Baby fish babbling
"Babbling" is the first stage of language development in humans in which infants make sounds that are considered pre-linguistic and practice for future chatting. Babbling has been found in several other animal species (including bats, monkeys and parrots), and now maybe in fish? Turns out that baby snapper (larvae) make "knocking" sounds that adults also use, which function to keep fish together in their schools. Read more here.