Natural History of the Racer
Coluber constrictor
BY
HENRY S. FITCH
Throughout much of the United States the racer is abundant and is one of the snakes best known to man. Its active diurnal habits and its preference for a habitat in meadows, pastures, and hayfields rather than in remote wilderness areas, result in frequent encounters with humans. The racer is a predator on many kinds of small animals, both vertebrates and invertebrates; it takes as food chiefly animals that are agricultural pests but also destroys some beneficial kinds. Yet, in general, the attitudes of rural people toward the racer are little influenced by these economic and ecologic considerations, but rather, are dominated by an unreasonable fear, despite the racer's inoffensive disposition, and inability to inflict any harm on humans.
Although an extensive literature exists regarding the racer, no thorough study of the species' natural history has been made heretofore. Obviously such study is needed. Few species of vertebrates having comparable economic bearing have been similarly neglected. In 1948, undertaking a program of ecological research on the recently created University of Kansas Natural History Reservation, I included the racer among the many common species studied to gain insight into the functioning of the local ecosystem. Live-trapping of snakes on the area was begun in 1949, and these operations were greatly intensified in the years 1957 through 1962, with efforts concentrated on the study of the racer in the 1960, 1961 and 1962 seasons. Thus my study is based upon 14 consecutive years' records on the Reservation, the northeasternmost section in Douglas County, Kansas, six and one-half miles north northeast of the University of Kansas campus at Lawrence. After the acquisition in 1956 of the 160-acre Rockefeller Tract adjacent to the Reservation on the north in Jefferson County, field work was extended to this new area, which, because it was superior habitat, in the final years of the study produced more records than the Reservation. An important but relatively minor segment of the data originated from Harvey County Park, 13 miles west of Newton, Kansas, where lines of live-traps were maintained in 1959, 1960, 1961, 1962. Smaller collections of data were obtained from the Lalouette Ranch in the Flint Hills, three miles northeast of Florence, Marion County, Kansas, and from Cedar Bluff Reservoir, 23 miles west and seven miles south of Hays in Trego County, western Kansas, where live-trapping was carried on in 1959 and 1960. Additional data were obtained on numerous field trips to various collecting localities in northeastern Kansas. My first-hand knowledge of the species is also based, in part, on many years of field experience with the far western subspecies C. c. mormon in western Oregon and California, and on similar experience in 1947 and 1948 with the southern subspecies, C. c. anthicus in central Louisiana.
This varied field experience with the species at localities well scattered throughout its geographic range has added perspective to the study even though most of the records were collected within a radius of three quarters of a mile. No one locality can be regarded as entirely typical of a species' habitat over its range as a whole. According to my philosophy, the ecological niche of a species is subject to geographical variation analogous to the variation to be seen in the morphological characters of the animal itself. Different community associates, including different competitors, prey, and predators, and different physical factors enforce a somewhat different way of life on a species in geographically remote parts of its range. When analyzed these differences often turn out to have a genetic basis. Thus, limits of tolerance to heat, cold, and drought often vary geographically, and the population density, reproductive potential, seasonal cycle, and other properties of populations may be altered either by the direct effect of the environment, or through its effect on the genetic constitution, produced by natural selection.