This is the collected wisdom gathered from previous answers to this peculiar question: Newt, Nutria, Noolberger, Narwhal, Nilgai, Numbat, Nightjar, Nautilus, Natterjack toad, Nepal tiger, Newfoundland dog, New Forest pony, Nightingale and -- you can take ot ;leave these ones -- Nellie the Elephant, Ninja Turtles, a nelephant and a nostrich!
Message to comloulou (sorry oliviac for generating another email!): comloulou, if a question annoys you because someone else asked it before, why not just ignore it?
(nb oliviac: comloulou and I are regulars on this site and have seen this question asked many times before, though no-one has been able to explain why so many people are interested in it! Please tell us - is it part of a quiz or something?)