Rats will attack anything defenseless.
actually,rats will not attack unless they feel they are in danger,they are not horrible monsters. the article states that it was suspected that milk had dripped onto the baby's lips and that is what spurred the rat on. the rat wasn't attacking,it was trying to get the milk off the baby and probably got a little too overzealous and started chewing. It happens easily,with Domestic as well as wild rats. I would know,i've been bitten many times on the nose and lips by my rats from where they're jsut trying to get a little cheese or milk off.