Why did koala numbers crash in Australia 100,000 years ago?

Koalas had to deal with a big change that made their numbers go down a long time ago.

Imagine you have your favorite snack every day, something like chocolate chips. But one day, the store runs out of chocolate chips and never brings more. That’s what happened to koalas 100,000 years ago.

Koalas eat eucalyptus leaves, which are kind of like their favorite snack, soft, tasty, and always there. But suddenly, something changed in the environment, and the eucalyptus trees started to be less common or not as good.

This was like if your favorite chocolate chip snack became harder to find. Koalas had to work harder to find food, and some didn’t survive because they couldn’t keep up with the change.

So just like you might eat fewer chocolate chips when they’re not around as much, koala numbers dropped because their favorite food wasn't available in the same way anymore.