European green toad
There aren't many birds on the island, though with the notable exception of the black guillemot. The island is home to one of Denmark's largest populations of black guillemot, a rare bird in Denmark. The other birds on the island are eurasian woodcock, western marsh harrier, common pheasant, grey partridge and common gull. The European green toad can be found on the island, and the nearby island of Samsø is the northernmost habitat for the frog in Europe. The mammals on the island are few, with only roe deer, European hare, European hedgehog, harbor seal, mice and rats. The harbour porpoise can be seen off the island's coast. The common blue butterfly is found on Tunø, though is rare in the rest of Denmark.