Hey !
Well done ! It was a pretty funny game.
I liked the theme and the gameplay. The upgrade system is not perfect but it's there and it's not tedious.There is some Z index that aren't perfect but it's not afecting the fun of the game whatsoever.
Overall a great game!
Try to make some kind of setting window, it's easy to take from game to game and score easy points.
The music is catchy but quite repetitive.
Try to notify the player when the encyclopedia is full, I search for the last animal for minutes before seeing the encyclopedia and learning that I was finished ^^ (après je suis peut être con aussi :D)
Keep at It !