The poison is supposed to be so fast-working that the locals call it “Two Step” — because “you take two steps and drop dead” — but the lions died slowly.

Disorientated and vomiting, their vision blurring, the three lionesses and their eight cubs stumbled away from the poisoned carcass, breathing becoming ever harder until suffocation overtook them.

In just this single incident in April, more than a third of the famous tree-climbing lions in Uganda’s Queen Elizabeth National park were eliminated, leaving as few as 19 left in one of only two places in the world where lions display such arboreal behaviour.

The killing of lions in Africa is hardly new. Certain tribes, like the Maasai, have long hunted lions in coming-of-age rituals or to protect their livestock.

But as human populations have soared and the means of killing have grown more sophisticated, conservationists warn that Africa’s lions, like those that once roamed North America and Europe, could be driven to extinction.