizes, and it has some amazing trees also. They form part of the stunning photographs you find coming out of trips to Africa into the bush at any time of the year. But that beautiful Acacia tree is actually a dangerous killer. Yes, this tree is not actually a harmless plant, when they are being threatened by too many herbivores then they fight back.
Capable of the killing of whole herds of antelopes and even warning other Acacia trees that dangerous is close and it is time to watch out. Giraffes have figured this out years ago, they nibble on Acacia trees and then move away upwind, and nibble on another. Never eating too much from one tree, even when there are many leaves left.
And it is a good thing that the giraffes did figure this out because they were not wrong: acacia trees have a lethal weapon. They can raise the level of tannin-c in their leaves when being eaten. It only takes an animal to start eating them eagerly and within 15 minutes the tree will have shoot up its tannin-c levels to lethal doses. Doses so high that antelopes cannot break it down in their stomach and end up perishing due to eating indigestible leaves.
This is how the acacia tree survives and makes sure they are never completely eaten. But it does not stop there, when one tree decides to defend itself then it lets others know! They release a molecule called ethylene into the air and this floats downwind to other trees. The whole forest then starts other producing tannin-c even if they had not been eaten yet.
One thing is sure when acacias are overeaten, this is a deadly consequence on the local antelope population. A true picture of mother nature and our eco-system: survival of the fittest.