First off, for sure don't start worrying. They will be fine for quite a few weeks. Once you hit 6-8 weeks I would start to worry some if you have been trying all along with no success, but until then I wouldn't worry too much.
Secondly, I have found that getting them to take PK or FT right off the bat can be pretty difficult, but as a second or third time eating they will frequently take either. That first meal not many of them seem to be able to identify the nonmoving rodent as a meal, but after they have eaten a few times they seem to catch on and do fine.
Also, starting right away with rats also seems to be a little slow, even if they are live...but it sure is nice if you can do it this way so that you don't have to switch them later. So, I usually try live rats 2 or 3 times and any that don't take them, then I leave a live fuzzy in with them overnight and I would say by this point I usually have 80%-90% eating for me. The few that still don't eat, I usually start taping them on the body (usually mid body and tail region) with a mouse fuzzy to get them to strike, and quite often once they strike a few times they will eventually go ahead and constrict and then eat. After they have done this a couple of times they usually catch on.
Anyway, there is some brief info, let us know if you have any other questions.
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Ben
www.australianaddiction.com