That's the title of a limited edition portfolio by Swiss animal artist Fritz Hug.
The publishing date is unknown.
Hug visited the zoo in Zurich so many times that he knew a lot of the animals by name.
I enjoy his loose quick sketches, but also the drawings that took a little longer, when he took the time to define textures like fur, feathers and skin. But most impressive is his observation and his knowledge of what pose brings out the animal's characteristics.
If you missed my first post on Hug's work, here is the link: