Although several kinds of mammal exist on Lundy, only one, the pigmy shrew, is indigenous. This tiny beast has probably been there since Lundy separated from the mainland, about 8000 years ago. All the rest have been introduced, deliberately or otherwise, by mankind. The first of these was probably the ordinary house mouse, which has spread all over the world with human hosts. Rabbits were brought by the Normans in the 12th century, and have flourished. Less welcome were rats, both black and brown, probably from shipwrecks. Whereas in Britain generally, the common brown rat has almost completely ousted the ship (black) rat, on Lundy both species exist side by side. Three large mammal species live wild on Lundy; goats, which were undoubtedly brought by Stone Age settlers, and Soay sheep and sika deer, both recent introductions. The Soay sheep is an endangered species which originated on remote St Kilda, off western Scotland, and the sika deer came originally from Japan. It is to be hoped that Lundy can continue the be a refuge for these rare and interesting animals.