A hedgehog is any of the spiny mammals of the subfamily Erinaceinae, which is in order Erinaceomorpha. There are seventeen species of hedgehog in five genera, found through parts of Europe, Asia, Africa and New Zealand (by introduction). There are no hedgehogs native to Australia, and no living species native to the Americas. Hedgehogs share distant ancestry with shrews (family Soricidae), with gymnures possibly being the intermediate link, and have changed little over the last 15 million years. Like many of the first mammals, they have adapted to a nocturnal, insectivorous way of life. Hedgehogs’ spiny protection resembles that of the unrelated rodent porcupines and monotreme echidnas.
The name hedgehog came into use around the year 1450, derived from the Middle English heyghoge, from heyg, hegge (“hedge”), because it frequents hedgerows, and hoge, hogge (“hog”), from its piglike snout. Other names include urchin, hedgepig and furze-pig. The collective noun for a group of hedgehogs is array or prickle.