This is an open bug that was archived. I am not sure if a new bug report is meant to be made.
Animal aging is turned off in options. Aging is turned off for all sims.
I have a save file I have p...
Ideas
I just had this happen today, I switched to my household with cottage living animals and Grim collected ALL of them, including two brand new chicks. Animal aging is off, and I play on console, so I have no mods.