experience with _fasciatus_ in parts of its range other than
northeastern Kansas, that the phenology of the breeding cycle is subject
to geographic variation, synchronizing with the somewhat different
climatic conditions under which the species occurs. However, the
difference is less than might be expected, in view of the species'
extensive range. As a result of the early spring, and the warm summer
climate in the southern states, dates of laying and hatching may be
several weeks advanced. On April 12, 1952, Dr. Wilfred T. Neill showed
me several live _E. fasciatus_, collected a few days before along the
Trinity River in southeastern Texas, which appeared to be at the height
of breeding condition. In northeastern Kansas on that date, general
emergence had not yet occurred, and it was not until about May 10 that
the population attained the peak of breeding condition. On May 8, 1948,
near Burr Ferry, Vernon Parish, Louisiana, I caught an adult female in
her nest burrow, and she contained eggs ready to be laid. Data with
which Mr. Robert Gordon kindly provided me for specimens from southern
Louisiana and southeastern Texas, in the Tulane University collection,
indicate gravid females on June 4, 1952, and June 17, 1948 (3), and
females with their egg clutches on June 16, 1948, June 17, 1948, June
23, 1950; and hatching dates in captivity of July 19, 1949, July 19,
1950, July 25-26, 1949. These dates correspond well with those for
specimens obtained in northeastern Kansas in the same years. In the
northern part of the range, Ruthven (1911:264) recorded that in the
Saginaw Bay region, females taken on June 19 had eggs nearly ready to be
laid, and after July 2 clutches were found frequently; young of the year
were first observed on July 31. A juvenal specimen in the University of
Minnesota Natural History Museum, collected on August 11, 1938, at
Dresser Junction, Wisconsin, is 30-1/2 mm. in snout-vent
length--approximately the size of juveniles in northeastern Kansas at
the same season. Evans and Roecker (1951:6) record hatching as occurring
in the first week of September at Arden, Ontario, indicating that at the
northern edge of the range hatching may be delayed as much as two
months. With such delayed hatching, but little time remains for the
young to grow before they are forced into retirement for hibernation.
FIGHTING
Territoriality in the usual sense is lacking in the five-lined skink,
and could scarcely exist in an animal of its habits. To defend a
definite area (territory) against intruders of its own species, the
animal would have to detect such intruders promptly. The skink, however,
is so secretive in habits that at any given time the individual is
likely to be hiding and inactive, even when conditions are favorable for
it to be in the open, and other individuals therefore can then wander
onto its home range unopposed. Even when an individual is active, it
lacks the ability to detect others, except within a radius which would
encompass only a small fraction of the entire home range. The senses
are inadequate to inform one lizard of the presence of another until the
two are only a few yards, or even a few inches apart. Usually the lizard
is on the ground, where even small objects obstruct its view, and vision
is probably effective for only a few yards. Hearing is probably
effective for about the same radius in detecting animals of
approximately its own size. Scent is effective in detecting prey near at
hand or on contact, but probably does not serve for detection of other
lizards that are not in the immediate vicinity. Therefore, the area
covered by one in the course of its normal activities may harbor many
others, and individuals most of the time are unaware of the others on
their home ranges.
Under most circumstances these skinks behave toward each other with
tolerance or indifference, but during the breeding season adult males
become hostile, and fight on sight. Their reddish facial suffusion
serves as a social releaser which elicits hostile behavior and
facilitates sex recognition. As the breeding season wanes, the reddish
suffusion fades rapidly and male hostility, probably controlled by the
same hormonal complex, is likewise suppressed. Hostile behavior is rare
in adult females or young at any time.
Combats and pursuits have been observed most frequently the last week of
April and especially in the first two weeks of May. At this season
funnel traps set along rock ledges often caught two adult male skinks
together. In almost every instance one of the two confined males was
mutilated, with pieces of skin and flesh bitten from the tail and with
chin, snout, and neck scarred; most serious wounds were usually in the
sacral region or base of the tail or both. Often the wounds were so
severe that the skink died in a short time in captivity and presumably
others that were released died also.
On April 28, 1949, a large adult male skink, chased by another, ran out
in the middle of a trail and stopped. The pursuer stopped a few inches
from it, then after a long pause, retreated in the direction from which
it had come. For the five minutes that the pursued skink was watched, it
lay motionless, partly hidden by dry leaves, evidently seeking to avoid
further pursuit by concealment. I caught it without difficulty, and it
seemed weak and dazed, as if injured in the fight. Its reddish suffusion
was conspicuous, but not fully developed.
On May 3, 1949, an adult male having bright red facial suffusion was
observed searching persistently in ground litter; he was seen to find
and pursue a female, and to copulate. A few minutes after mating was
completed and the pair separated, a second male also searching in the
vicinity came within sight of the first one. The two noticed each other
at a distance of about 18 inches, indicating their awareness by their
more alert, jerky movements, and spasmodic vibrating of their tails. The
newcomer darted at the other, and for a moment they dodged and sparred.
As one broke away to run, the other seized it by the tail. They were on
an exposed tree root about an inch in diameter. The skink that was
caught twisted its body around underneath the root and seized its
adversary by the tail likewise, so that their linked bodies encircled
the root, each squirming to disengage itself from the other's jaws.
After a few seconds they did break apart, and then maneuvered briefly
menacing each other at close quarters, but they gradually moved away and
lost contact.
On May 10, 1949, two adult males were seen to approach each other
slowly, pausing for perhaps a minute when they were a little more than
one foot apart. Then one edged up to the other, and with a sudden lunge
seized it by the head. The one seized broke away with a vigorous jerk,
and promptly retaliated by biting the first one's head. After a few
seconds of rapid sparring and thrashing, they broke apart, and one
chased the other for several feet until it eluded further pursuit by
dodging and hiding.
[Illustration: FIG. 9. Adult male skinks fighting. A. Menacing
approach. B. One has lunged and secured a grip on the other's side,
holding it at right angle. The one caught is unable to flex its
body and neck enough to secure a retaliatory grip on the attacker,
and must break away by violent thrashing.]
On May 12, 1950, my attention was attracted by a rustling in dry leaves.
Within a few inches of my foot two adult males were struggling fiercely
with jaws interlocked. Sudden violent twisting and thrashing alternated
with quiet periods of a few seconds duration, in which the lizards
scarcely moved except for heavy panting and twitching of their tails.
After perhaps two minutes of fighting, one broke away and ran. For a
distance of several feet it was closely pursued by the other, which,
however, soon lost contact with it in the rough terrain and surface
litter.
On May 12, 1951, rustling in dry leaves attracted my attention to two
large adult males fighting. For about fifteen minutes that they were
observed, they struggled, with neither yielding ground, though they
thrashed and rolled about over an area of several square feet. Sometimes
they were disengaged for short intervals. Then facing in opposite
directions, with their heads side by side, they would snap at each
other's necks and shoulders (Figure 9). Part of the time both males had
grips and were biting each other simultaneously, but more frequently one
or the other had a temporary advantage. When one secured a grip it would
strain to the utmost, biting as hard as it could and lunging forward
with frequent short jerks, meanwhile striving to keep out of reach of
the other's jaws. The one caught in the attacker's grip was usually
unable to flex its body sharply enough to reach its opponent at all, or
could barely reach it at such an oblique angle that its jaws slipped off
the smooth body. Sometimes the one held did succeed in catching the
other's front foot. The one caught in the other's jaws always succeeded
in tearing loose after a short time. In the interval while the attacker
rested with jaws partly relaxed, the victim had an opportunity to break
away. Even when both were free, they did not obtain grips easily, but
often made several unsuccessful lunges and bites, the jaws of each
slipping off the firm, smooth sides of its opponent. Sometimes the
attacker seized a fold of skin, or sometimes obtained a wide grip on its
body. One which had obtained a grip sometimes rolled rapidly, spinning
the other around and dashing it against the ground. As these rotations
stopped, the victim might come to rest on its back in such a position
that it was temporarily helpless, but always broke loose after further
struggles. Neither showed any inclination to retreat until finally, when
they were interlocked, rolling about almost at my feet, I attempted to
catch them. Then they instantly disengaged and rushed away, and one
escaped. The one caught had suffered but little injury in the fight.
Numerous tooth marks were discernible as minute abrasions on the surface
of the scales, but the bony dermal armor had not been perceptibly
penetrated during the prolonged and violent struggle.
EGGS
The eggs of _Eumeces fasciatus_ are like diminutive chicken eggs in
appearance. They are white when first laid, slightly translucent when
held to the light. Within a day or two after they are laid, these eggs
are soiled to a dull tan color, somewhat mottled, as a result of being
rolled and dragged about in contact with the floor and wall of the nest
burrow. Like the eggs of most other reptiles, those of _Eumeces
fasciatus_ have parchmentlike shells. These shells are thin and easily
punctured. As incubation proceeds, the egg enlarges by gradual
absorption of moisture and the somewhat elastic shell is stretched. An
egg left in water for as much as a day does not gain in weight
appreciably. Except for occasional abnormal ones, the eggs of any one
clutch are notably uniform in size and shape at the time they are laid.
As incubation proceeds, some eggs enlarge more rapidly than others, and
attain larger ultimate size. Differences in shape also appear, some eggs
becoming relatively elongate and thin, while others are thick and blunt.
Some become distorted to asymmetrical shapes. In nests that have been
deserted by the females, eggs of irregular shape are especially
noticeable. It seems probable that the frequent shifting of the eggs by
the female prevents unequal drying or stretching in different areas of
the shell. Normal young were observed to hatch from grossly misshapen
eggs. Under conditions of drought, the eggs may not enlarge normally
during the latter part of incubation, and may become indented or partly
collapsed, and yet apparently normal young hatch from them. Both in the
field, and in laboratory experiments, eggs were found to have remarkable
tolerance for excess moisture. After heavy rains of summer
thunderstorms, nests were sometimes found to have water trickling
through them, and on occasion eggs were found to be partly submerged in
water in the nest cavity. Exposed rocks at the heads of small gullies
often were chosen by the female skinks as the shelter for their nests.
In these situations the nests were exposed to run-off water. In July,
1951, especially, unusually heavy precipitation resulted in the flooding
of many nests. In some instances desertion by the females and
destruction of the eggs seemed to have been caused by this flooding,
even in the well-drained hillside situations where this study was made.
Table 5.--Measurements in Millimeters and Weights in Grams of Eggs
in the Same Clutch at Different Stages During Their Incubation,
Showing Gradual Increase in Size.
===============+=========+========+========+========+========+========+========+===========
| June 17 | June | June | June | July | July | July | July 30
| (laid) | 18 | 24 | 28 | 17 | 20 | 28 | (hatched)
---------------+---------+--------+--------+--------+--------+--------+--------+-----------
Average length | | | | | | | |
(for 7) | ..... | .... | .... | .... | 13.7 | 14.3 | 14.7 | .......
Average width | | | | | | | |
(for 7) | ..... | .... | .... | .... | 10.5 | 10.9 | 11.1 | .......
Typical length | ..... | 11.1 | .... | 12.5 | 14.0 | 14.3 | 14.8 | .......
Typical width | ..... | 7.5 | .... | 9.9 | 11.0 | 11.2 | 11.0 | .......
Maximum length | ..... | 11.5 | .... | .... | 14.5 | 15.0 | 15.5 | .......
Maximum width | ..... | 7.5 | .... | .... | 10.9 | 11.1 | 11.4 | .......
Minimum length | ..... | 10.5 | .... | .... | 12.5 | 12.8 | 13.5 | .......
Minimum width | ..... | 7.0 | .... | .... | 9.9 | 10.0 | 10.5 | .......
Average weight | ..... | .38^10 | .58^5 | .63^9 | .82^8 | .90^7 | 1.0^7 | .......
Typical weight | ..... | .4 | .... | .... | .... | .9 | 1.0 | .......
Maximum weight | ..... | .... | .... | .... | .... | 1.0 | 1.1 | .......
Minimum weight | ..... | .... | .... | .... | .... | .7 | .7 | .......
---------------+---------+--------+--------+--------+--------+--------+--------+-----------
Superior number indicates the number of individuals averaged.
The extent of tolerance to immersion in water probably depends on the
stage of development, the temperature, the oxygen content of the water
and other factors. One egg was fully immersed for ten minutes on July
20, 1951, then returned to a container with damp soil in the laboratory,
where it seemed to develop normally. On July 30 it was opened and found
to have a living fetus, which was a week short of hatching. On July 22
another egg of the same clutch was immersed and left in water for 23
hours. On July 30 it was ruptured in handling and found to contain a
living fetus. On July 31 two eggs were placed in a dish of water in a
refrigerator. On August 5 they were removed and opened. Fetuses were
dead and were not appreciably larger than the one of the same clutch in
the egg opened on July 31. On August 5 two of the remaining eggs of this
clutch were placed in a Petri dish, partly immersed in water, with
approximately one-fourth of the surface of each protruding and exposed
to the air. Forty-eight hours later it was found that both eggs had
hatched. Evaporation had reduced the water in the dish to an amount
sufficient to cover only about the lower one-third of each egg. One
hatchling was missing, evidently having climbed out of the shallow dish
and escaped to the floor. The other was found still standing in the
water with its head protruding, and it was lively and in good condition.
The remaining four eggs in this clutch, which had been kept in a
container of damp earth, were also hatching on this date. On July 10,
1952, an egg in a late stage of incubation was immersed in water in the
laboratory. On July 14 when removed, it had fungus growing on it, and
was found to have a dead fetus, nearly full-sized.
The range of temperature tolerance of the embryo is wide, probably
comparable to that of the adult. Time required for incubation is
dependent on temperature. Persistently wet and cloudy weather in the
summer of 1951, keeping temperatures relatively low in nests, was a
contributing cause to late hatching that summer. As compared with 1952,
hatching was about one month delayed in 1951, but later emergence and
breeding accounts for part of the difference. The extent to which low
temperature may delay incubation was indicated by the effect of
refrigeration on several experimental eggs, as recorded below.
1. July 8, 1952 Egg transferred from natural nest to jar of damp soil
in refrigerator at 13.8 deg.C.
July 14, 1952 Seems to be in good condition.
July 19, 1952 Partly collapsed. Weight and measurements same as on
July 8; opened and found to contain a dead fetus.
Snout-vent length 23 mm., forehead bulging, skin
delicate and membranous. Colors somewhat dull,
indicating that it was not quite fully developed,
although it had attained the minimum hatching size.
2. July 10, 1952 Egg from natural nest (15.0 x 10.5 mm., .95 gm.) put
in refrigerator at 11.6 deg.C. Control (14.5 x 10.6 mm.,
.8 gm.) from the same clutch kept in hatching medium
in laboratory.
July 13, 1952 Control egg hatching; refrigerated egg shows no
indication of hatching.
July 14, 1952 Experimental egg 15.8 x 10.8 mm., 1.0 gm., seems to be
in good condition. Nest from which it was taken found to
have all remaining eggs hatching today.
July 19, 1952 Experimental egg 15.0 x 10.0 mm., 1.0 gm., removed from
refrigerator and transferred to container in damp rotten
wood in laboratory. Seems to be in good condition.
July 23, 1952 Experimental egg found to be hatched this morning, and
hatching must have occurred either in the night or late
yesterday. Eggshell still damp and pliable.
3. July 10, 1952 Egg from natural nest (14.0 x 10.5 mm., .8 gm.) put in
refrigerator at 11.2 deg.C., in container with damp decayed
wood. Control egg (14.2 x 10.1 mm., .8 gm.) from the
same clutch kept in the same hatching medium in the
laboratory.
July 12, 1952 Nest from which experimental and control eggs were
taken has started to hatch, and two hatchlings were
seen there.
July 13, 1952 Control egg hatched.
July 14, 1952 Experimental egg 14.2 x 10.1 mm., .8 gm., seems to be in
good condition. Nest in field examined and all eggs were
hatched, with only three of the hatchlings remaining,
the others having dispersed.
July 19, 1952 Experimental egg 14.0 x 10.0 mm., .95 gm., still appears
to be in good condition; removed from refrigerator and
kept in laboratory.
July 23, 1952 Experimental egg found to be hatched, and hatchling
active although still in hiding beneath rotten wood.
Probably it hatched early in the day of July 22; the
empty shell is still moist.
These experiments seem to show that, in the later stages of incubation
at least, lowering of temperature to 11 deg. or 12 deg.C. almost halts
development of the fetus. Harm does not necessarily result, however, and
when again warmed to normal incubation temperatures, the eggs eventually
hatch, the incubation period being lengthened by a time approximately
equivalent to the interval of refrigeration.
Under natural conditions the time required for incubation probably
varies within wide limits, controlled mainly by temperature. No two
clutches receive the same amount of heat, as sites differ greatly in
extent of insulation, and exposure to sunlight. Each year, earliest
appearance of hatchlings is in a warm, sunny situation, and in cooler,
well shaded places hatchlings appear somewhat later. Their incubation is
evidently somewhat protracted, although later emergence from hibernation
and later breeding of adults in these situations might also contribute
to the delay.
Widely different incubation periods have been recorded in the literature
and the variation probably is not due to temperature alone. Noble and
Mason (1933:4) recorded incubation periods for six females from the same
locality, and evidently kept under the same laboratory conditions, as
47, 41, 36, 29, 29, and 27 days. Despite the wide difference in
incubation time, all six clutches hatched within a 12-day period from
July 5-17. It seems improbable that differences in temperature account
for the 20-day disparity between maximum and minimum incubation time, in
these females kept under similar conditions. Cagle (1940:229) recorded
an even shorter incubation period for one kept in the laboratory, which
laid eggs on June 30; hatching occurred on July 23 and 24. Retention of
eggs in the oviduct by females kept under unnatural conditions would
partly explain their late laying and the short incubation period of
their clutches. Such ability to retain eggs in the oviduct while their
development proceeds would not be especially surprising in _E.
fasciatus_ since its congener _E. lynxe_ of the highlands in southern
Mexico is normally ovoviviparous (Hartweg, 1931:61; Taylor, 1936:171).
Cagle did not determine incubation time for any of the natural nests
found, but evidently in all of them laying occurred earlier than in the
single female brought to the laboratory while still gravid. All the eggs
in natural nests found by him were brought to the laboratory and most of
them were hatched. Cagle remarked: "The fact that these 26 nests hatched
within a period of nine days seemingly indicates that the egg laying
period extends over not more than two weeks."
In the present study no incubation periods so short as those recorded by
Noble and Mason, and Cagle, were observed. Incubation times were
recorded for clutches both in the laboratory and in the field, but for
most of the clutches only approximate incubation periods were recorded.
Failure to record the exact date of laying or of hatching, or both
resulted from attempts to avoid frequent disturbance of females in their
nests, which might have caused them to desert.
One clutch of eggs laid in a terrarium probably on June 17,
1951--possibly a day or two earlier--hatched on July 30, after an
incubation of about 44 days. Another clutch, found in a terrarium on
July 17, 1951, was estimated to have been laid about a week earlier,
judging from the average length (11.8 mm.) and average weight (.55 gm.)
of the eggs. These eggs hatched on August 9, a little more than three
weeks after their discovery. A clutch found in the field on June 25,
1951, evidently recently laid (average length 12 mm., weight .45 gm.),
hatched 41 days later, on August 5. Another clutch found in a terrarium
on July 17, 1951, was estimated to have been laid ten days or two weeks
before, as the average length was 12.7 mm. The eggs hatched on August 7,
three weeks after their discovery. On June 25, 1951, an incomplete
clutch of three eggs was found with a female which still had an unlaid
egg. The three eggs probably had been laid the same day or the day
before. They were kept in the laboratory and weighed and measured at
intervals until July 28, 33 days after their discovery when both those
that remained were accidentally punctured and found to have nearly full
term fetuses. In the field a nest which contained only a gravid female
on June 24, 1951, had a clutch of eggs already mud stained and slightly
enlarged on June 29. The most probable date of laying was June 26. On
August 6 the eggs had all hatched but several young were still in the
nest. Probably most hatched on August 5. The incubation time was hence
approximately 40 days.
On June 21, 1951, a natural nest was found with eggs already somewhat
enlarged (12.5 x 8 mm.) and mud stained. This nest was checked from time
to time in the next few weeks, and after 39 days, on July 30, it was
found that all the eggs had recently hatched, but six young were still
in the nest cavity.
Another nest was found on June 24, 1951, with the eggs already markedly
enlarged (14 x 8 mm.) indicating that laying must have been several days
earlier--probably well over a week. Hatching occurred approximately 34
days later, probably on July 28, since on July 26 there was no sign that
hatching was imminent, and on July 30 only the empty dried eggshells
remained in the nest.
The incubation time approximated six weeks for those nests with most
complete records. Under wet and stormy weather conditions such as
prevailed in 1951, this may have been the normal incubation period, but
in warmer and drier years incubation time is shortened.