The coat of the winter white dwarf hamster ( Phodopus sungorus) turns almost white during winter (when the hours of daylight decrease).

Molecular phylogeny of the Cricetinae subfamily based on the mitochondrial cytochrome b and 12S rRNA genes and the nuclear vWF gene" (PDF). Gestation lasts 16 to 18 days for Syrian hamsters, 18 to 21 days for Russian hamsters, 21 to 23 days for Chinese hamsters and 23 to 30 for Roborovski hamsters.

in) long; the largest is the European hamster ( Cricetus cricetus), measuring up to 34 cm (13 in) long, not including a short tail of up to 6 cm (2. Effect of Exercise on Photoperiod-Regulated Hypothalamic Gene Expression and Peripheral Hormones in the Seasonal Dwarf Hamster Phodopus sungorus". The name "hamster" is a loanword from the German, which itself derives from earlier Middle High German hamastra. The hamster tail can be difficult to see, as it is usually not very long (about 1⁄ 6 the length of the body), with the exception of the Chinese hamster, which has a tail the same length as the body. Both Syrian and Russian hamsters mature quickly and can begin reproducing at a young age (4–5 weeks), whereas Chinese hamsters will usually begin reproducing at two to three months of age, and Roborovskis at three to four months of age.

If housed together, acute and chronic stress might occur, [8] and they might fight fiercely, sometimes fatally. The average litter size for Syrian hamsters is about seven pups, but can be as great as 24, which is the maximum number of pups that can be contained in the uterus. The Roborovski hamster ( Phodopus roborovskii) is extremely small and fast, making it difficult to keep as a pet. One rodent characteristic that can be highly visible in hamsters is their sharp incisors; they have an upper pair and lower pair which grow continuously throughout life, so must be regularly worn down.

Fritzsche indicated although some species have been observed to show more nocturnal activity than others, they are all primarily crepuscular.