be honest was it your first instinct to check if they are?

From what I remember, on my first play-through the first thing I tried to do was explore, and when I got near the critters I was attacked. I don't think I even knew how to use my gun, so I just ran away.

In the real world, non-evil animals are often territorial. OTOH, they're often also curious, and if you approach slowly you can end up interacting with them without it coming to violence. But, the biters in Factorio go straight from ignoring you to attacking you with no in-between.

As for colonizing, it's worth noting that the goal in Factorio isn't to establish a colony, but to escape after your ship crashed.

I do like that the game subtly makes it clear that you're causing a lot of pollution, and that basically the only reason the natives attack is because of your pollution. OTOH, it would have been better if the biter "nests" contained something like worker ants who didn't attack you but needed to be killed to wipe out the nest. I guess you could argue that the spawner things fill that role, but they don't seem to do anything other than pump out enemies who immediately attack. So, not really.