What unique adaptations help koalas survive in its habitat?

Can't give the entire answer. One interesting facet of Koala's is that they are the only animal that appears to have a use for their appendix. Their appendix is significantly enlarged, allowing them to process cellulose more efficiently, thus being able to convert the leaves of various eucalypts into sugars which provide energy for living.

One reason the koala has a specific ecological niche is because there is almost no competition for the food in its niche. The niche of the koala is arboreal, and specifically, eucalyptus bushland. Besides the koala, only the Greater Glider and the Ringtail possum feed on eucalyptus leaves.