Writings report that in 1425 the following species of game lived in Masuria, among other life-forms: aurochses, bears, wild boars, wild horses, stags, roe deer, beavers, martens and otters.
The very last aurochs died near Lublin in 1627.
In 1698, Masuria's last wisents were killed in the course of hunting in Johannisburg Heath on the occasion of a meeting of Elector Friedrich III. of Prussia with King August II. of Poland.
The River Angerapp had been very rich in eels until the beginning of the 18th century. Then their number decreased continuously because the river was dredged.
In 1792, a hunting for wolves was organized in the Forest of Nikolaiken.
Until World War II the protected common rave was to be seen in Masuria.
Wild boars, stags, roe deer, fallow deer, foxes, hares, ermines, polecats, martens, racoons and a few elks live in the woods, as do otters, beavers and American minks by the inshore waters. Badgers, lynxes and wolves are rare.
About 200 species of birds live in Masuria. Storks' nests can be discovered in almost any Masurian village. Gulls, sea swallows, wild ducks, geese, great crested grebes, sea divers, marsh harriers, cormorants, sedge reed warblers, kingfishers and coots live on the lakes and in the bushes alongside the banks. More and more often the mute swan can be seen. Cranes, herons, bitterns and birds of prey (occasionally golden eagles and - by Lake Spirding - the legally protected sea eagles) can be found, and this is also true of ospreys, kites, buzzards, goshawks, owls, eagle owls and vultures. There are some habitats of the shy black storks, too. Furthermore, the hoopoe, woodpecker, merganser, warbler, capercaillie as well as the black and hazel grouse can be found.
The crystal-clear lakes boast of a variety of fish, crayfish and mussels. Whitefish live in Lake Rosch, Lake Mucker and in the other deep inshore waters; tench and pike in Lake Pogobin; brace in Lake Sexter; pike, eel, whitefish, pike-perch and roach in Lake Löwentin; eel, pike, perch, tench, brace and crayfish in the inshore waters of the Lyck Lake District; pike, perch, brace, tench, ukelei (Alburnus lucidus = carp fish similar to herring), whitefish, roach, eel, eel-pout, pike-perch, silurid and carp in the Great Lake Talten. There are trout in the streams of the district of Goldap. When Poland turned to the market economy the inshore waters were leased to persons interested. The new tenant fishers, however, were not interested in balanced fishing but in making quick profit. This strategy led to a reduction in the fish population.
Amphibians, such as toads and European tree frogs, small reptiles, e.g. lizards and snakes (ring snakes) and the rare European mud turtle can also be found in Masuria.
Since 2004 there has been a society called "Stork" which is active in the field of nature protection in the district of Soldau. Krestel and bat are species under protection.