The closest living relative of the koala is the wombat. Rather than climb trees, wombats are small burrowing marsupials that sometimes defend their burrows with their own bottoms. They can do so because they have no tail for a predator to grab and a bottom too hard to be bitten. If the intruder insists to chase it, the wombat might kick it with its hind legs and crush it against the ceiling of the burrow. Such a temper!