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They may say they breed them, but, IMO, most likely they lie,
especially, if squirrels are legal pets (i.e., they know they won't be held legally accountable for having/selling 'pet' squirrels). If squirrels don't breed in captivity in the rest of the world, it shouldn't really be any different in China. Even if there is a chance of probability, a
very small chance (1 out of ...?...1000000) of getting a pair to breed in captivity (flukes can happen), it will be a very rare chance and definitely not sufficient to maintain successful business. To keep business going there must be a constant flow of goods (in this case, babies) and it's just very improbable.
Anyways, that aside, the rodent blocks suggested here on TSB are different from just any rat block. They are intended specifically for squirrels' nutritional needs. These blocks can either be purchased from www. henryspets.com, or made from sratch - there are recipes in our Nutrition section.
If some of the ingredients are unavailable in China, substitutes can be found. There are people from Eastern Europe who couldn't find all the ingredients and ended up finding substitutes... but I don't remember details here.
Please feel free to post
all your questions - people here will be happy to share their experience and knowledge.