Animal life in The Netherlands is relegated by region according to vegetation. Seabirds and other sea life, such as mollusks, are found especially in the muddy Waddenzee area and in the extreme southwest. Migrating birds pass in huge numbers through the Netherlands or remain for a summer or winter stay. Species of waterbirds and marsh and pasture birds are numerous. Larger mammals, such as roe deer, red deer, foxes, and badgers, are mostly restricted to nature reserves. Some species, such as boars, beavers, fallow deer, mouflons, and muskrats, have been introduced locally or reintroduced. Some reptiles and amphibians are endangered. Numerous species of river fish and river lobsters have become scarce because of water pollution. There is a diversity of brackish and freshwater animals inhabiting the many lakes, canals, and drainage ditches, but the vulnerable species of the nutritionally deficient waters have become rare.
Nature reserves have been formed by governmental and private organizations. Well-known reserves include the Naardermeer of Amsterdam, the Hoge Veluwe National Park, and the Oostvaardersplassen in the centre of the country. Some endangered species are protected by law.
