How are Koalas alive? (arboreal survival)

[C C]

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.

https://www.youtube-nocookie.com/embed/BD6xtmH1r0M

[Zinjanthropos]

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.

[Syne]

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.