They don't. That's how ZoSo got lost from his parents and ended up being raised by a tree-kangaroo.
While driving through the Australian outback, an russian tourist noticed a man at the side of the road having sex with a kangaroo.
A few miles further down the road, he came to a small dusty town.
So he parked his car, and went into the town pub for a drink.
He sat there enjoying a nice cold beer, and looking around the bar.
Suddenly, he noticed a one-legged man sitting over at a corner table, masturbating.
The russian tourist turned to the barman and said, "What kind of a country is this? A few miles down the road there was a guy having sex with a kangaroo, and now I see that guy in the corner masturbating in full view of everyone."
The barman said, "You heartless bastard! He's only got one leg. How do you expect him to ever catch a kangaroo?"