More than 2,500 plant species have been found in Ohio. The southeastern hill and valley region supports pitch pine, bigleaf magnolia, and sourwood, with undergrowths of sassafras, witch-hazel, pawpaw, hornbeam, and various dogwoods. At least 14 species of oak, 10 of maple, 9 of poplar, 9 of pine, 7 of ash, 7 of elm, 6 of hickory, 5 of birch, and 2 of beech grow in the state, along with butternut, eastern black walnut, wild black cherry, black locust, and sycamore. A relative of the horse chestnut (introduced to Ohio from Asia), the distinctive buckeye—first called the Ohio buckeye and now the official state tree—is characterized by its clusters of cream-colored flowers that bloom in spring and later form large, brown, thick-hulled nuts. Five Ohio plant species were listed as threatened in 2003, including eastern prairie fringed orchid, northern wild monkshood, and lakeside daisy; the running buffalo clover was listed as endangered that year by the US Fish and Wildlife Service.
The Buckeye State is rich in mammals. White-tailed deer, badger, mink, raccoon, red and gray foxes, coyote, beaver, eastern cottontail, woodchuck, least shrew, and opossum are found throughout the state's five wildlife districts; the bobcat, woodland jumping mouse, and red-backed mole are among many species with more restricted habitats. Common birds include the eastern great blue heron, green-winged teal, mourning dove, eastern belted kingfisher, eastern horned lark, blue-gray gnatcatcher, eastern cowbird, and a great variety of ducks, woodpeckers, and warblers; the cardinal is the state bird, and the ruffed grouse, mostly confined to the Allegheny Plateau, is a favorite game species. Bass, pickerel, perch, carp, pike, trout, catfish, sucker, and darter thrive in Ohio's lakes and streams. The snapping, midland painted, and spiny soft-shelled turtles, five-lined skink, northern water snake, midland brown snake, eastern hognose, and eastern milk snake appear throughout Ohio. The northern copperhead, eastern massasauga (swamp rattler), and timber rattlesnake are Ohio's only poisonous reptiles. Fowler's toad, bullfrog, green pickerel frog, and marbled and red-backed salamanders are common native amphibians.
Acting on the premise that the largest problem facing wildlife is the destruction of their habitat, the Division of Wildlife of the Department of Natural Resources has instituted an ambitious endangered species program. The US Fish and Wildlife Service listed 20 Ohio animal species as threatened or endangered in 2003, including the bald eagle, Indiana bat, Scioto madtom, and piping plover.