You can often spot roe deer in the Tyresta forests. You will also find mountain hare here as well as elk.
Foxes have made a recovery after many years of fox mange, and you sometimes see marten tracks in the winter. Smaller mammals that can be noted are the squirrel, ermine and weasel. There also are several varieties of bats in the area.
112 species of breeding birds
It is easier to spot birds than mammals, and 112 species of breeding fowl have been observed in the Tyresta area. Clearly, the most common are European robins, willow warblers and chaffinches, but less common species such as the lesser spotted woodpecker, Eurasian three-toed woodpecker, capercaillie and spotted nutcracker are here as well. The tawny owl, eagle owl and pygmy owl also can be heard in the area.
And in the lakes you can hear the characteristic call of black-throated divers.
A gold mine for wood-living insects
The primeval forest environment, with its many dying and dead trees, is a gold mine for wood-living insects, which account for a large portion of the biodiversity in the forest.
Nurseries for salmon trout
The lakes in the area harbour pike, perch, ruffe, roach and other fish. The acidic water limits the fish population.
Stensjön lake is regularly treated with lime for the benefit of salmon trout in the Åvaån river, which is very important for the stocking of waterways in Stockholm county.