I think it'd be more realistic if the two different types of predators ate each other when the herbivores start to run out. It'd also balance the game out nicely, as it is predators overwhelm the herbivores a little too fast.
I think that the game is really difficult as you get nearer the end ( As it should be ) but my main problem was that the keys kinda stop following the rhythm of the music. But then i found out that if you played on the Pro level that it gets not only harder, but matches the music exactly. 5/5, Its a great game as are most of yours. I've been playing SCGMD3 until i got a perfect on each one, then it was just a matter of waiting for your next masterpiece.
A very good game. When you start playing it, you don't suspect the ending, but when you do get to it, it gets you thinking. While not personally familiar with the psyche of self-mutilation, i have seen the effects on a lot of my friends, and I've noticed that all of them take one of these three routes. Kudos on a good game, and a good philosophy.