There is little courtship behavior in hamsters. Since hamsters do not enjoy living with others, the male is placed in the female's cage when she is receptive. As estrus approaches, the female hamster develops a clear, stringy vaginal discharge, accompanied by a characteristic vaginal odor. This odor is thought to attract males, as well as to stimulate males to male fighting, and to keep other females away. At this time, one hour before dark, the male can be placed in the female's cage. After copulation, or if fighting begins, the male is removed.
To learn more, read Courtship in Small Mammals.