Mice that have been exposed to radiation. These mice usually live in nuclear plants and may have become radiation resistant. However, they pose significant risks to humans if some of them migrate to places outside of the nuclear plants.

Radioactive mouse droppings have recently been discovered in the grounds of the Hanford nuclear plant in Washington State, USA. It came two weeks after a radioactive rabbit was captured on the same site. The mouse and rabbit droppings were found in the same area, indicating that the animals ate or drank a common source of radioactive contamination.