What is Neville Longbottom's patronus?

Neville's patronus as stated in The Order of The Phoenix could only be produced inNon-corporealform, this means that the patronus only appears as mist and not like a corporeal form of a patronus when the charm becomes a spirit animal.

ThePatronus Charm(Expecto Patronum) is the most famous and one of the most powerful charm known. It is an immensely complicated and an extremely difficult spell that evokes a partially-tangible positive energy force known as aPatronus.