I know both authors, so I wrote them to ask. This is a rogue image that appears in various PDFs posted online, but not on Springer's official PDF or any print copy we've seen.
Pretty sure that's a ferret.
oh yeah! that is insane.
I think it's cute!
What if it's steganography or symbolic or a puzzle.
If it's none of that, to complain about it is a bit too harsh.. for something on page 67.