It's hard to call it a fight, but here you can clearly see how kangaroos use their tails, which can

It's hard to call it a fight, but here you can clearly see how kangaroos use their tails, which can be called a fifth limb without hesitation. Without a tail, kangaroos would not be able to move, stand up straight, or fight. This is very important when the kangaroo is moving at high speed; when its tail swings in sync with its legs, helping it, creating additional momentum forward and preventing the kangaroo from falling backwards. As you can clearly see in this video, kangaroos can only hold their entire body weight on one tail, which allows them to stretch their legs towards the threat.