utilization of choice nesting sites, where such sites are in short
supply in an environment otherwise favorable. Also, the gregarious
tendencies make possible more continuous guarding of the eggs against
such natural enemies as can be repulsed by the female, since each female
occasionally interrupts her brooding to bask or forage.
Many of the nests that I found were in close proximity to others. Often
two nests, and sometimes even three, were found beneath the same rock,
and sometimes a distance of only two or three inches intervened between
the separate clutches. It seemed, however, that in almost every instance
each female had excavated a separate nest chamber originally. In some
instances adjacent nest chambers communicated with each other.
On July 13, 1948, a communal nest was discovered beneath loose bark of a
decaying elm log. There were 22 eggs in the combined clutch, and there
were two females in the vicinity. The bark was raised on several
different days to examine the eggs, and one or both females always were
found with the eggs.
On June 10, 1949, at the pond rock pile, a flat rock was turned and an
unusual nesting aggregation consisting of a minimum of eight females,
and probably more than ten, was found. The nests were somewhat disturbed
by movement of the rock. The ground beneath was honeycombed with tunnels
connecting the flask-shaped nest cavities, which were in part open to
the rock surface on their upper sides. Clutches of eggs numbered 13, 12,
11, 8, and 6 (the last attended by a female which appeared to be still
distended with several more unlaid eggs). Of five other females taken,
two had laid and three were still gravid. Of the five clutches, two had
eggs noticeably larger than those in the other three, and with their
shells mottled brown from adhering earth. These nest cavities were about
half an inch deep and two to three inches wide. The females were
released as soon as they had been examined. One female moved about over
the nest areas exposed, and evinced interest in a lone egg which had
become separated from the others. She moved up to it, standing high off
the ground, with her head turned at right angles to her body as if
preparing to push the egg forward in the angle thus formed, and tested
it with her tongue, but then she became alarmed and left the vicinity.
The flat rock was lowered over the nests again with a minimum of
disturbance.
On July 9, 1949, the flat rock covering the nests was raised again. Most
of the eggs had hatched. Two broods of hatchlings were still in their
respective nest cavities, and one entire clutch had not begun to hatch
although its incubation was nearly completed. Three eggs of _Scincella
laterale_ were found mixed with the _Eumeces_ eggs. One of these was
opened to verify their identity; the other two hatched a few days later
in the laboratory.
The following selected excerpts from my field notes, setting forth
histories of several nests, so far as they were known, give some idea of
the types of nesting sites chosen, the behavior of the females, and the
hazards to which the eggs are exposed.
No. 1. At corner of pond rock pile.
June 21, 1951. Female escaped when rock was turned. One egg measured
12.5 x 8 mm., mud-stained.
June 22, 1951. Nest not in evidence when rock was turned; digging into loose
soil beneath to a depth of about an inch I exposed the eggs but did not disturb
them further.
July 23, 1951. When rock was turned, female did not attempt to escape, but
withdrew to far corner of nest cavity; when caught she voided a large scat
which seemed to consist mainly of _Ceuthophilus_ remains. Largest eggs in
the clutch were 18 x 10 mm. but two were noticeably smaller, and all were
heavily coated with dried mud.
July 30, 1951. Six young in the nest cavity, still not fully active; all of them
were heavily coated with dried mud.
No. 2. At hilltop ledge, under flat rock 13 x 10 x 1 inches, with
one edge sunken in soil; exposed to sunshine for most of day.
June 24, 1951. Female, snout-vent length 70 mm., tail 27-51, weight 5 gms.
Nine eggs, one of which measured 14 x 8 mm.
July 18, 1951. Nine eggs still in their original nest cavity, attended by the
female; she escaped into crevice behind the rock. The eggs were in slightly
damp soil, and in contact with the undersurface of the rock on their upper
sides; one egg was 17 x 10 mm.
July 26, 1951. Eggs caked with dried mud; still attended by female.
July 30, 1951. Dry and empty eggshells in nest cavity, evidently all the eggs
had hatched; no other trace of female nor of young; July 28th seems most
probable hatching date--if, on the 27th, some of eggs almost certainly
would have shown signs of hatching on the 26th when they were examined,
and if on the 29th some stragglers almost surely would have remained at
the nest on July 30.
No. 3. In small gully, on lower slope in hickory woods, beneath rock
9 x 9 x 1 inches, shaded by trees on south side for much of the day,
especially during latter part of morning.
June 24, 1951. The gravid female was deep in nest burrow.
June 29, 1951. When rock was lifted no trace of nest was visible except
for slightly disturbed loose soil at the point where it had been. When
some of this loose soil was cleared away, nest was revealed, with
11 eggs, mud-stained, approximately 12.5 x 8 mm. The female was cold
and sluggish, and did not attempt to escape, but cowered in the back
of the nest burrow, with jaws gaping; she was caught and marked.
July 20, 1951. Eight eggs remaining in the nest--two were accidentally
destroyed in moving them. These two were fertile and contained live
embryos, one of which measured 29 mm. in over-all length. One of the
remaining eggs was 16.5 x 10 mm. Female was present with the eggs.
July 25, 1951. Eggs still present in the nest cavity; female not in
evidence, but might have been concealed in corner of nest chamber as
it was not disturbed.
July 28, 1951. Female was again found with the eggs. One or more of the
seven remaining eggs were punctured in moving them during their
examination. Eggs about 16 x 10 mm.
August 3, 1951. Female was in nest with the eggs some of which are
slightly indented from drying.
August 6, 1951. When rock was turned, female darted out and ran to cover
about ten feet away. The eggs had hatched but two young remained in
the nest cavity, still rather slow and feeble in their movements and
not yet fully active. When routed from cover a second time, the female
ran back to the nest rock and took shelter beneath it.
No. 4. On upper slope above ledge, under a rock 18 x 9 inches, in
site shaded most of day; burrow nearly concealed beneath rock.
June 24, 1951. Nest occupied by a gravid female, apparently ready to lay.
June 30, 1951. Rock covering this nest has been undermined by a mole
tunnel, and many nearby rocks are undermined also. The eggs were
almost certainly destroyed by the mole's tunneling and may have been
eaten by it, since no remains are in evidence.
No. 5. At hilltop ledge beside old abandoned road, beneath flat
rock nine inches in diameter and about 1-1/2 inches thick, shaded
for first half of morning and most of afternoon, but exposed to
mid-day sunshine.
June 29, 1951. Standing water in bottom of nest chamber 1-1/2 inches
below underside of the rock. Some of the eggs are more than half
submerged. One egg is 14 x 8 mm.
July 21, 1951. Entrance of abandoned nest burrow has been enlarged by
running water channelled through in run-off during and after heavy
rains; shrivelled remains of eggs present at the bottom of the burrow.
No. 6. On grassy hilltop a few yards from ledge under flat rock,
9 x 6 x 2 inches.
July 23, 1951. Large female (snout-vent length 75 mm.) with three eggs,
16 x 22 mm.
July 27, 1951. Female escaped from nest cavity as rock was raised. Three
eggs were still in the nest, and a young skink was partly emerged from
one. A second egg not yet hatching was somewhat flaccid, 16 mm. long,
heavily coated with dried mud. The third egg much shrivelled, was opened
and found to have a dead fetus, perhaps a week short of hatching.
July 28, 1951. The flat rock which formerly covered the nest cavity was
found to have been raised and displaced, and no trace of the female,
eggs or young remained. Of possible predators that might have moved
the rock and destroyed the nest, skunk and opossum seemed the most
likely, but there was no definite clue as to the predator's identity.
No. 7. Two feet northeast of pond rock pile, under rock about one
foot square on upper surface with maximum thickness of about eight
inches, lying with upper side at 45-degree angle. The nest was under
one edge, with approximately three inches of rock over it. The rock
was exposed to sunshine throughout the day, except for grass shading
its edges.
July 23, 1951. When rock was turned, the female darted out of the nest
cavity, but in her dash to escape she dropped into a nearby pitfall.
When handled, she voided feces which contained the nearly intact shell
of a skink egg. Six eggs present in the nest; one selected as typical
was 11-1/2 x 8 mm. The eggs were slightly misshapen and might have been
damaged from drying.
July 26, 1951. When rock was raised, female darted out and escaped. The
six eggs still remained in the nest.
August 2, 1951. When rock was raised the female was not in evidence, and
only three eggs could be found; they had fallen from the nest cavity
to the bottom of the depression where the rock was imbedded and were
somewhat dried and indented.
No. 8. North slope, beneath rock approximately 18 x 15 x 4 inches,
at edge of small gully, where shaded most of the time including
mid-day hours.
July 20, 1951. Female attempted to escape from the nest. Four eggs
visible in nest, one 15-1/2 x 10 mm.
July 25, 1951. When rock was raised the female ran from the nest.
July 27, 1951. When rock was raised the female was in the nest with the
eggs; she ran and hid beneath a boulder five feet away. After a few
minutes she emerged and ran 15 feet to a hickory sapling and climbed
it.
July 28, 1951. Female was not in the nest but the four eggs were still
present.
July 30, 1951. Female found dead and partly eaten by ants beside rock
one foot from nest; eggs still present in the nest.
July 31, 1951. Eggs still present in the nest.
August 3, 1951. Eggs still present, including some deep in the nest
cavity which apparently were overlooked previously.
August 6, 1951. One much indented egg found outside the nest cavity was
opened and found to contain a live fetus, seemingly fully developed
and normal. The opened egg was placed on damp soil in a shady place
near the nest, but two hours later the hatchling had been killed and
partly eaten by swarms of ants.
August 9, 1951. The remaining eggs had disappeared, evidently taken by
a predator as no empty shells remained to indicate that the young
had hatched.
HATCHLINGS
Cagle (1940:229 and 232) has graphically described and illustrated the
hatching of the five-lined skink, and numerous observations in the
present study have served to corroborate his description. The first
indication that the time of hatching is at hand is a twitching or
jerking movement within the egg which continues until the shell is slit.
According to Noble and Mason (1933:5) the shell is slit with the
elongate premaxillary egg tooth which has its distal third bent forward
nearly at right angles to its base. Some young remain for an hour or
more with only the snout visible, however, once the head is extruded it
is not again withdrawn unless the lizard is badly startled. The eyes are
opened and blinked slowly, closed for a few minutes, and opened again.
After the eyes have become adjusted, the fore-body emerges and the front
legs are freed. In one clutch, observed by Cagle, hatching time for
individual eggs varied from 45 minutes to five and three-fourths hours.
If startled by visual or tactile stimuli, the little skink may lunge
forward through the slit shell, with a sudden straightening of its body,
and rush away for several inches. Its movements are slow, stiff and
clumsy as compared with those of a skink that is a few days old and
fully active. Hatching of a clutch ordinarily extends over 24 hours or
more. Some of the young may be fully hatched and active before others
from the same clutch have slit their eggshells.
Eggs ready to hatch ordinarily weigh somewhat more than one gram, up to
at least as much as 1.7 grams, but much of this weight is made up of
water absorbed during incubation. The hatchlings usually weigh from .2
to .45 grams. For each of two eggshells recently vacated, that were
washed and squeezed dry, weights were approximately .125 grams.
Hatchlings of the same brood differ perceptibly in size with several per
cent variation in total length, and weight. Some seem to be less fully
developed than others. On July 8, 1952, hatching of the last young in a
clutch was observed. Upon emergence, it differed in appearance from the
others of the brood hatched a few hours earlier. The top of its head
bulged slightly as in fetuses. The umbilicus was not yet closed, and the
protruding yolk mass hindered the hatchling's movements and made
crawling difficult. In order to progress it had to stand high off the
ground to prevent its ventral surface from dragging. Protrusion of the
yolk mass has been described in newly emerged hatchlings for the closely
related _E. anthracinus_ (Clausen, 1938:3-7) as well as in _fasciatus_.
Cagle (_loc. cit._) states that the mass of yolk is at first about 3 mm.
in diameter, but is completely used at the end of the third day. A group
of young retained by him, without food, died the sixth day after
hatching, seemingly from starvation. Three of five recently hatched
young were found by Cagle to have eaten ant pupae placed in a box with
them on the preceding day, even though the skinks still retained the
yolk masses. One hatchling of this group ate its own tail that had been
broken off in handling. Cagle described a color change taking place
during the first few hours after hatching; the ground color, dull
greenish at first, darkens to an iridescent black, the pale stripes are
altered from an original tan color to bronze, with a tinge of reddish on
the head, and the ventral surface which is partially transparent showing
the outlines of the internal organs at first, soon becomes opaque white.
Contrary to the statement by Noble and Mason (1933:5) that in captivity
the hatchlings seldom stayed together more than a few hours, litters of
young fully active, a day or two after hatching were found in the nests
with the females still looped around them on several occasions. On one
such occasion, although the brood scattered immediately into surrounding
vegetation where they hid, I succeeded in catching the female and six of
the young, and put them all together in a nylon bag to carry them back
to the laboratory. Several hours after the bag had been placed on a
table it was noticed that the family had again gathered into a compact
cluster in the bag with the female's body looped around the young in the
characteristic brooding position seen in those with young or eggs in
their nest cavities. When hatching is complete, the female may leave
before the young have dispersed. On August 5, 1950, a nest under
observation was found to have all of the young or most of them still
clustered in the cavity, but the female was not in evidence. The young
were active, and immediately took alarm as the rock was raised exposing
them. Almost instantly, they scattered and vanished. Subsequent search
revealed five of the young, each poorly concealed in tufts of grass or
under dry leaves or other ground litter at the edges of the depression
where the rock had lain. Once hidden, these young were reluctant to run
again and depended on concealment.
Having once left the nest, the young probably do not return to it, as
many nests examined within a few days after hatching were never found
occupied either by females or young after their original dispersal. As
soon as the dispersal occurs family ties are permanently severed. On
July 19, 1950, a group of active hatchlings was observed moving about
over a log, on what was probably the first day of activity away from the
nest. The log was in the bottom of a steep-walled gully, where it had
come to rest the night before. It had been an erect but dead and partly
undermined snag on the edge of the gully, and was blown down that night
in a violent thunderstorm. Most of the log was held clear of the rushing
water in the bottom of the gully by projecting limbs. The little skinks
were darting in and out of holes and crevices in the log, pausing
frequently to bask. As many as four were in sight simultaneously, but
probably the total included several more, as it was difficult to keep
track of individuals. An adult female, presumably the mother of the
litter was also present, but she took no interest in the young, and they
showed no evidence of dependence on her. On the contrary, several times
when one or another of the young happened to come near the female in the
course of its wandering, and noticed her, it was seen to shy away in
sudden alarm.
[Illustration: FIG. 11. Sizes on specific dates of young hatched in
1950 and 1952. Approximate size ranges at different times of year,
and differences in trend between the two years are brought out.]
The young were much more active than the female. These and other young
observed in the open were almost constantly in motion. Pauses to bask at
any one spot were of only a few seconds duration. A certain log in Skink
Woods evidently was the site of one or more successful skink nests each
year that observations were made, although a nest was actually found in
it only in 1948. On July 26, 1950, recently hatched young were active on
this log. Temperature was about 22 deg.C. and the young were alternating
frequently between shade and sunshine to maintain their body
temperature. Collectively they seemed to cover every square inch of the
log surface, poking and probing into niches, crevices and insect
borings. They had a tendency to seek out the highest points on the log
as resting places.
In moving about, foraging or sunning, the young often carry the tail
arched high, and keep it in motion with slow squirming undulations.
These undulations may be continued even when the lizard itself has come
to rest momentarily. The movements of the tail together with its vivid
blue color serve to attract attention to it. Such behavior has not been
observed in adults or partly grown young. Jopson (1938:90) observed an
instance in which two dogs cornered a young five-lined skink (either the
present species or _E. laticeps_) but were distracted by the wriggling
of its bright blue tail "either dropped by autotomy or knocked off" so
that the skink itself was allowed to escape. On another occasion these
same two dogs attacking an adult male skink, were not distracted by the
wriggling but dull colored broken tail, and they killed the lizard.
GROWTH
The subject of growth in _Eumeces_ was briefly discussed by Taylor
(1936:66) in his revision of the genus. Sorting fairly large series of
museum specimens into seeming age-size groups, Taylor concluded that
skinks require as much as 9 or 10 years to attain adult size. For
_fasciatus_, for instance, the snout-vent length of 65.7 mm. (small
adult size) was considered typical of individuals in their ninth year of
life, with yearly gain of only 6 or 7 mm. in length in the young. I have
seen the original data on which this conclusion was based, and the age
groupings, as assigned by Taylor, seemed plausible. However, in the
light of present knowledge, it is certain that the seeming intervals
between his assumed age groups would have disappeared with a still
larger series of specimens. The eight or nine size groups that Taylor
recognized as distinct annual age groups actually comprise only two age
groups, each having such wide dispersion of individuals (by retardation
of some and acceleration of others) that there is overlapping in size
between them.
Growth in reptiles is now much better understood. Many species have been
studied by a variety of methods, including observation of growth in
captives, recording of growth in marked individuals living under natural
conditions, and sorting of large series into age-size groups. Two
species of _Eumeces_ have been studied in some detail. Breckenridge
(1943:601-602) marked all the individuals of _septentrionalis_ that
could be found in a small colony in Minnesota and he concluded from the
growth recorded in several that were recaptured, that these skinks grow
to mature size (65 mm. and larger) at the end of their second year of
life and are ready to breed the following spring. Rodgers and Memmler
(1943:61) plotted the size distribution of a large year-round collection
of _skiltonianus_ from near Berkeley, California. They found that in
this species hatching occurs in July and August, hatchlings are about 25
mm. in snout-vent length, and grow to about 50 mm. by the time they are
one year old, and to about 65 mm. at two years of age, but most of them
breed at the end of their third year. Within the genus the species
_septentrionalis_ and _skiltonianus_ belong to groups separate from each
other and from that including _fasciatus_. While _septentrionalis_ and
_skiltonianus_ resemble each other in their growth pattern and in the
time required to reach sexual maturity, _fasciatus_ is notably different
in its more rapid growth and the shorter time it requires to reach
breeding maturity. This would scarcely be expected, as all three are of
similar size. Furthermore, _skiltonianus_ in the region of Rodgers' and
Memmler's study has a longer growing season than _fasciatus_ in
northeastern Kansas, while _septentrionalis_ in Minnesota has a growing
season markedly shorter than either. It is noteworthy that each of these
three skinks is the northernmost lizard in the section of the country
where it occurs.
In the present study growth was investigated by measuring and marking
large numbers of young, many of which were recaptured for subsequent
records, and by sorting into age-size groups all available measurements.
An understanding of the latter set of data was facilitated by
correlating it with the growth records of marked individuals. Changes in
the phenology of growth from year to year according to weather
conditions were noted.
As already indicated, hatching occurs from early July to mid-August in
northeastern Kansas. Unseasonably cool weather with frequent rains may
cause cumulative delay in breeding and incubation so that hatching may
average several weeks later than it does in years with relatively warm
and dry weather during the breeding season. Within any one year hatching
time is concentrated, so that the majority of the young hatch within a
period of two weeks, but microclimates in the situations where the nests
are made may differ enough to cause this much spread. Individuals living
on north slopes in thick woods, and receiving the minimum amount of
sunlight may have their emergence from hibernation and attainment of
breeding condition delayed. Later, nesting in the same situations, they
may have incubation of their clutches similarly delayed.
Newly hatched young average just under an inch in snout-vent length
(23-27 mm.) and weigh .2 to .45 grams. Most rapid growth occurs in the
period of weeks following hatching. The growth rate during this late
summer period cannot be well shown by comparing average size of series
taken on successive dates, because each series is likely to include some
newly hatched young.