formerly the upper part of a connecting strip between hilltop and valley
pastures and was altered by the effect of concentrated trampling and
browsing by livestock. It is V-shaped, with the apex at the north end,
and the slope exposures southwest and southeast. The area is bisected
from north to south by a small gully, and remains of an old rock wall.
To the east of this gully the lower outcrop is prominent but west of the
gully, it is but little developed. As compared with other wooded areas,
this one was relatively dry. Trees, and other vegetation in general, are
somewhat more xeric in aspect than are those in Skink Woods. Along the
upper ledge are elms and hackberries, with many thick clumps of fragrant
sumac. The trees are mainly elm, walnut, honey locust, and osage orange
with hardly any oaks or hickories and, with shrubby undergrowth of
dogwood, gooseberry, and coralberry sparser than in adjacent woodlands.
Herbaceous vegetation consists largely of muhly grass, geum, and avens.
On the hilltop edge above the ledge are many flat rocks of varying
sizes, and the slope is thickly strewn with rocks, some of the larger
ones deeply embedded in the soil. The population of five-lined skinks
was relatively sparser than in Skink Woods. Other reptiles including the
Sonoran skink, racerunner, glass-snake, worm snake, ring-necked snake,
blue-racer, bull snake, pilot blacksnake, garter snake, scarlet king
snake, slender tantilla, and copperhead, were more numerous in this area
than in most other parts of the Reservation. The comparatively scarce
prairie skink was found only in this area, and the scarlet king snake
and slender tantilla were found only here and at the quarry.
The Annual Cycle of Reproduction and Growth
SEASONAL OCCURRENCE
Collectors and other observers have often noted that reptiles, in
general, are not found in equal abundance throughout the entire season
of their activity. Many kinds are most in evidence within a period of
weeks after emergence from hibernation, which corresponds with the time
of breeding and later they become much scarcer. In skinks of the genus
_Eumeces_ this tendency is perhaps even more pronounced than in most
other kinds of reptiles. By midsummer or considerably earlier their
period of greatest activity is passed, and in some kinds, adults, or
individuals of any size can rarely be found in the latter half of the
growing season, even by a skilled collector familiar with their habitats
and habits. Thus, Taylor (1936:5) in the preface of his revision of
_Eumeces_, describing the difficulties involved in assembling needed
series of the many Mexican species by collecting on summer field trips,
wrote: "In 1934 in western Mexico ... I met with most disheartening
results ... (although more than 1500 specimens were collected) only a
single specimen of _Eumeces_ was taken. Hobart Smith, in 1934,
accompanied by David Dunkle, made a journey into northwestern Mexico ...
and while generally successful, likewise obtained only a single specimen
of _Eumeces_."
[Illustration: FIG. 7. Seasonal occurrence of five-lined skinks,
based on data collected in 1949, 1950, 1951, and 1952; adult males
and adult females are taken in greatest numbers in May, and in
progressively smaller numbers through the summer and autumn;
yearlings are found in increasing numbers through March, April, May,
and June, then in decreasing numbers through the summer and autumn.]
In the present study the tendency of _E. fasciatus_ to concentrate its
surface activity in early spring was clearly shown. In unseasonably warm
weather in early spring, even in February in one instance, individual
skinks have been found active on the surface or beneath flat rocks
warmed by the sun; but general emergence ordinarily does not occur until
sometime in April, depending on the weather. Unless the weather is much
warmer than the seasonal norm, the skinks spend much of April in a
torpid condition, either not becoming fully active until late in the
month, or lapsing into torpidity with the return of cool weather after
their first emergence from hibernation. During warm periods in April,
however, activity is at or near its annual maximum for all individuals
regardless of sex or age.
In May, with the advent of much warmer weather, daytime temperatures are
usually high enough for the skinks to be active. Adult males travel
about more actively and persistently than females or young, and as a
result they are found so much more frequently that the numbers taken
approximate those for adult females and young combined. Many of the
adult males recorded in May were taken in funnel traps or pitfalls.
Active males in the open were difficult to catch, and a high percentage
of them escaped. To the casual collector or observer, these skinks are
much more in evidence in May than at any other time of year, and most of
those seen are adult males. By June, the numbers of skinks seen in the
open decline abruptly. The adult males become relatively scarce, with
reduction from more than half to about one-sixth of the total, and the
young, about half-grown at that season, make up approximately half of
the total. The adult females make up approximately one-third of the
total June sample, but few of them were found active on the ground
surface. Most were found in nest burrows beneath flat rocks. Under such
conditions they tended to be sluggish in behavior, and were caught much
more easily than were males and young. July was characterized by
progressive decrease in the numbers of adult males, adult females, and
second year young, whereby the numbers of each group were little more
than half of those for June; and by appearance of a new crop of
hatchlings which made up about one-third of the month's sample.
Hatchlings first appeared from early July to late July in different
years; few were recorded in July in some years. Females were much less
commonly found in nests in July than in June because many nesting
attempts were terminated before the beginning of July or early in the
month, and probably because those that remained were often more deeply
buried and better concealed. By August the adult males, and the second
year young (by then approaching adult size) were found in still smaller
numbers, but the number of hatchlings and of adult females approximated
those recorded in July. In the females there is evidently some
resumption of activity after the incubation period is terminated. The
females are then hungry and sometimes emaciated, weighing less, on the
average, than the year-old young of shorter snout-vent length. The
numbers of hatchlings are augmented through early August in some years,
as late broods continue to hatch. By early September few skinks except
hatchlings are to be found, and activity continues to wane throughout
the month. In October skinks of any age or sex group are a rarity, even
though temperature is about the optimum for their activity. Little is
known concerning where and how they spend the fall months. Probably they
are not actually dormant, but retreat underground where temperature is
moderate and humidity is high. Individuals kept in captivity at this
season were listless showing but little inclination to feed. The only
five-lined skink taken on the Reservation in November was found in a
funnel trap after a rain at the end of a long drought. It may have been
attracted to the surface by moisture.
The following table shows the dates on which various events of the
annual cycle were observed in each of five different years. Owing, to
the secretive habits of the skinks, these events generally were not
observed until somewhat after their earliest occurrence in any one
season. The lag was greater in some instances than in others.
Table 3. Phenology of the Annual Cycle in Five Different Years.
=====================+=========+=========+=========+=========+=========
| _1949_ | _1950_ | _1951_ | _1952_ | _1953_
---------------------+---------+---------+---------+---------+---------
Earliest emergence | | | | |
from hibernation | Mar. 30 | ....... | Mar. 24 | Mar. 29 | Mar. 20
General emergence | | | | |
from hibernation | ....... | Apr. 7 | Apr. 14 | Apr. 17 | Mar. 27
Breeding coloration | | | | |
appearing in males | ....... | Apr. 15 | Apr. 25 | Apr. 28 | Apr. 16
Peak of breeding | | | | |
season | May 3 | May 12 | May 16 | May 10 | May 7
Females starting | | | | |
nest burrows | May 26 | May 24 | May 19 | May 19 | May 24
Last appearance of | | | | |
gravid females | June 10 | June 17 | June 29 | June 9 | .......
Earliest appearance | | | | |
of eggs | June 10 | June 13 | June 24 | June 22 | June 16
Earliest appearance | | | | |
of hatchlings | July 5 | July 15 | July 23 | July 3 | July 13
Latest hatching | | | | |
date | July 15 | Aug. 8 | Aug. 8 | July 14 | .......
Latest fall record | Oct. 15 | Sept. 19| Sept. 26| Nov. 9 | Oct. 12
---------------------+---------+---------+---------+---------+---------
SEXUAL CYCLES AND BEHAVIOR
Reynolds (1943:370 and 1947:191) studied the histological and gross
seasonal changes in the reproductive organs of the adult male _Eumeces
fasciatus_. There is a well defined annual cycle. "Early seasonal
increase in seminiferous epithelial heights and in diameter of lumina
and tubules reached a maximum in April followed by regression reaching
complete involution by August. Late seasonal revival of activity
results, by November, in size of testicular elements comparable to those
seen in January. Primary spermatocytes predominate in the germinal
epithelium in January, secondary spermatocytes and spermatids in
February, with spermatids and metamorphosing sperm dominating from March
until late June when the germinal material of the current season is
exhausted." Fifty-three adult males were used as a basis for his study.
These were of diverse origins from Arkansas, Florida, Missouri,
Tennessee, and Indiana. Since sexual cycles in such widely ranging
species tend to be synchronized with local phenology, and change
somewhat from one region to another, the seasonal cycle may have been
somewhat obscured by the diverse origins of the material. The Florida
specimens may have been of the species _E. inexpectatus_. Apparently
Reynolds' experimental skinks were kept in captivity for varying lengths
of time before their reproductive organs were examined. The normal cycle
would almost certainly be altered in captivity, especially in skinks
kept at high temperatures during the time that they would normally be
hibernating.
The seasonal change in gross appearance of the testes is not great. In
the breeding season the testes are slightly enlarged and are firm and
engorged, with pinkish or orange tinge. In immature males, and adults
that are not in breeding condition, the testes are smaller, attenuate,
paler colored, and flaccid. Sizes of testes in some males killed in the
breeding season are recorded in Table 4.
Table 4. Sizes of Testes in Spring and Early Summer in Sexually
Mature and Juvenal Males.
==============+===============+===============+===============
| Snout-vent | Sizes of | Age
Date | length in mm. | testes in mm. | class
--------------+---------------+---------------+---------------
May 6, 1951 | 76 | 7.0 x 4.0 | old adult
May 20, 1951 | 77 | 5.0 x 2.8 | old adult
May 20, 1951 | 74 | 6.2 x 3.2 | old adult
May 20, 1951 | 74 | 5.5 x 3.0 | old adult
May 20, 1951 | 66 | 5.0 x 2.8 | young adult
May 20, 1951 | 65 | 4.2 x 3.2 | young adult
May 20, 1951 | 64 | 5.3 x 3.1 | young adult
May 20, 1951 | 45 | 2.5 x 1.0 | juvenile
May 20, 1951 | 40 | 1.5 x .3 | juvenile
June 3, 1951 | 65 | 5.0 x 2.5 | young adult
June 10, 1951 | 67 | 4.0 x 1.8 | young adult
June 25, 1951 | 75 | 4.0 x 2.0 | old adult
June 25, 1951 | 70 | 3.5 x 1.8 | young adult
June 25, 1951 | 51 | 2.0 x .5 | juvenile
--------------+---------------+---------------+---------------
From the time of emergence in spring, males show some tendency to seek
out females, and frequently a pair may be found together under the same
rock, weeks before the onset of the breeding season. There is no
satisfactory evidence that such associations have any permanence. At
the time of emergence from hibernation the males rarely have even a
trace of reddish coloration on their heads, and more than a month
normally elapses before attainment of breeding coloration. Each year
that observations were made activity of the skinks was interrupted by
cold weather in April, so that the lizards were fully active for only
part of the time between their earliest emergence and their attainment
of breeding condition five to eight weeks later. The reddish suffusion
of the breeding season, hardly showing in the first few weeks after
emergence, appears suddenly within a few days in all adult males of the
population. The best indication of the time necessary to attain breeding
condition was provided by an adult male whose hibernation was
interrupted on December 15 by bringing him into a warm room where he was
kept at 80 deg. F. or more in the daytime, and approximately 70 deg. F. at
night. Thirteen days later, on December 28, the male had developed a
noticeable reddish suffusion. On January 3, nineteen days after
hibernation terminated, the suffusion was near its maximum. When an
adult female was placed with the male on this date, he showed sexual
interest but the courtship was not consummated. On January 6, the 22nd
day, the male's colors had reached their maximum, and when the female
was placed with him, pursuit and copulation occurred promptly.
In the spring of 1952, the first skink of the season was found on March
29, still only partly activated, and under a large flat rock. Skinks
were not caught or seen in any numbers until April 17, however, and
general emergence probably occurred only a day or two earlier than this.
On May 10, 1952, breeding activity was estimated to be at its peak. By
May 28, the reddish suffusion was conspicuously faded in several males
taken. By June 10 it was no longer discernible.
In the immature female the oviducts are small and threadlike, and the
ovaries have grapelike clusters of pale whitish eggs, which are minute,
often less than .5 mm. in diameter (Figure 8A). In sexually mature
females ova enlarge rapidly after emergence from hibernation in the
spring. While eggs are still in the ovary, they are approximately
spherical. In late April and early May the developing ova enlarge
rapidly. Approximate average sizes (dimensions in mm.) of developing
ovarian ova in each of 22 mature females on different dates were as
follows: April 17, 1949: 2.6, 2.3, 2.2, 2.2, 1.9, 1.9; April 18, 1949:
2.2, 1.9, 1.8, 1.1, 1.1; April 24, 1949: 4.6, 3.2, 2.5, 2.3; May 6,
1951: 2.5, 2.3; May 20, 1951: 7.0, 6.2; May 25, 1951: 8.0; June 3, 1951:
6.0, 5.5.
The two females containing ovarian eggs on June 3, 1951, were retarded
individuals, taken along with several others that had already ovulated.
Copulation takes place in early May before the ova have grown to their
full size. In the following weeks both the ova and the oviducts enlarge
rapidly. Upon passing into the oviducts, the ova assume an oval shape
and are approximately 9 by 6 mm. before the albumen and shell are added.
Deposition of a clutch of eggs probably extends over only a day or two
at most, as clutches appear abruptly in the nest cavities. On only a few
occasions were the females found in nest cavities with their clutches
partly laid.
[Illustration: FIG. 8. Adult female skinks with ventral body walls
removed to show reproductive organs. A. Condition in April shortly
before the breeding season; the ovary (O) is still small and
elongate, with the small ova forming a grapelike cluster; right
ovary removed to expose the small bandlike oviduct (OD) beneath it.
B. Condition in late May shortly before ovulation; the greatly
enlarged ovaries are removed to expose the oviducts (OD) now
enlarged and convoluted for reception of the ova. C. Same stage
as B, with mature ova (O) filling most of the body cavity and
concealing other internal organs, I--intestine; L--liver;
approximately natural size.]
Sexual behavior is for the most part limited to a short period of weeks
in spring. In an average year in the area of the study the first two
weeks of May would include the peak and the greater part of the
breeding season. The "courtship," such as it is, and mating have been
described by many observers. However none of the published accounts
seems to include all the essential features in their usual sequence as
observed in the present study. It has been brought out by the studies of
Noble and Bradley (1933:94), Noble and Teale (1930:54) and Schmidt
(1933:71-76) that the sexual behavior of lizards has phylogenetic
significance. Certain basic patterns in mating behavior are
characteristic of saurian families, other traits are characteristic of
genera, while certain details may be characteristic of species, or
perhaps even of subspecies.
In the breeding season the adult male directs the greater part of his
activities to a search for females, and finds them by both sight and
scent. Observations on searching males suggest that they trail females
by scent to some extent, or at least detect their presence in the
general vicinity by this means. Upon discovering a female, the male
pursues her with vigor and determination unless the temperature is too
low, or unless he is not at the height of breeding condition. The female
makes no positive response but reacts to the male's presence by fleeing,
either frantically or perfunctorily, but if she is physiologically ready
to breed the reaction is usually somewhat intermediate between these
extremes. The first reaction of the male as he approaches the female is
to touch her with his tongue, apparently receiving olfactory stimuli
which are essential to the mating pattern. Rushing in pursuit of the
female, he then attempts to seize her in his jaws. Most often a
preliminary grasp is secured on the female's tail. The female may resist
vigorously, wriggling and clawing, turning upon the male to bite or to
threaten with her gaping jaws. At the first opportunity the male deftly
shifts his grip from the female's tail or hindquarters to a more
anterior position, which may be as far forward as the forelimbs or may
be as much as an inch behind them, a little to one side of the
mid-dorsal line. The male secures his hold by pinching loose skin into a
small fold. Having gained this position the male is more or less out of
reach of the female's jaws, and after a brief struggle both rest quietly
except for their rapid breathing, usually for a minute or more, the
ventral surface of the male resting on the female's dorsal surface. The
male suddenly thrusts his tail beneath that of the female. His hind leg
then rests over the base of her tail and the right angle formed by the
laterally projecting hind leg and the tail in each lizard aids to guide
their hindquarters into position so that cloacal contact is established.
Copulation then begins immediately. The male's body may be bent in a
semicircle, to one side of the female, or may be in an S-shaped loop,
depending on whether or not the hemipenis employed is on the side
opposite to that on which the female is grasped. Only one hemipenis is
inserted, but occasionally the other may be everted also. As copulation
begins the male's hind leg, flexed over the female's tail base quivers,
but otherwise there is hardly any movement during approximately the
first one-third of the copulatory period, and this phase may last for
from one to three minutes. Then, abruptly, the male begins rhythmic,
jerky flexions of the proximal portion of the tail, at the rate of
approximately one per second. These tail movements are in a dorsoventral
plane, and there is no perceptible movement of the body. Shortly after
these movements cease, contact is broken usually at the initiative of
the female, as she suddenly struggles to escape and is released either
immediately or after a few seconds by the male. She then moves away,
pressing her cloacal region against the ground. Her movements have
become unhurried, with little or no attempt to avoid the male's
attention. The male usually follows, either close behind, or straddling
the female's tail or body. He may nip at her tail or body repeatedly,
but without securing a grip. When the female pauses, he may come to rest
with his chin or forequarters resting on her. Usually the association
does not last more than a few minutes.
PLATE 1
[Illustration: FIG. 1. Habitat of _Eumeces fasciatus_ near the
center of the "Skink Woods" study area on the University of Kansas
Natural History Reservation, a glade with loose rocks that were
used as nesting sites and shelter by many five-lined skinks.]
[Illustration: FIG. 2. A log on rocky slope in open woods with
sparse undergrowth, fifty feet from center of glade shown in Fig. 1.
The trees are mostly oaks (_Quercus Muehlenbergii_). The decaying
log in middle foreground is much frequented by the skinks as a
shelter and source of insect food.]
PLATE 2
[Illustration: FIG. 1. Old adult male, year-old young and hatchling
in July, showing differences in size and pattern.]
[Illustration: FIG. 2. Adult female skink in a natural nest, with
her clutch of eggs late in incubation. The nest cavity is excavated
in loose soil beneath a flat rock, which was raised momentarily to
expose the nest to view.]
[Illustration: FIG. 3. The same female and nest, with eggs in
process of hatching.]
Noble and Bradley (1933:77) mention frequent homosexual matings between
captive males. However, I observed no homosexual matings, either under
natural conditions or in confinement. The pugnacious behavior of males
that are in breeding condition ordinarily would prevent homosexual
mating. Males in such weakened condition as to be unable to defend
themselves effectively might evoke sexual attack, instead of the usual
fighting response in other males. Although no actual experiments were
performed in the present study in connection with the courtship and
mating behavior, accounts of some workers seem misleading. My own
observations indicate that the capacity for sex discrimination in this
particular kind of lizard, and probably in others, has been underrated.
For example, it has been stated that the male rushes with open mouth at
the neck of any other skink that happens to be around, and he identifies
it as a male if it fights back, or as a female if it does not. On the
contrary my observations indicate that sex recognition occurs almost as
soon as the male is aware of another skink's presence. The red head of
the breeding male is an excellent example of a social releaser in the
sense that this term was used by Tinbergen (1948:8). Like the red belly
of the breeding male stickleback, it facilitates sex recognition and
evokes hostile behavior on the part of other males. Courtship, mating,
and fighting reactions however, seem to be evoked by the interaction of
a complex of social releasers. Whereas males and females are strikingly
different in appearance in the breeding season, visual sex recognition
is complicated by ontogenetic changes. The body stripes characteristic
of the female pattern, become dull or even disappear in some old
females, which then approximate the typical male pattern. On the other
hand newly matured males in their first breeding season retain distinct
body stripes of the female pattern. Their sex is evidenced mainly by
their reddish facial suffusion, which is not quite so extensively
developed as it is in older individuals. Also, in these newly matured
males the temporal region is not so swollen as it is in old males.
The male whose dormancy was terminated in early winter by bringing him
into a warm room causing him to assume breeding coloration and to breed
some four months earlier than those under natural conditions has already
been mentioned. By the time the regular breeding season arrived, this
male had long since undergone sexual regression and retained no trace of
the red suffusion. In this condition, placed in a terrarium with a mixed
group of breeding adults, his social status was of unusual interest. He
exhibited no interest in the females and was less pugnacious toward
other males than were the individuals in breeding condition. Although he
seemed somewhat more nervous and timid, his hostile behavior was not
entirely suppressed, as from time to time he moved up to other males and
bit them viciously. His color pattern resembled those of certain old
adult females in which the body stripes have been suppressed, but the
breeding males evidenced no uncertainty as to his sex and were uniformly
hostile. Their reactions were not noticeably different toward him than
they were toward breeding males. The importance of an olfactory stimulus
as a social releaser in sexual behavior of lizards has not been
appreciated, although Noble and Mason (1933:10) did demonstrate its
importance in the behavior of the female toward her eggs.