Natural History of the Racer Coluber constrictor

by Henry S. Fitch

Sex	Original record			Record(s) of recapture
	Date	Snout-vent length, millimeters	Weight, grams	Date	Snout-vent length, millimeters	Weight, grams
♂	Aug. 17, 1959	223	5.3	Sept. 12, 1960	503	42
♀	Oct. 26, 1959	278	10	Oct. 26, 1959	566	55
♀	Nov. 2, 1959	340	18	May 11, 1961	582	65
♀	Nov. 10, 1959	348	13.7	June 20, 1961	733	127
♀	Oct. 19, 1952	361	15.3	Oct. 9, 1953	620	68
♂	May 9, 1953	368	17	May 13, 1954	609	84
♀	April 16, 1950	328	142	Oct. 10, 1950	603	78.2
♀	May 17, 1956	358	15.2	Oct. 6, 1956	575	52
♂	Nov. 1, 1953	330	11	May 21, 1955	674	92

Though covering a wide size-range, the young of the year entering hibernation are still a distinct size group, not yet overlapping that of the next older group of young. Growth during the first year of life is best shown by the individuals in [Table 12], all of which were marked either before their first hibernation or soon after emerging from it, and were recaptured either the following autumn, or in spring soon after emerging from a second hibernation.

These records indicate that the young racers at the time of their second hibernation have grown to a snout-vent length of well over 500 millimeters, but less than 700 millimeters, and a weight of more than 40 grams but less than 100 grams. Other racers marked in the first few weeks of life were recaptured after two or more seasons of growth, and indicate the sizes that may be expected in young adults from two to five years old, as shown in [Table 13].

Table 13. Growth of Racers Marked at an Age of Less Than One Year
and Recaptured in Their Second, Third or Fourth Years

Sex	Original record				Record(s) of recapture
	Date	Snout-vent length in mm.	Weight in grams	Probable age in months	Date	Snout-vent length mm.	Weight in grams	Probable age in months
♂	Nov. 12, 1952	342	....	21/2	May 20, 1955	702	110	33
♂	Nov. 1, 1953	330	11	2	Aug. 16, 1956	780	162	351/2
♂	Nov. 12, 1953	293	....	21/2	May 14, 1956	634	96	321/2
					Oct. 13, 1956	689	110	371/2
♂	April 15, 1955	320	13	91/2	June 8, 1958	740	118	45
♂	Oct. 2, 1955	348	18	1	May 22, 1958	728	120	33
					May 21, 1960	795	130	57
♂	June 25, 1959	378	10	10	June 30, 1960	590	60	22
					June 7, 1961	705	123	33
♂	Nov. 1, 1953	330	11	2	Aug. 25, 1957	805	183	48

Unlike young of the year, racers in their second autumn were trapped in large numbers. By this time all were large enough to be caught in the traps of quarter-inch wire mesh, and they were the most abundant size group. Many that were marked at this stage were recaptured after intervals of months or years, showing the trend of growth. Some of these snakes in their second autumn already had overtaken the more retarded third-year individuals. The two age classes cannot be separated with certainty. Selected records of individuals that were almost certainly second-year young at the time they were marked are presented in [Table 14].

Table 14. Growth of Young Racers That Were Marked Near the Time of Their Second Hibernation

Sex	Original record				Record(s) of recapture
	Date	Snout-vent length in mm.	Weight in grams	Probable age in months	Date	Snout-vent length in mm.	Weight in grams	Probable age in months
♂	Oct. 6, 1960	595	80	13	July 23, 1961	650	70	23
♂	Oct. 13, 1950	525	52.6	131/2	Oct. 2, 1951	675	105	25
♂	Nov. 2, 1950	545	55.6	14	Oct. 24, 1951	670	100	26
♂	Sept. 2, 1957	522	57	12	Oct. 14, 1958	690	103	251/2
♂	Oct. 17, 1953	558	47	131/2	May 10, 1955	718	....	32
♂	Nov. 14, 1956	587	57	141/2	May 20, 1958	728	100	521/2
					June 17, 1959	880	219	641/2
♂	Sept. 7, 1959	533	45	12	June 6, 1961	740	112	33
♂	Oct. 17, 1959	558	56	131/2	July 21, 1960	625	63	221/2
					June 7, 1961	670	95	33
♂	Oct. 16, 1952	577	62.0	131/2	May 31, 1955	809	160	45
					May 11, 1956	855	144.3	561/2
♂	Oct. 11, 1950	570	65.9	131/2	July 11, 1956	820	193.6	821/2
♂	Oct. 14, 1953	560	52	131/2	June 29, 1958	794	256	70
♂	Oct. 6, 1950	563	55.8	13	Sept. 28, 1958	907	243	109
♂	Oct. 14, 1953	523	44	131/2	May 19, 1959	818	190	801/2
					May 17, 1960	850	211	921/2
♂	Oct. 13, 1953	521	50.1	131/2	May 13, 1958	814	166.4	441/2
					June 3, 1959	826	165	47
♂	Nov. 5, 1953	512	34	14	May 22, 1958	847	135	69
♀	Aug. 11, 1953	534	39.2	111/2	Sept. 18, 1954	670	143	241/2
♀	Oct. 14, 1949	588	55.2	131/2	Oct. 11, 1950	713	114.0	251/2
♀	Oct. 6, 1950	570	60.4	13	Oct. 11, 1951	783	174	251/2
♀	Oct. 31, 1953	582	58	14	Oct. 5, 1954	860	195	25
♀	Oct. 21, 1959	588	63	131/2	May 7, 1961	730	120	32
♀	May 14, 1960	506	34	201/2	Oct. 26, 1960	690	90	26
♂	Oct. 22, 1960	527	45	131/2	Oct. 7, 1961	620	74	25
♂	May 3, 1960	530	48	20	May 16, 1961	700	110	321/2
♂	May 27, 1961	535	40	21	Oct. 25, 1961	672	98	26

From the records in [Table 14] and many more like them, average and extreme sizes for progressively older age groups were estimated. Even racers that were already of adult size when they were marked were tentatively identified with one or another age group, and their records of subsequent growth were used. Most of the records show that the females grow more rapidly than the males, and are, on the average, larger at any given age.