I will ask my husband what it was called. I know it is a black box b/c I see them set around on top of shelves and such in the coop. Our chickens are penned in half of the coop and the other half is storage and rabbits so he put the poison boxes by our storage. I think it would be a pretty slim chance that the dying mouse would then go into the penned portion to die but it just depends on how your coop is set up. I know mice are a constant issue with chicken feed around and a warm house for them to try to winter in. I will get back on here once I find out the name of the poison.What's the brand on the mouse poison? (And I still would probably have to be totally overrun to use poison since the chickens and other animals eat slow moving dying mice, unfortunately.....)