I think rats and hamsters fall under Pocket Pets. Not all exotic vets have the designation as it seems to be fairly new (you'll notice all of the vets at Lupu don't but they are all able and experienced to treat them) but those on the list have the education/experience to treat exotic mammals. I will usually look more closely at a vet if they can treat rabbits, guinea pigs, and ferrets... even if they don't have a lot of experience with rats but are willing to learn and there are a lot of similarities with the other 3 species.