Ireland's terrestrial mammals has been heavily influenced by humans, both through introductions and extinctions. There are 26 species of terrestrial mammals. Some may have survived the last Ice Age - the stoat and mountain hare, others such as the bats, seals and the otter may have migrated here naturally. Other species, such as many of our deer, have been deliberately introduced and others species will have arrived accidentally, such as mice and rats. Species such as the Irish elk (Megaloceros giganteus) are long extinct.