I haven't researched fish thoroughly yet, but at least whales definitely talk :).
I'm glad to hear that someone besides me sees the learning potential in this game!
I agree about more gamification, as an option I was also thinking about mini-games after each question, for example, if you guessed that it sounds like a cheetah, then you have the opportunity to play a mini-game with a cheetah, or move on to the next question. The mini-game itself will also reveal some characteristics of the animal, if it is a cheetah, then it is the fastest cat, so the mini-game will be related to speed, for example: run away from it; catch it; hunt for prey, etc. Or just a simulator of an animal in its environment :). Or whatever comes to mind ;).