"... mice and dolphins, so this poll can be understood to ask about another species after those."

Actually, my initial thought, which prompted the reply, was about the group of species in the order Octopoda.

Something as different from us as a mollusc, does tend to go unnoticed, when considering intelligent creatures that share the planet with us.

While I wasn't really trying to provoke a philosophical discussion on the subject, it does beg the question whether we're intelligent enough to recognise another intelligent species.