The Mackinaw State Forest is home to Michigan's two most critically endangered species: the Kirtland's warbler (Setophaga kirtlandii) and Hungerford's crawling water beetle (Brychius hungerfordi). Indeed, of the five known locations in which Hungerford's crawling water beetles have been found, two are within the Mackinaw State Forest, one along the East Branch of the Black River and the other in Van Hetton Creek.
The Mackinaw State Forest is home to Michigan's two most endangered species: the Kirtland's warbler and Hungerford's crawling water beetle, with two of the five known locations for Hungerford's crawling water beetles being found within the forest.