For about the first month or so that I had my beep, I was accidentally feeding him prey that was too small. In anticipation of his arrival, I went to PetSmart and bought a package of small mice, since that seemed about what the breeder said he was being fed. As it turns out, ArcticMice run small for their size, and beep was already too big for them when he came home. I've since found a different pet store to buy my feeders from, and keep a chart in Excel to track how big he is and how big his food should be by weight.