You can see a huge difference in just 11 days. When ferrets are born their eyes and ears are still closed and they do not open for at least 3 weeks after birth. The mommy will put her scent on the babies in case she has to go out and get food she can find her kids if they get out of their hidey hole.

Since their eyes and ears are not open at this age they do not travel far. The mommy does not let her kids out of the sleep sack or hidey hole. If they can not find mommy they will cry out with a very high pitch chirp almost like a bird.
Click here to see pictures of kits 1 month old.