I would change the substrate from newspaper to a nice thick layer of aspen. Corns, milks, etc. love to burrow and it makes them feel more secure and safe to be able to do so. The tail rattling is a defensive mechanism. I'd add in a couple of very small hides plus some fake vines, etc. Basically anything that gives the baby milk something to slither around, through and under for cover. Remember like all colubrids, this one will be an escape artist so a good lid with tight clips is a must. Sounds like you are off to find a pinky mice supplier LOL.