In the second winter, only a few change into the winter coat and winter colour is less pronounced. The moulting in the winter fur starts in October or November and is completed in December, while the summer coat begins in January or February and is completed in March or early April. The ears are grey with a pinkish tint. Moulting both run jobs on the head and the back of the spine to the sides, the legs and the underside. The hairs grow longer in the summer, to about ten millimetres long. The pigmentation of hair is controlled by the hormone prolactin and colour genetics. Day length can be less than 14 hours to initiate the change to winter coat, though it is possible they may be able to sense a directional change in photoperiod length, such as in one experiment that demonstrated a transition from 16 hours of light to 14 hours initiates a change to the winter coat. The change to the winter coat can be triggered in the summer by the short day lengths. The change occurs back to the summer coat in the autumn, when the length of the days change again. At internal temperatures hamsters in captivity start later with the changes. The winter colour is less pronounced in them. The eyes of the winter white hamster are black, unless it is albino in which case they are red. In the wild In the wild, the hamster's fur changes colour in the winter. This adaptation helps them to evade predators in the snow-covered steppes. The hamster digs tunnels one metre deep leading to ground burrows where they can sleep, raise their young and hide from predators. The weasel is one of the hamster's main predators. Most of these burrows have six entrances. In the summer, the burrows are lined with moss. To keep the burrow warm in the winter, the hamster closes all but one entrance and lines the burrows with animal fur or wool that it finds. The temperature inside the burrow is usually . The hamsters sometimes live in the semideserts in Central Asia. They also live in the dry steppes and wheat or alfalfa fields, as well as on small fields in the forests of the region around Minusinsk. The fur on the hamster's feet protect the feet from the cold ground in the cold climates in the wild. The population density