Take Kangaroo for example.Kangaroo, once or twice each year reproductive kangaroo in about 30-40 days of ivf is born, very small, no vision, less hair, immediately after birth mother kangaroo in the conservation of the bag. Until 6-7 months began a short time study life. Conservation bag A year later, can leave conservation bag was formally, still mother kangaroo in nearby, always get help and protection. Mother kangaroo can also have a bag of kangaroo, in a bag of wallabies and a room of the kangaroo.