Natural History of the Racer Coluber constrictor

by Henry S. Fitch

Relatively few individual racers were recaptured after periods of several years. Each of the eight listed in [Table 15] is among those that were captured in four or more different years, and their records are significant in revealing the trend of growth after sexual maturity has been attained. These snakes, one to three years old at the time they were marked, show well the persistent but decreasing growth, and the fluctuating weight that is characteristic of this and other species.

Fig. 18. Graph from records of blue racers marked early in life and recaptured, showing average and extreme snout-vent lengths for males and females of various ages. Growth is especially rapid in the first year, but continues, with gradual slowing, throughout life. In hatchlings, the sexes are of approximately equal size, but females grow to be markedly larger than males.

Some of the largest racers recorded had already reached unusually large size when they were first captured, so there was no opportunity to determine their ages. Several others, originally captured as small- or medium-sized adults, subsequently grew to a size approaching the maximum, and thus provided a basis for estimating the ages of large individuals. The records of nine such racers are listed in [Table 16].

Table 15. Changes in Lengths and Weights
in Eight Racers Recaptured Repeatedly Over Periods of Years

Date of Capture	Snout-vent length in millimeters	Tail length length in millimeters	Weight in grams	Probable age in months
No. 1, male
October 21, 1953	676	216	85	251/2
October 12, 1954	733	238	128	371/2
July 31, 1955	755	243	143	46
May 20, 1956	785	250	153	551/2
July 15, 1957	788	252	162	691/2
June 30, 1958	820	264	200	81
May 15, 1959	828	263	195	911/2
May 14, 1960	840	265	195	1031/2
No. 2, male
May 9, 1955	678	212	105	32
May 26, 1958	827	248	195	69
May 3, 1959	865	262	218	80
May 14, 1960	877	264	218	921/2
July 16, 1960	890	257	190	941/2
No. 3, male
May 26, 1955	565	171	53	21
August 28, 1957	798	245	155	48
May 13, 1958	814	249	137	561/2
May 4, 1959	848	252	180	68
June 12, 1961	896	262	198	931/2
No. 4, male
May 19, 1956	632	208	78	201/2
August 2, 1957	740	238	123	35
May 20, 1959	796	246	132	561/2
May 23, 1960	813	280	140	681/2
No. 5, male
June 30, 1956	594	188	73	22
October 12, 1956	658	200	80	271/2
July 14, 1957	690	220	102	341/2
June 23, 1958	749	226	136	46
July 24, 1959	751	239	133	59
May 27, 1960	765	235	130	69
No. 6, male
October 19, 1956	518	167	43	131/2
July 19, 1957	673	218	96	221/2
May 5, 1960	780	250	175	56
May 9, 1961	840	272	272	68
No. 7, female
May 12, 1957	790	238	175	321/2
September 3, 1957	810	243	208	36
October 1, 1958	883	259	206	49
July 11, 1959	915	247[A]	190	581/2
September 12, 1960	930	249[A]	238	721/2
September 14, 1961	1012	268[A]	332	841/2
No. 8, female
June 23, 1955	601	175	67	22
August 3, 1958	920	255	300[B]	60
July 23, 1959	955	281	211	71
May 18, 1960	962	262	260	81

[A] Incomplete.

[B] With food.