Since 2008, both the quantity and number of bird species has seen an increase, and now between 20 and 30 species breed on Peberholm regularly. The island is largely inhabited by several kinds of breeding gulls, and some locally threatened species have also found a home here as breeders, including the Mediterranean gull and European rock pipit in some years. Many geese, ducks, Great cormorants, and waders rest on the small island and the White-tailed eagle is often observed here in winter. The European green toad, which is rare and protected in Denmark, was found living in several ditches. In 2007–08 a count found c. 2,500 individuals, which is among the largest populations in Scandinavia. It is assumed that toads from Saltholm have swum across. Three species of mice have also populated Peberholm, from very early on, and since 2010, hares have crossed the ice from Saltholm as well and are now breeding on Peberholm. It is important to keep these populations under surveillance, as mice in particular are known to be potentially dangerous to the rails stability. From 2015, white rabbits too have been seen. They are assumed to have been released from someone's car.