Although I do not necessarily disagree with feeding them strictly rats, and I have heard before about what you are describing, I have never experienced a pit not wanting to eat rats. I have raised pits on both mice and rats, more on mice due to food size issues, until the snakes get full adult size, and actually have had just a few take mice for years, then seem to only want rats and then the occassional mouse. Never though have I had some only want rats, but I do know it can happen. A good friend of mine who breeds pits never has had that happen either, but like I said, I do know it can. Shows that they can be stubborn!! LOL!
I know one guy whose adult graybanded king didn't want anything but small fuzzies....so he has to feed him a big pile of them! LOL!
Heck, my biggest pits got to be enormous from retired breeder mice. At this time, my biggest pits though do get both or either rats and retired breeder mice.
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Genesis 1:1