1For kangaroos, the greatest challenges come from within their own society.
2For a male, there's only really one key lesson to learn in his life.
3To get to the top, he must become a fighter.
4The battles are so brutal that males need years of training to prepare.
5The effort is worth it, because a champion fighter wins privileged access to the females.
6This meadow is a boot camp for aspiring boxers.
7Training starts as soon as a youngster is out of the pouch.
8Its mother is a handy opponent for a young joey learning the basics.
9...
10But he's soon off in search of more sparring partners.
11...
12The other grown-ups are not so tolerant of this lightweight.
13...
14This male alone rules the meadow.
15He stands eight feet tall, his muscles hardened by years of sparring.
16Today, a challenger for his title has come forward.
17Full-blown fights are so dangerous, they're not entered into lightly.
18But when two males square up, it's time to clear the arena.
19...
20Anything goes in these power struggles.
21Eye gouging is entirely within the rules.
22...
23So is kicking below the belt.
24The dominant male's skill is already telling.
25...
26The stakes are high.
27They risk broken bones and internal injuries.
28...
29Suddenly... it's all over.
30The champion has beaten off the challenger, at least for now.