Hedgehogs

In the notes titled Of the Land and Beasts of Númenor in The Nature of Middle-earth, there's an account of creatures named ekelli in Elvish. These were common in many parts of the island, and are described as 'urchins or hedgehogs of large size, with long black quills'.

The word 'urchin' here is an old word for a hedgehog, and is the source of 'sea urchin' (a spiked creature of the sea-floor with a name that literally means 'sea hedgehog'). Historically in English, 'urchin' underwent various transitions of meaning, so it is now almost never used for an actual hedgehog, but rather for a poor or ragged person, and especially a child. In fact Saruman at one point describes the Frodo and his companions as 'urchins' (The Return of the King VI 6) but there he is using the word in its modern sense (that is, he was referring to the Hobbits as small vagabonds, and not as hedgehogs!)

Worldwide, there are about twenty different species of hedgehog. Of these, the European hedgehog Erinaceus europaeus is the only kind commonly found in western Europe and the British Isles, and thus would have been the hedgehog species directly familiar to Tolkien.