How Fievel survived by walking the streets.

After the middle child of the Mousekewitz family is seprated, he seems to have a very good survival skills. I need to know how long or how did he survived. I don't know he survived 4 and the half days or not, because his family found him in a Orphan Valley (unknown to survived 4 1/2 days). I hope anyone guess this right. I've enjoyed researching An American Tail's characters, places, cast&crew and real items.