洋書・Simon and Schuster Childrens Books・Susan Schade and Jon Buller 「The Fog Mound / Travels of Thelonious」です。
「In a world of talking animals, there is one burning question: did humans ever exist? Thelonious Chipmunk believes he has proof that they did: a postcard showing a building made of concrete and glass. But his sister thinks the postcard is just a silly piece of paper - everyone knows humans are only make-believe! When, one day, a flash flood carries Thelonious away, he wakes up in a strange world that looks something like his postcard, but not quite - it's crumbling and decaying. If this is proof that humans once existed, where did they go? Thelonious sets off to find out, and the adventure begins!」(Amazonから)