Cages aren't signs, okay? Certain idiots straight up ignore the cage, speaking from experience and Strange's slightly bleeding finger. He puts said finger up to his mouth for a moment as if licking the wound will help close it.

"However, I doubt that book's the most dangerous animal we have here. What's the most impressive creature in this menagerie?"

It's straight up an opportunity for Ginko to show off some dangerous looking critter and Strange knows it. Come on, Ginko! Show him something cool!