There's probably already a thread about this somewhere, though I haven't seen it. However I haven't seen any articles about it, so I'm going to go ahead and post this.
In the first TLK film, the hyenas played a key role in the plot. They were essentially the bad guys, and it could almost be gathered that they were intended to be a species that was all bad. Some would even consider it was supposed to me a form of animal racism, though I'm not convinced it's quite like that. It was most likely supposed to give the Outsiders a rather Hitler-ish appearance, or at least an appearance of an evil regime. You'll notice that one of the most eerie scenes consists of a massive number of hyenas.


In TLK: SP, it was a completely different story. The hyenas were nowhere to be found anywhere in the film, it seems. This may be due to the fact that the creators of that film felt that the "racist" submessage of the first film wasn't something they wanted to have in the second film. After all, SP was largely based on "We are one" as a plot base.


Most likely, the hyenas were omitted due to the fact that they couldn't realistically, or very easily, be included in the "we are one" message. It could also be that they were generally stupid and had a gigantic population. Perhaps they didn't want to bring the hyenas back into the Pridelands in SP, as they had just been exiled in TLK1. Thoughts?