INTRO: Koalas are pretty darn cute, but...they aren’t the brightest bulb on the continent. They will only eat eucalyptus leaves off the branch [which are toxic and low in nutritious value]. On a plate, a koala won’t recognize their one and only food. Yet, somehow, koalas are still alive. And it's all thanks to some pretty clever adaptations.
Sounds like they’re doomed. Hundred years or so from now there’ll be a photo of last koala in captivity. One question, why hasn’t the eucalyptus evolved to deter koalas? Part of me thinks the tree derives some benefit from koala munching.
The eucalyptus toxicity was probably a defense mechanism, but koalas won that evolutionary arms race.
They also probably evolved to see food on the ground as inherently dangerous, due to exposure to predators.