Are you 100% sure it was CB? I find it hard to believe a chain store is selling CB balls when CH are so much cheaper. I know Petco on the westcoast gets their balls from a vendor, who gets them from another vendor who imports CH babies. I would be surprised if Petsmart didn't have a similar system in place.
In any case, try a live, adult mouse. Anything smaller than a crawler isn't worth much to a ball python - even a hatchling. Baby mice are just too small. Chances of the snake getting mites from the *mouse* are slim to none - mouse mites and snake mites are two very different beasties. Mammalian mites aren't gonna latch onto a reptile. There's a greater chance that the snake gets mites from the ones that are usually crawling around the store.
Back to the mouse. Keep an eye on the two to make sure that the mouse doesn't hurt the snake, but if the snake is hungry it'll eat the mouse. Only offer a mouse once a week - more often tends to be stressful. If the snake doesn't eat it after 15-20 minutes, take the mouse out and wait til next week.
If it doesn't eat, don't touch it. Don't take it out to show your friends, don't handle it, don't try and tame it, nothin. This is the hardest part! The snake has to get the chance to settle in, realize it's in a safe place, and stop stressing. You'll know the snake has settled in and feels secure when it starts to eat regularly for you. This means it eats at least twice in a row, preferably 3 or 4 times.
Good luck! Enjoy your snake!
~jenny
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"The python has, and I fib no fibs,
318 pairs of ribs.
In stating this I place reliance
On a seance with one who died for science
This figure is sworn to and attested,
He counted them while being digested."
~Ogden Nash
jenny.thegreenes.org
"If you're happy and you know it,
Bomb Iraq!
If you cannot find Osama,
Bomb Iraq!
If the terrorists are frisky,
Pakistan is looking shifty,
North Korea is too risky,
Bomb Iraq!
