Hi Dave,
thank you! Yeah when I first got him he looked small (short) for a year old. I was never sure if he really was a year old. I never noticed his backbone and no one else ever did. Everything else with him has been great-he had a perfect shed so yay! He doesn't look underweight so it's really puzzling. Either he is underweight or he's not really a year old and the guy I got him from doesn't know anything... I'm going to go ahead and feed him another rat fuzzy today and next week, I'll move him up a size in rats. I'll definitely be monitoring Leo's weight much more closely.
Thanks again!