They are cinnamon brown in color with white under parts that have a yellow tinge. Twice a year these weasels shed there fur, once in the spring and again in the fall. The shedding of weasels is controlled by photoperiod. The main prey for the long-tailed weasel is small rodents. Females, with smaller bodies, have better luck getting the small rodents because their bodies can fit inside the small rodent burrows.
Males pursue larger animals, for example the eastern cottontail.
After copulation, implantation is delayed and the egg does not begin to develop until March, making the total gestation time around 280 days. Birth occurs from late April to early May, and the average size of the litter is six. At birth, the young weasels weigh about 3 grams. They are pink with wrinkled skin, and they have white fur. At fourteen days, the white hair begins to thicken, and size differentiation makes it easy to tell males from females.