Why? -SPOILERS-
Why does this sabertooth kill so much? I mean, at first with the janitor I thought, "Ok, it's hungry and the guy is an idiot for not waiting to make sure the gate closed." But once we get to the second death, it seems like the animal goes out of it's way to kill the guy transporting it. It just gets out of it's crate and immediately decides to hunt this guy down, even to the extent of tearing open the roof of the truck. Surely if it was hungry it would have realized he wasn't worth the effort and moved on to look for easier prey?
Which brings me to the next death(s), the man and woman who've just finished having sex and are getting ready for another round. You're in the middle of the woods, at night, yet you get the uncontrollable urge to wander off to find your cat. I understand the sabertooth killing the woman (though she's seen clinging to life later, it's pretty obvious she dies), even though it just ate not too long ago, but WHY go after the guy? You've got this woman here, easy enough food, but no, it's a good idea to go after the guy (who you can't even see) and use up unneeded energy breaking through the door to grab the guy (with unrealistic accuracy).
I won't go on to list all the other deaths, but to sum up what I'm getting at:
It seems like the animal is killing just for the sake of killing. It will kill (and presumably eat at least some of) one person, then immediately start hunting down another. I don't know of any animal in today's world that will kill for any other reason than to feed or defend itself. Clearly the sabertooth isn't threatened by any of these people, so that rules that out. And, even though it's a big cat, I highly doubt it needs to feed every five minutes.
But I could be all wrong, no one knows exactly how this animal lived back when it was a top predator, they can only speculate. But that's it for my rant, and it's probably the longest post I've done on any forum. Shame I wasted it on such a bad movie.
I'll never turn to the Dark Side. I am a Jedi, like my father before me.