Like, when they aren't dragging people into the sea or granting wishes. The wikipedia article doesn't describe in much detail about where they reside. Holes? Mountain Tops? Tiny Cottages?
In his collection of Irish fairy and folk tales, W.B. Yeats offered an 18th-century poem by William Allingham titled "The Lepracaun; Or, Fairy Shoemaker" which describes the sound:
Lay your ear close to the hill. Do you not catch the tiny clamour, Busy click of an elfin hammer, Voice of the Lepracaun singing shrill As he merrily plies his trade?
This would imply that the Leprechaun, like many other fey of Irish mythology, lives in hills.