That is when I learned that compassion for rodents is basically suicidal insanity, and stopped trying to co-exist with cute furry little superspreading plague bearers.

I'm glad you enjoy the privilege of having had others kill them for you, but someone most assuredly did, and the reason you haven't died of the plague already has a name: specicide.

An average number of rodents in a wilderness environment is 200 per acre and approximately 10% carry hantavirus.

They also carry the plague, typhus, lymphocytic choriomeningitis, and several other presumably horrible diseases that I've never even heard of.

This is, in fact, the reason the habitat under discussion is a sealed box with a "lifetime" supply of food, water and filtered air exchange.