| Kinds of prey and their percentage frequencies in in samples | Snout-Vent Length (mm.) of Racers in Sample | ||||||||
| 200 299 | 300 399 | 400 499 | 500 599 | 600 to 699 | 700 to 799 | 800 to 899 | 900 to 999 | 1000 to 1099 | |
| gryllid cricket | .40 | .39 | .11 | .25 | .23 | .15 | .15 | .12 | .08 |
| Melanoplus | .09 | .14 | .14 | .14 | .15 | .20 | .27 | .25 | |
| Ceuthophilus | .20 | .11 | .13 | .06 | .07 | .12 | .09 | .04 | |
| Orchelimum | .04 | .02 | .01 | .01 | .01 | ||||
| tettigoniid | .03 | .02 | .06 | .03 | .02 | .05 | |||
| "other grasshopper" and miscellaneous orthopteran | .30 | .25 | .10 | .09 | .03 | .12 | .07 | .09 | |
| Arphia simplex | .03 | .02 | .05 | .08 | .08 | .04 | .09 | ||
| miscellaneous insect | .04 | .04 | .09 | .07 | .04 | .08 | .05 | .04 | |
| lizard | .20 | .09 | .18 | .09 | .07 | .11 | .01 | .01 | |
| snake | .20 | .07 | .06 | .05 | .04 | .05 | .08 | .12 | |
| Microtus | .04 | .02 | .08 | .13 | .09 | .12 | .25 | ||
| Peromyscus | .09 | .02 | .05 | .06 | .03 | .05 | .04 | ||
| "other mammal" | .01 | .04 | .10 | .03 | .03 | ||||
| bird | .01 | .01 | |||||||
| Total prey items for size group | 5 | 23 | 28 | 101 | 120 | 121 | 127 | 76 | 24 |
The wide disparity in size between young and adult racers also results in utilization of different food sources to some extent. In some kinds of snakes adults and young draw their food from entirely different sources, but in the racer there is broad overlap, as shown in [Table 6]. The samples from the largest and smallest size groups of racers are relatively small. Two important kinds of prey—voles and grasshoppers of the genus Melanoplus—were not found at all in the smallest size groups of snakes and comprised increasing percentages in the food of the larger size groups. A large adult vole is too large to be swallowed except by an unusually large racer, and a young vole old enough to leave its nest is far too large for a hatchling racer. Grasshoppers of the genus Melanoplus are relatively large and heavily armored, and so are relatively immune to attacks from the smaller snakes. Small soft-bodied orthopterans including Gryllus, Ceuthophilus and Orchelimum, and also lizards and snakes, are best represented in the food of the smaller racers. Other types of prey showed no definite correlation with size of the racer taking them.
Many observers have published accounts of the courtship and/or mating of the racer, but all of these are, to some degree, incomplete. Because of the widely different circumstances, and the different viewpoints of the observers involved, the several accounts give much different impressions of sexual behavior in this species. Either singly or combined, the published accounts do not provide an adequate description of the process.
My own observations, made both under natural conditions and in large outdoor enclosures, are likewise somewhat incomplete, but indicate that the whole sequence of courtship and mating is divisible into the following well-defined stages: 1) the finding of a receptive female by the male; 2) the persistent following of the female by the male, who courts her by lying extended along her body and performing writhing movements, with periodic interruptions during which he momentarily leaves the female and courses rapidly through the grass around her; 3) the acceptance of the male by the female, signalled by the raising of her tail and the almost instantaneous intromission; 4) the dragging of the passive male by the female while he is firmly attached to her during the period of coitus; 5) separation of the pair and involution of the male's hemipenis.
Even in the breeding season, racers that were confined in enclosures usually were either indifferent to each other or responded with reactions of fear or hostility. In moving they tended to follow the edges, and often two moving in opposite directions would approach each other; when this occurred, one snake might strike at the other with a short jab that seemed to be mostly bluff, and then would dart away. The males, being smaller, were usually the more wary.
Sexual behavior was noticed on only a few occasions. Several large adult males were less wary than others and usually manifested curiosity or interest toward other racers. My most complete observations of sexual behavior were made on May 18, 1962, when a newly caught adult male was added to an enclosure of 100-foot circumference already containing several racers, two of which were large adult females. Within half an hour the male was found courting one of the females. She was lying in a loose coil, with the male extended along her. At my approach the female darted away in alarm for approximately three feet, and the male moved with her, so swiftly and adroitly that he maintained contact and was in approximately his original position with respect to the female when she stopped.