Mice are very good at hoarding food and will often take any food they find back to their nest. This means that if you put out poison bait, there's a good chance that the mice will take it back to their nest and share it with the other mice. If you want to ensure the poison kills all the mice in the nest, you can try using a tracking powder. This powder will stick to the mice as they move through it and help you track them back to their nest.