There are two species of hamsters kept as pets that are capable of interbreeding; the Campbells and the Winter White. These hamsters live in completely different areas; therefore the possibility of hybridization occurring in the wild is unlikely. When interbreeding occurs, the female must always be a Campbells because they have a wider head than Winter Whites. The offspring of these animals are often larger than the standards for either the Campbells or the Winter White.
The mixed breeding of the Campbells and the Winter White dwarf hamster is occurring out of ignorance and greed. Many commercial breeders believe that cross-breeding will allow new color mutations for the Campbells and Winter Whites, giving them an opportunity to advertise a “rare” hamster for more money. Hybrid hamsters will only produce hybrids. Breeding for new colors between the two is only delaying the process naturally since it’s harder to find pure stock, depending on where you live.
Colors aren’t the only thing being passed down; diseases commonly found in one of the species are showing up in the hybrids. Glaucoma from the Winter White lines and diabetes from the Campbells are among the most popular diseases between the two. A strict diet must be enforced to reduce the chance of diabetes.
If interbreeding became popular enough, it would eventually make it nearly impossible to find Winter White or Campbells aside from the few breeders who keep track of their lines. Hybrids have a high chance of producing infertile offspring, so it would prove difficult to support an indefinite line of hybrids.
I personally believe that no hamster fancier would intentionally breed hybrids.