I am puzzled why Chomper left his parents. That was never explained to my satisfaction in the series.
The best explanation we got was that Ruby was keeping him ''safe'' for them. For whatever reason, that was never revealed. Which is quite dumb, if you ask me. Perchance it had something to do with Red Claw, but that was never confirmed.
I remember there was one episode (don't know which one) where they showed a flashback of Ruby saying goodbye to her parents, and they were saying she and Chomper needed to go to the Great Valley to find out how the dinosaurs there coexisted and worked together or something like that, since that knowledge could help defeat Red Claw one day. Still not a satisfying explanation for me, though. Why are Chomper and Ruby the "chosen ones" to make this discovery? Why do they make it sound like Chomper and Ruby are on some sort of mission when all through the rest of the series, it seems like they're not actively making observations and seeking knowledge about teamwork and whatnot so much as they're just hanging around and having fun with the other kids?