When ferrets are first born they are known as kits. They only weigh 8 to 10 grams when they are born and can easily fit into a teaspoon. It takes only 10 days for them to grow 3 times bigger then when they are first born, from only their mother ferret's milk. Baby ferrets spend the first three weeks of their life sleeping and nursing. The kits develop teeth after only two weeks, but it takes a full month for them to open their eyes and to begin hearing.When the baby ferrets are three weeks old, they are 10 times larger then when they are born. At three weeks they are able to eat solid food, but will still mostly nurse from their mother. It is around this time that the kits will start to produce a sound that resembles a goose honking to attract attention, but lose this ability when they are around two months old.A baby ferret's skin is pinkish when they are first born and have a very foul odor. This is likely part of the baby ferret's natural way of fending off predators. After a few days after birth they begin to grow fur, and almost after a week of life the fur begins to turn color. When the baby ferret is around 3 weeks old, it will become apparent what color the ferret will be when it grows older.The difference between male and female kits becomes obvious around 6 weeks. Male kits will be around a full 50% larger then their female counterparts. Female kits reach full size after 4 months and weigh around 600 to 800 grams, while males reach full size around 10 weeks.