=====+=================================+=================================
| Original record | Record(s) of recapture
+---------------+--------+--------+---------------+--------+--------
| | Snout- | | | Snout- |
Sex | | vent | | | vent |
| Date | length,| Weight,| Date | length,| Weight,
| | milli- | grams | | milli- | grams
| | meters | | | meters |
-----+---------------+--------+--------+---------------+--------+--------
[M] | Aug. 17, 1959 | 223 | 5.3 | Sept. 12, 1960| 503 | 42
[F] | Oct. 26, 1959 | 278 | 10 | Oct. 26, 1959 | 566 | 55
[F] | Nov. 2, 1959 | 340 | 18 | May 11, 1961 | 582 | 65
[F] | Nov. 10, 1959 | 348 | 13.7 | June 20, 1961 | 733 | 127
[F] | Oct. 19, 1952 | 361 | 15.3 | Oct. 9, 1953 | 620 | 68
[M] | May 9, 1953 | 368 | 17 | May 13, 1954 | 609 | 84
[F] | April 16, 1950| 328 | 142 | Oct. 10, 1950 | 603 | 78.2
[F] | May 17, 1956 | 358 | 15.2 | Oct. 6, 1956 | 575 | 52
[M] | 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
Column headings:
A: Snout-vent length in mm.
B: Weight in grams
C: Probable age in months
====+=================================+==================================
| Original record | Record(s) of recapture
Sex +---------------+-----+----+------+--------------+-----+-----+-------
| Date | A | B | C | Date | A | B | C
----+---------------+-----+----+------+--------------+-----+-----+-------
[M] | Nov. 12, 1952 | 342 |....| 2-1/2| May 20, 1955 | 702 | 110 | 33
[M] | Nov. 1, 1953 | 330 | 11 | 2 | Aug. 16, 1956| 780 | 162 | 35-1/2
[M] | Nov. 12, 1953 | 293 |....| 2-1/2| May 14, 1956 | 634 | 96 | 32-1/2
| | | | | Oct. 13, 1956| 689 | 110 | 37-1/2
[M] | April 15, 1955| 320 | 13 | 9-1/2| June 8, 1958 | 740 | 118 | 45
[M] | Oct. 2, 1955 | 348 | 18 | 1 | May 22, 1958 | 728 | 120 | 33
| | | | | May 21, 1960 | 795 | 130 | 57
[M] | June 25, 1959 | 378 | 10 | 10 | June 30, 1960| 590 | 60 | 22
| | | | | June 7, 1961 | 705 | 123 | 33
[M] | 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
Column headings:
A: Snout-vent length in mm.
B: Weight in grams
C: Probable age in months
====+==================================+====================================
| Original record | Record(s) of recapture
Sex +--------------+-----+-----+-------+---------------+-----+------+-------
| Date | A | B | C | Date | A | B | C
----+--------------+-----+-----+-------+---------------+-----+------+-------
[M] | Oct. 6, 1960 | 595 | 80 | 13 | July 23, 1961 | 650 | 70 | 23
[M] | Oct. 13, 1950| 525 | 52.6| 13-1/2| Oct. 2, 1951 | 675 | 105 | 25
[M] | Nov. 2, 1950 | 545 | 55.6| 14 | Oct. 24, 1951 | 670 | 100 | 26
[M] | Sept. 2, 1957| 522 | 57 | 12 | Oct. 14, 1958 | 690 | 103 | 25-1/2
[M] | Oct. 17, 1953| 558 | 47 | 13-1/2| May 10, 1955 | 718 | .... | 32
[M] | Nov. 14, 1956| 587 | 57 | 14-1/2| May 20, 1958 | 728 | 100 | 52-1/2
| | | | | June 17, 1959 | 880 | 219 | 64-1/2
[M] | Sept. 7, 1959| 533 | 45 | 12 | June 6, 1961 | 740 | 112 | 33
[M] | Oct. 17, 1959| 558 | 56 | 13-1/2| July 21, 1960 | 625 | 63 | 22-1/2
| | | | | June 7, 1961 | 670 | 95 | 33
[M] | Oct. 16, 1952| 577 | 62.0| 13-1/2| May 31, 1955 | 809 | 160 | 45
| | | | | May 11, 1956 | 855 | 144.3| 56-1/2
[M] | Oct. 11, 1950| 570 | 65.9| 13-1/2| July 11, 1956 | 820 | 193.6| 82-1/2
[M] | Oct. 14, 1953| 560 | 52 | 13-1/2| June 29, 1958 | 794 | 256 | 70
[M] | Oct. 6, 1950 | 563 | 55.8| 13 | Sept. 28, 1958| 907 | 243 | 109
[M] | Oct. 14, 1953| 523 | 44 | 13-1/2| May 19, 1959 | 818 | 190 | 80-1/2
| | | | | May 17, 1960 | 850 | 211 | 92-1/2
[M] | Oct. 13, 1953| 521 | 50.1| 13-1/2| May 13, 1958 | 814 | 166.4| 44-1/2
| | | | | June 3, 1959 | 826 | 165 | 47
[M] | Nov. 5, 1953 | 512 | 34 | 14 | May 22, 1958 | 847 | 135 | 69
[F] | Aug. 11, 1953| 534 | 39.2| 11-1/2| Sept. 18, 1954| 670 | 143 | 24-1/2
[F] | Oct. 14, 1949| 588 | 55.2| 13-1/2| Oct. 11, 1950 | 713 | 114.0| 25-1/2
[F] | Oct. 6, 1950 | 570 | 60.4| 13 | Oct. 11, 1951 | 783 | 174 | 25-1/2
[F] | Oct. 31, 1953| 582 | 58 | 14 | Oct. 5, 1954 | 860 | 195 | 25
[F] | Oct. 21, 1959| 588 | 63 | 13-1/2| May 7, 1961 | 730 | 120 | 32
[F] | May 14, 1960 | 506 | 34 | 20-1/2| Oct. 26, 1960 | 690 | 90 | 26
[M] | Oct. 22, 1960| 527 | 45 | 13-1/2| Oct. 7, 1961 | 620 | 74 | 25
[M] | May 3, 1960 | 530 | 48 | 20 | May 16, 1961 | 700 | 110 | 32-1/2
[M] | 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.
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.
[Illustration: 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
=====================+=============+=============+========+==========
| Snout-vent | Tail length | Weight | Probable
Date of Capture | length in | length in | in | age in
| millimeters | millimeters | grams | months
---------------------+-------------+-------------+--------+----------
_No. 1, male_ | | | |
October 21, 1953 | 676 | 216 | 85 | 25-1/2
October 12, 1954 | 733 | 238 | 128 | 37-1/2
July 31, 1955 | 755 | 243 | 143 | 46
May 20, 1956 | 785 | 250 | 153 | 55-1/2
July 15, 1957 | 788 | 252 | 162 | 69-1/2
June 30, 1958 | 820 | 264 | 200 | 81
May 15, 1959 | 828 | 263 | 195 | 91-1/2
May 14, 1960 | 840 | 265 | 195 | 103-1/2
_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 | 92-1/2
July 16, 1960 | 890 | 257 | 190 | 94-1/2
_No. 3, male_ | | | |
May 26, 1955 | 565 | 171 | 53 | 21
August 28, 1957 | 798 | 245 | 155 | 48
May 13, 1958 | 814 | 249 | 137 | 56-1/2
May 4, 1959 | 848 | 252 | 180 | 68
June 12, 1961 | 896 | 262 | 198 | 93-1/2
_No. 4, male_ | | | |
May 19, 1956 | 632 | 208 | 78 | 20-1/2
August 2, 1957 | 740 | 238 | 123 | 35
May 20, 1959 | 796 | 246 | 132 | 56-1/2
May 23, 1960 | 813 | 280 | 140 | 68-1/2
_No. 5, male_ | | | |
June 30, 1956 | 594 | 188 | 73 | 22
October 12, 1956 | 658 | 200 | 80 | 27-1/2
July 14, 1957 | 690 | 220 | 102 | 34-1/2
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 | 13-1/2
July 19, 1957 | 673 | 218 | 96 | 22-1/2
May 5, 1960 | 780 | 250 | 175 | 56
May 9, 1961 | 840 | 272 | 272 | 68
_No. 7, female_ | | | |
May 12, 1957 | 790 | 238 | 175 | 32-1/2
September 3, 1957 | 810 | 243 | 208 | 36
October 1, 1958 | 883 | 259 | 206 | 49
July 11, 1959 | 915 | 247[A] | 190 | 58-1/2
September 12, 1960 | 930 | 249[A] | 238 | 72-1/2
September 14, 1961 | 1012 | 268[A] | 332 | 84-1/2
_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.
[Illustration: Fig. 19. Graph from records of blue racers marked early
in life and recaptured, showing average and extreme weights in samples
of different ages. Early in life the females outstrip males in growth
and the size differential increases throughout life.]
A few adult racers recaptured, including different individuals of
small, medium, and large size, failed to make any measurable gain in
length over periods of months, or even over several years. Most often
the large individuals were those that failed to grow or made only
slight gains. Some of the snakes that failed to increase in length
suffered dramatic weight losses, perhaps as a result of injury,
disease, or parasitism. However, other individuals that failed to gain
appreciably in length did gain in weight. Doubtless both genetic and
environmental factors were involved. A few racers gave the impression
of being stunted by adversity. All records obtained of growth (or
failure to grow), throughout the period of my study were used in
compiling Table 17.
Table 16. Growth in Several Racers That Were Already Adult When
Originally Captured and That Subsequently Attained Unusually
Large Size
Column headings:
A: Snout-vent length in mm.
B: Weight in grams
C: Probable age in months
====+==================================+====================================
| Original record | Record(s) of recapture
Sex +--------------+-----+-----+-------+--------------+------+-----+--------
| Date | A | B | C | Date | A | B | C
----+--------------+-----+-----+-------+--------------+------+-----+--------
[M] | May 14, 1956 | 815 | 191 | 56-1/2| May 15, 1959 | 905 | 243 | 92-1/2
| | | | | May 16, 1961 | 945 | 287 | 104-1/2
[M] | May 22, 1958 | 825 | 251 | 68-1/2| June 25, 1959| 840 | 205 | 82
| | | | | May 27, 1960 | 880 | 210 | 93
| | | | | Oct. 14, 1961| 900 | 223 | 109-1/2
[M] | May 19, 1959 | 705 | 105 | 32-1/2| May 28, 1960 | 828 | ... | 45
| | | | | July 3, 1961 | 900 | 265 | 58-1/2
[F] | Nov. 6, 1954 | 823 | 190 | 38 | June 30, 1958| 1030 | 350 | 82
[F] | June 6, 1955 | 810 | 190 | 33 | May 21, 1959 | 1087 | 345 | 80-1/2
[F] | Aug. 29, 1957| 885 | 265 | 48 | Aug. 6, 1960 | 1041 | 235 | 83
[F] | May 1, 1958 | 633 | 84 | 20 | May 30, 1961 | 1088 | 320 | 57
[F] | July 20, 1958| 862 | 203 | 46-1/2| June 30, 1960| 1020 | 238 | 70
[F] | Oct. 18, 1956| 845 | 185 | 37-1/2| May 20, 1958 | 905 | 240 | 56-1/2
| | | | | Oct. 22, 1959| 1085 | 375 | 74
----+--------------+-----+-----+-------+--------------+------+-----+--------