They do vary. Where I am, Petsmart is one of the better ones. There's still the dreaded Oxbow, but the hamsters aren't overcrowded (the tanks aren't big, but it is temporary). I've never seen any noticeably sick, injured, fighting, or dead rodents. They need to update their care recommendations and product selection, but the rodent section isn't a scene from Lord of the Flies. And I always look at the rodents. I can't vouch for the fish or other departments because I don't usually check them out.
There are basic laws governing large animal mills (these include regular inspections), and major pet shop companies want animals from clean facilities. It doesn't do them any good if the "product" dies in the store, or if a child develops an infection after being bit by a recently purchased hamster (that's not going to go down well for the store, regardless of how many disclaimers they make you sign). Obviously, we'd like to see improved regulation, and some mills slip "under the net" for a time; but severe cruelty is not profitable. They need to deliver "bright-eyed and bushy-tailed" animals, so that the large pet shop companies keep a contract with them.


























