Nice game! I ended up playing for a while. Im on level 6 right now. I don't know if it was intentional but I could cheat the timer by holding the bunnies until I met the condition
We hint the player about this possibility at level 4, so it is planned. (in the settings window at level 4).
But it is not always safe and controlled to hold rabbits in your hand, sometimes they manage to breed before you grab them again or they can even infect each other in your hand!