Thanks to its many different landscapes, Schiermonnikoog has an abundance of plants and animals. Some sorts of animals, such as foxes, mink, weasels, moles, squirrels, deer and bats, have not been able to cross the water to the island. Most of the mammals that do live on the island, such as rabbits, hares, brown rats and hedgehogs, arrived here with human assistance. One mammal that is naturally present on Schiermonnikoog is the seal. Seals can occasionally be seen lying on the sandbank at the northwest end of the island.
There are not any reptiles on Schiermonnikoog. Among the amphibians, the most conspicuous sorts are the natterjack toad and the smooth newt.
The large variety of birds and insects more than makes up for the limited number of mammals.