Of Mice & Men: Habitats Supplement Natural Violence

In captivity, male mice bred as pets are taken as soon as they're weened and often placed in glass habitats in pet stores in large groups. They live in adorable harmony for a few weeks: sharing food, grooming each other, and sleeping in a cuddle pile. Then they reach sexual maturity and everything changes. If not separated, the mice will fight and kill each other, until the one dominate mouse survives. Why is this? The mouse never had contact with his father, so he did not learn this behavior from him. Is it simply nature? Not quite. There are a few factors contributing here. First, the mice are in a habitat that is too small for the number of mice, but economical for the store. There are not enough "homes" for each mouse, and they are literally living on top of each other, in their minds forced to compete for their survival. If they are sold quickly, and go home to adequately sized cages, then the mice are never known as killers, but sweetly tamed pets. In nature, there's ample room for them to spread out and establish their own territories without ever killing each other.
Now, are humans like mice? Not quite. But sort of. I believe both have some sort of predisposition to violence naturally. It varies from mouse to mouse and person to person. Also, what it takes to draw that violence out of an individual will be different. For a mouse it may be as simple as the other mouse eating out of his food dish, while another mouse might only act in violence to physically defend himself. For a human, maybe he sees that the other human has something he needs to survive or maybe he sees that another human has something he wants.
I think, just like the mice kept in the pet store habitat, the society and culture we live in now helps to foster the violence. At all ages we're bombarded with imagery of violence and hate. War and action heroes slaughter numerous faceless victims without negative consequence. And of course the ever-cited video games: gratuitous violence, demeaning images of women, etc. In an atmosphere like this I think it can sometimes intensify what may be naturally there. It certainly isn't helping counteract anything.