Books in Young Reader's Series series

A visitor to the zoo climbs on board the double-decker tour bus expecting to get a clear view of all the animals. But he soon discovers that not all the zoo inhabitants are easily found. As he approaches each exhibit, he strains to spot the occupant without success (although a sharp-eyed reader is likely to spot some clues to the whereabouts of each elusive animal). Shouting out, "Where are you?" brings back the response, "Look again. We are here." And sure enough with a second glance, he finds the missing animals. This classic peek-a-boo, where-are-you story offers a slight twist, however, when the bus reaches an overlook from which the visitor can see no animals at all. "Now where did you all go?" he calls out in exasperation until he once again takes a second look and discovers that all the animals have joined him on the bus.