The racer dwells primarily in open situations, but as might be expected from its extensive geographic range, bringing it under the influence of diverse climates and habitats, its populations have diverged somewhat in adaptation to different environmental conditions. The eastern blacksnakes (subspecies constrictor and priapus) seem to prefer woodland and forest edge. In central Louisiana, anthicus occurs chiefly in an open type of woodland. The subspecies stejnegerianus is found chiefly in brushland and thorn forest. The western mormon is found in varied habitats, including moist streamside meadows, and chaparral. Published statements of herpetologists, based upon studies in limited areas, are briefly quoted below to show the trend of geographic change.
C. c. constrictor: This snake "occurs chiefly in fields" (Atkinson, 1901:148; Pennsylvania); "in more or less wooded regions and along hillsides and among bushes" (Surface, 1906:167, in Pennsylvania); "abundant, especially in wooded regions" (Hibbard, 1936:28, in Kentucky); "dry and more or less open places" (Conant, 1938:52, in Ohio); "old fields and areas about buildings" (King, 1939:572, in Tennessee).
C. c. priapus: In "drier parts of the [Okefinokee] swamp ... seems to prefer blueberries and saw palmettos" (Wright and Bishop, 1915:159 in Georgia); "common in grassy fields and in upland woods" (Allen, 1932:13, in Mississippi); "abundant along fence rows ... in dry pine-oak forest and in bottomland forest" (Trowbridge, 1937:296, in Oklahoma); "probably most abundant in open upland hammock or in old fields; limestone flatwoods" (Carr, 1950:80, in Florida); Oak and oak-hickory forest and small hill prairies in southern Illinois (Rossman, 1960:219).
C. c. paludicola: In "all parts of the freshwater Everglades, in cabbage palm hammocks, in salt marshes, and in mangrove swamps. On Key Largo ... in mesophytic hammock" (Duellman and Schwartz, 1958:296, in southern Florida).
C. c. anthicus: In "wooded areas in the vicinity of briar patches or other brushy undergrowth" (Clark, 1949:249, in northern Louisiana); "especially grassy uplands" (Fitch, 1949:88, in central Louisiana).
C. c. stejnegerianus: Of 291, 94 were in scattered brush, 92 in sparse brush, 41 in lightly wooded areas, 26 in grassy areas, 24 in heavy brush, eight in semi-arid places and six in heavily wooded situations (Auffenberg, 1949:55, in southern Texas).
C. c. mormon: In "thin brush skirting open prairie land" (Lord, 1866:304, British Columbia); cottonwood-willow and water margin habitats in prairie (Dice, 1916:310-312, in eastern Washington); "grass; amid water cress; bank of small ditch near meadow; barley field; sandy ground covered with rocks and driftwood; among sedges; in sagebrush; swimming in irrigation ditch" (Grinnell, Dixon and Linsdale, 1930:149, in northeastern California); low foothills, around the fields, and in the timber and brush along the canyon bottoms (Woodbury, 1931:75, in Utah); "open woods of Garry oak and poison oak, on grassy slopes, in chaparral, and in grain or hay fields" (Fitch, 1936:644, in southwestern Oregon); "low hot canyons where it was found to occupy areas having rather dry, rocky hills" (Ferguson, 1952:68, in northeastern Oregon).
C. c. flaviventris: Pastures, meadows, and fields (Hurter, 1911:170, in Missouri); "usually frequents dry open fields, although it is often found in bushes or cut-over land which has grown up into thickets" (Ortenburger, 1928:181); "pasture lands and on hill sides" (Peters, 1942:183, in Illinois); "along the levees in the salt marshes" (Liner, 1954:82, in southern Louisiana); "common in both prairie and woodland habitat" (Smith, 1947:34, in east-central Illinois); Flood plain, sand around sage-sumac brush, rocky slopes (Fouquette and Lindsay, 1955:411, in northwestern Texas).
Several observers have described the habitat in Kansas as follows: "grassy valleys and thinly wooded hillsides" (Burt, 1927:5); "moist and dry habitats, in wooded areas, and in prairies" (Smith, 1956:237); Oak-walnut hillside forest, cultivated field, buckbrush-sumac, prairie (Clarke, 1958:22).