We're just a little smarter and a little crueler. Most animals take what they need from their surroundings and if their surroundings are unable to support them, they adapt. We take as much as we possible can, because we can. If we use up the resources in a particular place, we expand and start draining other places. We have the ability to suppress other species and we do that in our quest for expansion.

We're just a little smarter and a little crueler.

@Jasper: You have a bit of a point, but we do know some of those things. We know that animals can think, but we have a higher aptitude for thought. This has been measured with things like cat scans, EEG's (electro-encephelograms), etc. Brains with a large and rapid amount of thought display more electrical activity. For example, dolphins have more cognitive aptitude than most animals...we know this from our scientific tests, and we confirmed it with field tests...the dolphins had a tremendous capability to learn and adapt. So we know that animals can have relatively intelligent thought, but we just have more of it. Doesn't make us any better in my opinion, but it's just a truth of the world that was understood by observation.