Bohn Lake State Natural Area (Town of Deerfield, Wisconsin)

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Bohn Lake is a 13-acre, 24-foot deep hard-water seepage lake that is part of a geologically significant tunnel channel. Often part of a larger tunnel valley system, a tunnel channel is a large cavern created by a meltwater river flowing beneath the glacial ice. As a seepage lake, the Bohn Lake shoreline fluctuates anywhere from four to six feet depending on the hydrologic cycle and in some dry years contains little water. In wet years, abundant vegetation grows in distinctive concentric rings around the lake due to its fluctuating nature. Each ring has a different combination of species including numerous sedges, spike rushes, bulrushes, panic grasses, and silverweed. The lake also contains an abundance of floating leaved aquatics such as water-lilies. The uplands, especially those to the north, contain formerly grazed but highly restorable savanna. Many spring-blooming savanna indicators are present including shooting star and puccoon. Other plants include New Jersey tea, lance-leaved ground-cherry, Canadian milk-vetch, round-headed bush-clover, and hoary vervain. Animal life is diverse with birds such as turkey, tree swallow, northern oriole, great-crested flycatcher, eastern wood pewee, chipping sparrow, eastern bluebird, red-eyed vireo, and wood thrush. Numerous invertebrates also use the area and include white-faced pondhawk dragonfly and pearl crescent, red admiral, and banded hairstreak butterflies. Bohn Lake is owned by the DNR and was designated a State Natural Area in 2008.