Here is a thought from Douglas Adams, the writer and dramatist who died in 2001. I was thinking of this watching the Grand Canyon Ravens last week. By exchanging “fly around” for “swim in the water” and “eat anything” for ” eat fish”, you get exactly the same thought about animal intelligence.
Humans think they are smarter than dolphins because we build cars and buildings and start wars etc., and all that dolphins do is swim in the water, eat fish and play around. Dolphins believe that they are smarter for exactly the same reasons.