I enclosed 12 wild puft (different variations) in a large area, not overcrowded, with a chlorine geyser which in the end filled almost whole area. From what I understand no wild critter will die before laying one egg and they don't die from starvation. Yet whole population went to extinction.
I think the chlorine environment and so the lack of food lead to lowering reproduction rate for wild pufts, but I can't confirm that as wild animals have "reproduction" stat removed, you can only see it if they are tamed, which is logical as long as it's assumed wild animals always should lay one egg before dieing.
The temperature of the area was great thanks to the geyser, not overcrowded, and even I was expecting them to convert to squeky pufts over several cycles of laying eggs. You can see already two of them (was none in the begining) on the first screenshot. I don't have any container set to storing eggs, neither egg cracker is set to destroy them. You can see plenty of egg shells on the ground (probably from the times where there still was polluted oxygen in the room, or times when they are turned to prince puft). (Also why they age is so synchronized? How this happens?)
Why the whole population died then? Also without any warning that they won't lay egg - if the reproduction rate is supposed to lower when in hunger then it should be visible.
Sincerly really sad over spiecies extinction - wanted to have wild env where all pufts could live happy lives - ended up with extermination.
Steps to Reproduce
Close pufts in chlorine and watch over bazillion of cycles if they will lay egg.
This issue has not been confirmed by a developer yet.