Mad as a March hare

From at least the early 16th century, hares have been observed to behave in mad fashion during the month of March, which was thought to be their prime mating season. Male hares box one another for the mating rights to females and this and other wild, rushing behaviour was interpreted as March Hare Madness. In fact, the mating season for hares extends over many months in spring and therefore their seemingly mad antics are by no means confined to March. The earliest known citation of the expression in the form that we know it was Sir Thomas More The Supplication of Souls (1529) “As mad not so much as a March hare, as a mad dog.”