that's what happened to marius-- and this is where our story takes that dark turn. zoo six years ago, marius needed to move when he reached the age of two and did what adolescent male giraffes do-- start challenging their fathers, trying to take over the harem. >> holst: we could see that they had started fighting. and-- i mean, at the beginning, it's just a little bit pushing around. but then at-- at some stage, he started getting scratches on the side, because the father had pushed him up against a tree and had really hit him hard. and if we have left him with the father, he would have killed him, i'm sure. >> stahl: in the wild, this is when marius would strike out on his own, a time when in nature, many animals are killed by predators. but in the zoo, there was nowhere for him to go, and with no spots for him in the european breeding program, the zoo thought their only choice might vebe so uggestions t of what to do, short of killing this beautiful animal. some people said, "why not just release him in the wild?" >> holst: yeah, we cannot just release a giraffe