A wood mouse has been observed collecting unripe opium poppy seed pods and storing them in a drystone wall in a garden in Allendale, Northumberland. The mouse was seen severing stems of late-flowering poppies and manoeuvring pods, described as several times the size of its head, into a hidden store.
The plant, Papaver somniferum, is known as the breadseed poppy. While its blue-grey seeds are used in food, its unripe state is the source of opium, which contains opiate alkaloids including morphine, heroin, and codeine. These substances are found in the white, milky latex that oozes from damaged pods or broken stems.
A wildlife camera recorded the mouse returning multiple times to collect more pods. Research suggests that unripe poppies would spoil when cached, immature seeds have fewer nutrients, and even a small amount of latex could be toxic to mice.