buying your mice
What to consider when you are going to buy mice? Well, several things! How many do you want? Males er females? From a breeder or a petshop? How do you know they are healthy? Do you want to breed with them or are they just pets?
The first thing would be how many you want, I allready noted you should at least buy 2, but I advice 3 as they are sensitive and it is always possible that one dies. But if you want to breed, three is maybe not enough? You can buy a male with 2 females, but what male will you use for the next generation? If you want to breed without any inbreeding, you will need about 3 males, at least! And I advice about 2-3 females per male. So Let's say you will have at least 10 animals when you want to breed.
Now, if you want to breed, healthy lines are in my eyes even more important then when you want to keep them as pets, but no one wants to buy a mouse with health problems on purpose as they could die early or will cost a lot of money "fixing" them, so best is to reduce the chance on deceases. A breeder also can't promise a mouse doesn't get ill, it's a living creature and they also can get a virus or someting. But "breeders" that don't keep an eye on health will have more baby's per litter, more litters per mother, so less milk and a in most cases, weaker mother as she didn't get the chance to get back in shape before her next litter and that will often mean that they have less of a immune system. And also genetic problems will develop more often as they most times don't keep track of what parrents and lines gave the ill baby's or what baby's are from that male that has tumors etc, so they can't select on genetical issues.
A petshop is always a hard choise, I honestly say I have bought mice from petshops, but with most cases I can now say it wasn't the smartest thing to do. Petshops often buy their mice (and other animals) from one suplier, who often sell their animals to more then just one petshop what means they have a lot of animals and are most likely one of the "breeders" that don't keep an eye on health, but just want to produce as much mice as possible. And because they have so many animals and often use cheap products and food for their animals they can sell their animals for less then a good breeder can wich is much cheaper for the petstore so they can make more profit.
But still, this isn't something all petstores do, some really want "better" mice, and ask better breeders, but often they ask more then the breeders asks, so they won't sell and the petshop stopt selling mouse as they can't get rid of them.
When buying mice, my advice is to go to a good breeder, watch how the mice are kept, is everything "clean", do the animals seem healthy? And then look at the available mice, a mouse will only seem ill when it really is. When they look sick, they are and will most likely die when you bring them home because of extra stress. So make sure their furr is nice and clean and not standing up or anything, their eyes, nose, mouth and ears clean and their butt too! Another thing to watch is their size, when they seem way too young, they often are! Size isn't always the way to see wich are younger, but when they are young they usually are a bit jumpy and thin, when they pass 4-5 weeks, they get a bit more fat on the bones and seem more like a adult mouse.