The Northern White-breasted Hedgehog (Erinaceus roumanicus) is a small mammal, easily recognised by their many spines. They are secretive nocturnal animals which, when threatened, roll themselves into a protective spiny ball. These hedgehogs have a pale chest and belly and their spines are hollow hairs made stiff with keratin. The size of Northern White-breasted Hedgehogs varies depending on temperature and they are typically larger in warmer areas such as Greece.