Why do kangaroos stand up on the their feet and fight with there hands?

That's really a bit of a fallacy; although they will occasioly spar like this, if they really want to do some damage thay balance on the base of the tail and use the large claw on their hindfeet to kick or bisembowel with. They have been known ton go into water when pursued by dogs and drown any dog foolish enough to follow, by holding it underwater with their front paws.