Thanks to the sparse population of the forest and the filter action of bunter sandstone, many springs and streams in the hills have retained their natural water quality, so that they remain healthy habitats for many species of fish. These include brown trout and brook lamprey and, in calmer waters, minnow, spined loach and stone loach. In larger meadow streams grayling, perch, pike, burbot und various other minnow-like species may be found. Dragonflies, such as the golden-ringed dragonfly and the otherwise rare northern damselfly, may often be seen by streams and ponds.