state mapped by Braun as the Oak-Hickory Association of the Deciduous
Forest, but extends a little farther west in the northeastern part of
the state. A game type map published by the Oklahoma Game and Fish
Department, Division of Wildlife Restoration, in 1943 shows in more
detail distribution of the main vegetation types within the state. The
locality records for the skink fall almost entirely within three of the
fifteen vegetation types mapped, namely, the oak-pine, and oak-hickory
forest of the state's eastern edge and the post oak-blackjack oak type
of the eastern and central parts. The locality records extend almost
throughout the area occupied by these three types but not in attenuate
westward extensions of the post oak-blackjack type that occur along
several of the main stream courses. In Texas likewise the recorded
localities fall mainly within the area mapped as deciduous forest, but
with several slightly beyond its boundaries. In a detailed map of the
"game regions" of Texas (Anonymous, 1945:1), some of these outlying
localities fall into the coastal prairie area, and the remainder into
the post oak and blackland prairie belts, which grade into each other
and the oak-hickory forest.
The former distribution of the five-lined skink may be postulated on the
basis of the fossil record of its community associates since it is a
primitive and conservative type. Taylor (1936:56) explained the present
discontinuous distribution of the genus on opposite sides of the world
on the basis of a former northern connection of the continents. He
wrote: "I regard migration from North America to Asia as having taken
place via land bridges joining the Alaskan peninsula with Asia either at
Bering Straits or via the Aleutian Island arc to Kamchatka, or both. One
would need postulate but slight climatic changes since the present
climate of this coastal region is probably no more rigorous than that of
southern Canada which has three species of the genus." However, such
former northward distribution, while entirely probable, would have been
possible only in a climate much milder than that which prevails at
present. In Asia, _tunganus_ on the mainland and _latiscutatus_ on the
island of Hokkaido extend north to about latitude 43 deg., and in North
America, _fasciatus_ extends slightly farther north. In order to have
crossed between Alaska and Asia on presumed land bridges these skinks
would have had to extend their ranges about 20 degrees north of their
present limits, into what is now a cool climate. The winter climate of
the Bering Sea is perhaps not much beyond the range of tolerance of the
more cold-adapted forms of _Eumeces_, but the cold, cloudy, wet, and
changeable summer climate is far beyond the range of tolerance of
_Eumeces_ or any other lizard.
It is highly improbable that the fossil record will yield direct
evidence for the existence of a northern ancestral _Eumeces_ of the
_fasciatus_ group. The characters by which the various forms are
recognized are to be found mainly in details of pattern and scalation;
the skeleton is so conservative that specific characters are ill defined
or lacking even in well preserved fossil material. This hypothetical
ancestor probably was a member of a deciduous forest community having
components in common with the modern forests where the American and
Asiatic species occur, along with types now extinct, and others which,
though existing at the present time, have become separated from their
original associates and occur in other regions.
Hollick (1936:11) has described a rich early Tertiary Alaskan flora
strikingly different from that of the same region at the present time.
Composed of genera now characteristic of warm-temperate to subtropical
climates, it was remarkable in having many types of plants that are now
most characteristic of the North American hardwood forests in the
southeastern part of the continent. Besides such widespread genera as
_Fagus_, _Betula_, _Ulmus_, _Platanus_, _Castanea_, _Corylus_,
_Carpinus_, _Crataegus_, _Spiraea_, _Myrica_, _Smilax_, _Pinus_,
_Picea_, and _Abies_, this flora included others now characteristic of
both warm-temperate southeastern North America and Eastern Asia, as
_Magnolia_, _Nyssa_, _Sassafras_, _Persea_, _Benzoin_, _Hamamelis_,
_Liquidambar_, _Celastrus_, _Nelumbo_, and _Onoclea_. It included genera
_Carya_, _Taxodium_ and _Comptonia_ that now are limited to SE North
America, _Sequoia_, now limited to western North America, and also
included several genera which at present are limited to southeastern
Asia: _Ginkgo_, _Glyptostrobus_, _Cinnamomum_, _Hausmannia_,
_Artocarpus_, _Dillenia_ and _Koelreuteria_. This fossil flora provides
strong evidence that in the early Tertiary climatic and habitat
conditions as far north as Alaska were favorable for the existence of an
ancestral _Eumeces_ similar to the modern _E. fasciatus_, which might
have given rise to both North American and Asiatic members of the
_fasciatus_ group.
There is abundant evidence for the existence of an Eocene land
connection between Alaska and northeastern Siberia, permitting free
interchange of faunas between the two continents, as shown by the almost
simultaneous appearance of various mammalian groups in the fossil
records of Asia and North America. Simpson (1947:627) has summarized the
evidence that such intermigrations were occurring throughout most of the
Tertiary, with occasional interruptions as in middle Eocene, and in
middle and late Oligocene, and with increasing selectivity, chiefly a
progressive tendency toward screening out of the groups less tolerant of
cold (judged on the basis of their modern representatives). In the late
Tertiary, and especially in the Pleistocene, animals known to have made
migrations between North America and Asia were types now characteristic
of boreal climates (_e. g._ pika, hare, vole, lemmings, marmot, jumping
mouse, fox, wolverine, bear, moose, caribou, sheep, bison, camels,
mammoth). Simpson believes that there was fairly strong climatic
selectivity even in the Miocene interchanges, and he indicates several
important groups that were non-migrants in the Miocene, most of them
remaining so through the Pliocene and Pleistocene--the primates,
Rhizomyidae, Gliridae, Viverridae, Hyaenidae, Dicerorhininae, Suidae,
late Anthracotheriidae, Hippopotamidae, Tragulidae, Muntiacinae,
Lagomerycidae, Giraffidae, and Bovidae. He states that there is good
evidence that these are all mainly warm-climate animals which are not
likely to have ranged in any force into a cold-temperate or boreal
environment. In view of these conclusions it seems doubtful whether
_Eumeces_ or other reptiles could have crossed the Alaskan-Siberian land
connection so late as the Miocene.
On the contrary, the climate and habitat conditions with which _Eumeces_
might have been associated, although present as far north as Alaska in
the Eocene, evidently had shifted far to the south by mid-Tertiary time.
Axelrod (1950:230) has described a Miocene forest of the Columbia
Plateau and northern Great Basin indicative of a uniform temperate
climate and an average rainfall of thirty-five to sixty inches. This
forest included: (_a_) various genera now characteristic of the
southeastern hardwood forest or confined to it--_Carya_, _Castanea_,
_Comptonia_, _Fagus_, _Liquidambar_, _Nyssa_, _Taxodium_; (_b_) other
genera at present more characteristic of the western United
States--_Sequoia_, _Lithocarpus_, _Pseudotsuga_, _Mahonia_, _Thuja_,
_Gaultheria_, _Amelanchier_; (_c_) wide-ranging genera including
_Alnus_, _Acer_, _Betula_, _Populus_, _Quercus_, _Picea_, _Pinus_,
_Tsuga_, _Cornus_, _Ribes_, _Rosa_, _Hydrangea_; (_d_) modern east Asian
genera, including _Ginkgo_, _Ailanthus_, _Glyptostrobus_, _Keteleria_,
_Koelreuteria_, _Metasequoia_, _Pseudolarix_, _Pterocarya_, _Zelkova_,
which were eliminated from the North American flora in the latter part
of the Tertiary. In short, this western Miocene forest was remarkably
similar in many respects both to the presumably ancestral early Tertiary
Alaskan forest and the modern southeastern hardwood forest. The extent
of this Miocene forest is unknown but judging from the sites where it
has been recorded, it had progressed about halfway, both in latitude and
in actual distance, from Alaska to the area occupied by the modern
southeastern deciduous forests. Several other reptilian genera have
distributions similar to that of the _fasciatus_ group, with
representatives in southeastern Asia and southeastern North America that
probably have parallel histories of distributional divergence from early
Tertiary northern ancestors similar to contemporary species (Schmidt,
1946:148-150). _Alligator_, _Natrix_, _Ancistrodon_, _Scincella_,
_Elaphe_, _Opheodrys_, and within the genus _Eumeces_, the _obsoletus_
group, all provide excellent examples.
EFFECT OF CLIMATIC FACTORS
Accounts of the habits and habitat, by various authors, indicate
versatility in behavior, and adaptation to a variety of habitat
conditions in different climates and plant associations. Some of the
differences evidently result from the skink's tendency to maintain
itself in surroundings of favorable temperature and humidity, which
obviously are to be found in different types of situations at different
extremes of the range. Hence even though the skink itself may remain
unchanged, it tends to behave somewhat differently under diverse
environmental conditions. Such environmentally enforced differences in
habits would be difficult to distinguish from those having a genetic
basis. Although no subspecies of _Eumeces fasciatus_ have been
recognized, local populations undoubtedly differ somewhat in size and
other characters that have a genetic basis.
At the northern edge of its geographic range, _fasciatus_ occurs in
isolated colonies and seems to be restricted to open, rocky situations
which receive the maximum amount of sunlight. Breckenridge (1944:96)
wrote that at the two Minnesota localities representing the northwestern
corner of the known range, the skinks were found at granite outcrops,
and he mentions one found in western Wisconsin, at Taylor Falls, under
an 18-inch slab of a basalt outcrop in sparse oak woods. Patch (1934:51)
described a habitat at Arden, Ontario, among massive granite-gneiss
domes, with sparse vegetation. At Point Pelee, Ontario, the species is
common in the drier, more sparsely wooded situations, hiding beneath
loose bark of stumps and logs.
Ruthven (1911:264) found _E. fasciatus_ in the vicinity of sandy beaches
in the Saginaw Bay region of Michigan. Elsewhere in its range it is more
characteristically an inhabitant of hardwood forests, preferring the
better drained and more rocky situations, according to the testimony of
numerous authors. In eastern Illinois, Smith (1947:33) found it confined
to the area south of the Shelbyville moraine, and not ranging into a
prairie habitat. Near Elkville, Illinois, Cagle found the species
abundant in higher and drier areas within sparse stands of oak in second
growth woods, but it was absent from the low swampy areas adjacent to
streams. Conant (1951:30, 210), describing the habitat in Ohio, stated
that the species does not occur in swamps and areas that are subject to
spring floods nor on dry hillsides, but is abundant in some areas where
there are rotting stumps and logs remaining from former patches of swamp
forest, and usually is found in low, moist situations, in wooded valleys
or even at the edges of swamps and bogs. Lynn (1936:49) wrote that in
Virginia, it is most often seen on steep, boulder-strewn hillsides and
old sawdust piles. In the central Ozarks of Missouri, Owen (1949:49)
found it abundant and saw it almost daily on rocky ledges, fallen
timber, and fence rails, while _E. laticeps_ was seen only once. Taylor
(1936:59) wrote that _E. fasciatus_ occurs where there is timber and is
often found about fallen trees and rotting stumps, or about old
sawmills where wood refuse has accumulated. Smith (1950:187) wrote that
in Kansas the species is commonly found in wooded areas in moist
situations about stones, leaves and rotten logs. Gloyd (1928:120) wrote
that in Franklin County, Kansas, _E. fasciatus_ occurred in upland
situations and was the most abundant lizard where there were rocks,
brush, or decaying wood. Gloyd (1932:401) also recorded it as abundant
in the Pigeon Lake area, Miami County, Kansas, in wooded areas of
sufficient elevation to be out of the river flood-plain.
HABITAT IN NORTHEASTERN KANSAS
In northeastern Kansas I have collected or observed this skink in
several dozen localities, and searched unsuccessfully in numerous other
localities. Absence of this skink, in some situations and its presence
and relative abundance in others, provided a basis for appraising the
environmental factors that are of critical importance. River valleys, of
the Kaw and Wakarusa and their tributaries, with deep alluvial soil,
alternate with flat or rolling upland some two hundred feet higher in
elevation, and having shallow, rocky soil. Where the uplands slope to
the valley floors, there are steep hillsides, usually with extensive
limestone outcrops along their upper slopes. The alluvial plains
formerly supported hardwood forests, while the hill slopes and uplands
were largely prairie. At the present time the bottomland forest has been
almost completely destroyed, as it grew on the most fertile and
potentially productive soil, and has been replaced by cultivated crops.
There are still trees along streambanks, and in occasional woodlots, but
I have failed to find any skinks in such situations. I doubt that they
ever have been numerous in the bottomland woods; lack of rocks for
shelter, and periodic flooding are unfavorable factors. In the Kaw flood
of June and July, 1951, for instance, the entire valley was inundated,
and in smaller tributary valleys such as that of the Wakarusa, flooding
is frequent at the season when skinks are incubating their eggs. The
uplands, formerly prairie, now are used partly for cultivated crops and
partly for pasture. The soil is poor and rocky, and now heavily eroded.
The pastures mostly have a weedy type of vegetation indicative of
overgrazing. Five-lined skinks are absent from most of this upland.
The steep slopes from the upland to the valley floor are now mostly
wooded, and the population of skinks is chiefly in this band of
woodland. Some of the hillsides that have relatively gentle slopes are
treeless and are used for pasture, or are even under cultivation. Where
second growth forest is present its aspect differs depending upon slope,
exposure, and past treatment. Osage orange and honey locust are
aggressive invaders on some dry hillside pastures, and in this type of
woods the skinks are scarce or absent. Some hillside areas, especially
on moist north slopes have thick second-growth woods, in which elm is
usually the principal tree, with several oaks and hickories, walnut,
hackberry, coffee tree, locust and osage orange, and with a dense
understory vegetation of dogwood, gooseberry and coralberry, with vine
tangles of grape, poison oak, and greenbrier. Such woodlands provide
little food for livestock, and are often fenced off from adjacent
pastures. The shading creates conditions unfavorable for skinks and they
are relatively scarce in the denser woods. They are much more numerous
in woodlands that are fenced in with pastures heavily grazed by cattle
or horses, with understory vegetation kept cropped back, and with more
open ground and patches of sunlight. However, they are absent or scarce
in woods that have been subjected over periods of years to browsing, by
sheep or goats, so heavily that hardly any herbaceous vegetation remains
and so heavily that the soil is packed from trampling. Along the upper
slopes, especially about heads of gullies, in areas strewn with flat
rocks, in fairly open mixed woods, with some decaying wood on the
ground, habitat conditions are most nearly optimum for the skinks.
Artificial habitat features, such as rock piles, stone walls, wood
piles, rail fences, or old deserted buildings and sheds, with loose
boards lying about on the ground may support unusually high
concentrations of skinks when the surrounding habitat is favorable.
STUDY AREAS
The University of Kansas Natural History Reservation where most of the
field work for this study was done, has been described in a recent
publication (Fitch 1952:8). While records were obtained from scattered
points throughout the 590-acre Reservation and elsewhere in northeastern
Kansas, field study of this skink was concentrated on four relatively
small areas totalling only about ten acres in extent (Figure 26). These
areas were selected on the basis of abundance and availability of the
skinks, and of variety of habitat conditions represented.
One of these sites was a deserted quarry on a southward projecting spur
of the plateau-like cuesta top, where the upper layers of the Oread
limestone are prominently exposed. In the course of operations, begun
about 1937, the area was denuded of trees and shrubs, and the upper
layers of limestone were removed from a strip about 50 feet wide and
more than 100 yards long. The exposed outcrop presented a vertical rock
face five to ten feet high, with south and southeast exposure. Numerous
jagged seams and fissures in the rock hastened its disintegration.
Quarrying had been discontinued several years before the present study
was begun in 1948. At that time there were talus-like accumulations of
rock and soil several feet wide along the base of the rock face,
supporting a luxuriant pioneer vegetation especially, sweet clover,
stickleaf, ragweed and elm seedlings.
The habitat conditions provided by the exposed rock outcrop at the
border of woods and open land, proved unusually favorable for reptiles
in general, and it was one of the most productive sites on the
Reservation for Sonoran skinks, collared lizards, racerunners,
ring-necked snakes, blue-racers, bull snakes, pilot blacksnakes, scarlet
king snakes, slender tantillas, copperheads, and timber rattlesnakes.
For the five-lined skink, however, this disturbed area was marginal, and
supported only a sparse population. Several decaying two-inch boards
were preferred hiding places where the skinks were found most
frequently, and remains of collapsed rock walls, one in the center of
the area and one at the edge of the woods, were also occupied. Skinks
may have tended to wander away to more favorable situations or may have
been more subject to predation than those elsewhere, since the incidence
of recaptures was relatively low. Most of the records from this general
area were from a ledge in adjacent woods rather than from the quarry
itself. Another site was a rock fill in a ravine below a pond made in
1937. This rock fill was 70 feet long, up to 30 feet wide, and three
feet deep. East and north of the rock pile was a grassy dike, and beyond
it the pond. On the west open grassland extended approximately 200 feet
to the edge of the woods, with a diversion ditch at its border. On the
south end, the rock pile was adjacent to woodland at the base of a steep
slope with north exposure. On this slope the dense stand of second
growth oak and hickory with an almost continuous leaf canopy was a poor
habitat. The rock pile was thus partly isolated and surrounded by areas
that were either uninhabitable to the skinks or supported only sparse
populations of them. By 1948 the rock pile was partly covered by grape
vines. Dead leaves and other debris had accumulated in the deeper
interstices between the rocks. Spiders, beetles, snails and other small
animals were extremely numerous in the vicinity of the rock pile and
provided an abundant food supply. A large sycamore on the west side of
the rocks provided some afternoon shade. This rock pile provided shelter
for reptiles other than the five-lined skink--especially the garter
snake, water snake, copperhead, and brown skink. Another area of about
two and a fourth acres ("Skink Woods," Figure 21) was the one most
productive of skinks. It is a wooded upper slope adjacent to a hilltop
pasture. Along the hilltop rim the upper stratum of the Oread limestone
presents a rock face as much as four feet high at the north end, but
less exposed at the south end where it was partly covered by deposited
soil. Approximately 100 feet down the slope a second outcropping is
present, with many loose rocks and boulders throughout the whole area.
Soil is light and loamy. The slope has a west exposure. The stand of
trees is fairly open, with several large elms, walnuts, and yellow oaks,
and occasional hackberries, ailanthus and red haws. This area was
included in a narrow strip of woodland fenced about 1940 as a runway
connecting a hilltop pasture with a valley pasture where water was
available at a time when both pastures were heavily grazed by horses and
cattle. As a result of trampling, browsing and grazing by livestock,
understory vegetation of this area presented a different aspect from
that in most other parts of the woodland. Saplings of the dominant tree
species and shrubs, notably dogwood, gooseberry and crabapple, were
relatively scarce. Herbaceous vegetation, especially muhly grass, was
conspicuous. By 1953 in the fifth growing season after livestock were
removed, the area still contrasted with other parts of the woodland in
sparseness of shrubby vegetation. Old stock trails were still
discernible, and some sheet erosion and gullying had occurred. The
effect of livestock in holding back woody undergrowth seemed to be an
important factor in improving the habitat as the skinks were much
scarcer in adjacent woodlands on either side that were similar in
species composition, size, and numbers of the larger trees, but
different in having much thicker underbrush. These adjacent woodlands
were not entirely comparable, however, because they had more
north-facing exposures. Reptile associates in the Skink Woods area
include the brown skink, Sonoran skink, glass-snake, worm snake,
ring-necked snake, blue-racer, garter snake, pilot blacksnake,
copperhead and timber rattlesnake, but only the worm snake and
ring-necked snake were abundant.