Natural History of the Racer Coluber constrictor

by Henry S. Fitch

Spasmodic rippling movements passed down the body of the male as he lay in contact with the female. These movements lasted several seconds, increasing in intensity, alternating with longer periods of little or no movement. As each period of vigorous writhing reached its climax, the male's head jerked forward and backward several times in seeming excitement. The female's behavior was mostly passive. She seemed to be receptive, but from time to time, without any noticeable warning, she darted away for several feet as she had when the pair was first discovered. Each time the male darted forward with her, maintaining contact while she moved. These swift movements of the female seemed to be spontaneous, at least in most instances there was no evident cause for alarm. The female's movements seemed to stimulate the male's interest rather than to discourage him. In most instances the female moved only four to five feet, then stopped abruptly or turned back. She would stop in a loose resting coil, in thick grass, with the male lying over her. Often she coiled in such a way that the posterior end of her body was beneath her forebody, but this did not seem to deter the male from moving the posterior end of his body into position beside hers. After a sudden change in the female's position, the rear of the male's body would perform groping movements along that of the female until his cloacal region was approximately opposite hers. The male sometimes had his chin pressed against the female's back, especially when he was moving forward along her, but more often his head was raised, and frequently was as much as 18 inches from the female's head.

At intervals averaging approximately ten minutes, during a little more than an hour of observation, the male would suddenly dart away from the female, and with unusually rapid and animated movements, he would move around her in an irregular and devious course, sometimes as far as five feet away, but usually within 18 inches. Usually on each such expedition several or many circuits were made; then the male would return to the female and would glide rapidly along her until he attained the mating position. A period of especially vigorous courting movements would follow.

At 12:55 p. m. it was necessary for me to discontinue observations, and I left the female confined in a cloth bag. Returning at 1:20 p. m. I found that the male was not displaying interest in the female confined in the bag, nor in the other female loose in the enclosure. The first female was released from the bag, and was out of sight for approximately four minutes. When relocated she was again attended by the male, who was carrying on courtship even more vigorously than he had before. At 1:35 p. m. the male achieved intromission. Although the pair was under observation at the time intromission occurred, the actual eversion of the hemipenis was not seen because the snakes were partly concealed by dense vegetation. There was a sudden flurry of movement, the male's head waving and his body thrashing. In an instant these violent movements subsided, and after a few seconds the female began to crawl forward slowly. The male had relaxed, and relinquished his contact with the female anteriorly. As she moved away he was dragged after her tail-first. He made slight backward wriggling movements that perhaps aided in maintaining sexual contact. The female's restlessness increased, and in eight minutes she dragged the male in a circuitous course a distance estimated to be between 20 and 30 feet. At 1:40 p. m. the pair was ten feet from the point where copulation had begun. The female showed increasing inclination to climb, raising her head and forebody against the trunks of saplings, and finally reaching up one to a branch 20 inches above the ground, and climbing first along the branch and then farther up the main trunk. As she progressed the male was lifted from the ground, dangling limply suspended by his hemipenis and its base had become exposed. At 1:43 p. m. separation occurred and the male dropped into the grass. Semen dripped from the cloacae of both snakes. That from the female was tinged with blood. The individuals involved in this observation were kept in the enclosure subsequently but no further sexual behavior was noted.

Contrary to the popular belief that these racers have permanent mates, all available evidence indicates that they are promiscuous, and two or more males may simultaneously court the same female in the brief spring breeding season. On May 24, 1960, while I was walking in a hilltop field of brome grass, a sudden movement attracted my attention to three racers lying alongside each other. Only the posterior parts of their bodies and their tails were visible. Two were males and were performing the characteristic slow writhing movements against the body of the female from either side. Although the heads were not in view, the snakes may have been able to see me through the screening vegetation; after I had watched for approximately 20 seconds, all three suddenly took alarm, for no apparent cause, and scattered.

Further evidence of promiscuity is provided by the account of Ellicott (1880:207) who wrote regarding the eastern subspecies: "I noticed a ball of black snakes (Bascanion constrictor L) rolling slowly down a steep and stony hillside ... about two miles above Union Factory, Baltimore County, Md. ... kept together by procreative impulses." It was stated that this observation was made in early spring. "Snake balls" have often been observed, and described in the literature; usually the snakes involved were garter snakes (Thamnophis) or water snakes (Natrix). Seemingly, typical aggregations consist of a single adult female and several or many males attempting to mate with her. There is a distinct possibility that the snakes involved in Ellicott's observations were misidentified.

Sexual behavior of the racer is in most respects remarkably similar to that of the common garter snake, Thamnophis sirtalis, well known through the work of Blanchard and Blanchard (1942). In studying sexual behavior of racers, several observers have failed to differentiate between the different stages of the mating process, and have assumed that copulation was occurring when actually only the precopulatory behavior was observed. In an early description of courtship in this racer in Kansas, Brons (1882:365) stated that the female "at times, seems to toy with the male, indisposed to yield to his importunities, though pressed with ardor. To avoid his suit, at times, she will dart through grass, among stones, or enter a crevice. Should he be able to reach his mate while within a hole, he is not slow in bringing her to the surface, again to be repulsed. Upon an unbroken ground the sexual union is less prolonged. Here she is unable to free herself from his quick and effectively directed moves. In case she attempts to quit him, a coil is thrown about her body, and his head laid flat upon her neck, and replaced as promptly as dislodged, evidently in the endeavor to propitiate her."

Another account probably based on courtship rather than copulation is that of Wright and Wright (1957:135), who described the behavior of a pair of C. c. priapus on Billy Island, Okefinokee Swamp in southern Georgia, on May 8, 1921, as follows: "They were stretched out, more or less coiled ... the rear parts of the bodies from the vent were entwined. The female, or smaller one seemed to have its tail around that of the male. There were contortions or quiverings from time to time.... May 8, 1921: Jackson Lee saw black snakes entwined, the male seizing the female by the top of the neck."

Blanchard and Blanchard (op. cit.) have described the dragging of the male by the female during coitus in the garter snake, and the temporarily inseparable bond formed between members of a pair by the recurved spines of the engorged hemipenis, but it has not been generally recognized that the process is much the same in other colubrines. Cottam (1937:229) described and photographed mating in a pair of C. c. mormon in Utah. The copulating racers were shown in a loose coil lying alongside each other with tails intertwined. However, when disturbed by the observers, these racers made frantic efforts to escape, crawling in a spiral course, while remaining attached and intertwined, "with no evident attempt to separate" during approximately a quarter hour of observation.

The racer is notorious for its aggressive behavior and occasional alleged attacks on humans in the breeding season. The tendency has doubtless been much exaggerated, especially in the verbal second- or third-hand accounts based on the alleged observations of eye-witnesses. Nevertheless, the supposition that large adults will sometimes pursue or attack humans when disturbed is well substantiated. In most of the instances known to me, it is the large eastern subspecies, C. c. constrictor, involved in these incidents, and seemingly the smaller racers of the Middle West, far West and South are less inclined to behave aggressively. In May 1958 two pairs of large racers were confined in a semicircular wire enclosure thirty feet across and open on top, and with natural vegetation, at the Reservation headquarters. Often in approaching the cage I saw two or more racers in close association, but because of sheltering vegetation, and the snakes' timidity observation was difficult. On May 19 a pair were lying partly extended in loose coils, but immediately the female took alarm and darted away, breaking loose from the male; his hemipenis was exposed, and underwent involution and retraction in approximately 30 seconds. Unlike the female, the male on this occasion did not attempt to escape, but turned to face me with a show of aggressiveness. Probably copulation was in its final stages when the disturbance occurred.

Circling of the female racer by the male from time to time in the course of courtship has not been recognized by previous observers as a part of the mating pattern, but Pope (1944:171) described somewhat analogous behavior, probably modified by unnatural conditions of captivity and the crowding of many racers in one cage. Pope, citing earlier observations by Noble, wrote: "When sexually excited, the male blacksnakes dash wildly about before paying court to individual females. In captivity these dashes excite all specimens confined together. A male, after picking out a mate, moves his chin lightly along her back, while undulations run forward along his sides and he extends his tongue now and then. Later he throws the part of his body near his vent over the corresponding part of the female, the two tails sometimes becoming loosely intertwined."