Editing Winter white dwarf hamster (section)

==Breeding==
Winter white dwarf hamsters reproduce at a faster rate than Syrian hamsters.<ref>{{cite web|url=http://www.ask-the-vet.com/breeding-hamsters-breed-hamsters.htm|title=Breeding hamsters - how to breed hamsters|access-date=8 August 2011|archive-date=12 December 2013|archive-url=https://web.archive.org/web/20131212043437/http://www.ask-the-vet.com/breeding-hamsters-breed-hamsters.htm|url-status=dead}}</ref> Research suggests biparental care in Campbell's hamsters (''P. campbelli'') but not in winter white hamsters (''P. sungorus'').<ref>Research by Dr. Katherine Wynne-Edwards at Queen's University, Ontario, Canada</ref>  Frequent fighting can occur between the pups and as soon as they are weaned from their mother, they are separated from her.  Most of the dwarf hamsters grow to 3 to 4" long. Hamsters maintained indoors that get artificial illumination during autumn and winter are likely to breed all year round, whereas in the wild and in animals maintained in captivity but under entirely natural light-dark cycles, breeding is restricted to the long days of spring and summer.<ref name="How2care" />

During the breeding time, the hamster may become aggressive. After mating, the female may want to attack the male to protect her babies. The male usually hides in holes or caves to escape the vicious bite of the female.<ref>Sandra Honey: ''Dwarf hamsters. Biology. Attitude. Breeding''. 2nd Edition. Nature and animal-Verlag, Münster 2005, {{ISBN|3-931587-96-7}}</ref> The hamster's [[estrous]] cycle lasts four days; every four days, the female may accept the male back to breed again. This usually occurs when the darkness of the evening sets in. If male and female hamsters are not housed together from a young age, determining if the female is willing to breed with the male is difficult.<ref name="aboutpets book" />

===Hybrids===
Of the five species of hamsters kept commonly as pets, only Campbell's dwarf hamster and the winter white dwarf hamster are able to interbreed and produce live hybrid offspring. Although hybrids make suitable pets, the breeding of hybrids and [[cloning]] can cause health and reproduction problems. In addition, the widespread breeding and distribution of hybrids could threaten the existence of both pure species and subspecies of the ecosystem, resulting in only mongrels. Hybridizing causes each litter to become smaller and the young begin to form [[congenital]] problems.<ref name="aboutpets book" />