Kids books can seem bizarre and many times quite sexist when looked at from an adult's point of view.
  1. The zookeeper is very bad at his job
  2. The zookeeper comes home and wakes his sleeping wife, who has to clean up his mess
  3. The wife manages to return most (if not all) of the animals and return to bed without waking the already sleeping zookeeper.
  4. The animals are very well behaved.