The winter white dwarf hamster (Phodopus sungorus), also known as the Russian dwarf hamster, Djungarian hamster, striped dwarf hamster, Siberian hamster, or Siberian dwarf hamster, is one of three species of hamster in the genus Phodopus. It is ball-shaped and typically half the size of the Syrian hamster, so is called a dwarf hamster along with all Phodopus species. Features of the winter white hamster include a typically thick, dark grey dorsal stripe and furry feet. As winter approaches and the days shorten, the winter white dwarf hamster's dark fur is almost entirely replaced with white fur. In captivity, this does not usually happen as animals maintained as pets are generally housed indoors and exposed to artificial light that prevents the recognition of short winter daylengths. In the wild, they originate from the wheat fields of Kazakhstan, the meadows of Mongolia and Siberia, and the birch stands of Manchuria. Winter white dwarf hamsters are common as pets in Europe and North America, and exhibit greater variance in their coats than those found in the wild. They reproduce often—more so than Syrian hamsters, and as they have no fixed breeding season, can continue to produce some numbers of offspring all year round. Young pups act aggressively to one another, while breeding females may show similar aggression to males. The winter white is known to be one of the most tameable types of hamsters. Naming The hamster has no fully accepted common name, winter white dwarf hamster and Russian dwarf hamster are among the most often used. Confusion arises because of their physical similarity to Campbell's dwarf hamster, consequently, the name Djungarian hamster and Russian dwarf can refer to both winter white and Campbell's dwarf hamsters. The term "winter white" derives from the fact that in the wild the hamster changes its fur colour to white for the winter months, this camouflages the hamster and reduces predation when snow is on the ground. Campbell's dwarf hamsters do not change fur colour during the winter and can only be described as being "winter white" erroneously. The binomial name for the hamster is Phodopus sungorus. The hamster was first described by Peter Simon Pallas in 1773 as a mouse. The name sungorus derives from the geographic region Dzungaria. In 1778, Pallas renamed the hamster to Mouse songarus. In 1912 Ned Hollister ordered the "Mouse songarus" to the genus Phodopus. A. I. Argiropulo, in 1933,