Hatching usually occurs in late August or early September, and the
disparity in size between hatchlings and adults is greater than in
some other kinds of snakes. In 76 young from ten clutches of eggs
incubated in the laboratory, averages and extremes for measurements
and weights were as follows: snout-vent length, 214.5 (186 to 244)
millimeters; tail, 59.3 (44 to 73) millimeters; weight, 4.16 (2.4 to
5.8) grams. In each brood the size tended to be fairly uniform, except
that there were usually one or more stunted individuals markedly
smaller than the others. However, there were striking differences in
size between the young of different broods. None of the young captured
was as small as the average hatchling from the clutches incubated in
captivity, but in the 14 years of my study only four young were
captured in August. The hatchlings are relatively secretive and
elusive, and the lush vegetation of late summer provides them with
abundant hiding places. Nevertheless it is remarkable that the
hatchlings are so seldom seem, when their probable abundance is taken
into account.
Probably all of those captured had already made some growth after
hatching. By early November or the last week of October, racers have
almost or quite completed their season of activity, and are at the
hilltop ledges, preparing to hibernate, if they have not already
retired into dormancy. For 25 young of the year captured in this
period at the end of the growing season, measurements and weights were
as follows: snout-to-vent, 327 (273 to 418) millimeters; tail 93 (72
to 114) millimeters; weight, 12.3 (7 to 19) grams. In the ten-week
period between hatching and hibernation these young had already passed
through their period of most rapid growth, having added, on the
average, more than 50 per cent to their original lengths, and almost
tripled in weight. In these young about to enter their first
hibernation, variation in size and weight is much greater than in the
hatchlings; some have fared much better than others, and there are
significant age differences. Within any one year the time of hatching
is spread over several weeks because of differences in the time of
laying, and differences in nest sites, with variation in heat
received, which promotes or delays the rate of incubation. Year to
year differences in the trend of weather increase the dispersion as
the incubation time is shortened in hot, dry summers and lengthened in
those that are relatively cool and moist.