The American _Eumeces laticeps_ and _E. inexpectatus_ seem t_Life History and Ecology of the Five-Lined Skink, Eumeces fasciatus

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UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY

Volume 8, No. 1, pp. 1-156, 2 pls., 26 figs. in text, 17 tables

September 1, 1954

Life History and Ecology

of the Five-lined Skink, Eumeces fasciatus

HENRY S. FITCH

UNIVERSITY OF KANSAS

LAWRENCE

1954

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard,

Robert W. Wilson

Volume 8, No. 1, pp. 1-156, 2 pls., 26 figs. in text, 17 tables

Published September 1, 1954

UNIVERSITY OF KANSAS

Lawrence, Kansas

PRINTED BY

FERD VOILAND, JR., STATE PRINTER

TOPEKA, KANSAS

1954

25-3559

LIFE HISTORY AND ECOLOGY OF THE FIVE-LINED SKINK, EUMECES FASCIATUS

Henry S. Fitch

Introduction

The common five-lined skink (or common blue-tailed skink) is a small

woodland lizard, abundantly and widely distributed over the eastern

United States. Many authors have casually discussed this lizard or have

treated in detail some phase of its biology. Excellent brief summaries

of the known facts concerning its life history have been published by

Smith (1946:349-350 and 1950:187-188) and Pope (1947:153-157).

Nevertheless, no thoroughgoing study of its life history and ecology has

heretofore been made.

In 1932, taxonomic studies by Dr. Edward H. Taylor revealed that the

lizards previously referred to in the literature as _Eumeces fasciatus_,

actually were three closely related and similar, partly sympatric

species. Although Taylor's work was careful and detailed, and indicated

numerous minor differences by which the three species could be

distinguished, many herpetologists were reluctant to accept his findings

for nearly a decade thereafter. Consequently a large amount of

literature concerning five-lined skinks is either obviously composite in

the sense that it is based upon two or three species, or is not

definitely assignable to any one species. In the study here reported

upon, all pertinent literature available to me has been examined, and

evaluated, and important findings of other authors have been

incorporated in the discussion. However, mine was primarily a field

study, and in one small part of the geographic range of the one species.

The University of Kansas Natural History Reservation is a tract of 590

acres preserved as a natural area, available for the pursuit of

ecological studies. The studies undertaken include intensive

investigations of selected species of vertebrate animals. The main

criteria used in selecting these species have been whether or not they

were sufficiently abundant and generally enough distributed to play an

important role in the over-all ecology of the area, and whether a

species was sufficiently accessible for study with available techniques.

Among the 300 species of vertebrate animals recorded from the

Reservation, the five-lined skink is one of those most frequently

noticed in the field. In actual numbers it is probably exceeded only by

the cricket frog (_Acris gryllus_), the leopard frog (_Rana pipiens_),

the ring-necked snake (_Diadophis punctatus_), the prairie vole

(_Microtus ochrogaster_) and perhaps the white-footed mouse (_Peromyscus

leucopus_). Although numerous, the skink is not easy to study because it

is secretive in its behavior, and is inactive in inaccessible shelters

during the greater part of the year.

The five-lined skink generally occurs along with a characteristic set of

community associates in a particular type of situation. It is a predator

on various small animals, mostly invertebrates. For some of the many

prey species the effect is certainly negligible, but for others its

predation may be a major ecological factor. In areas where optimum

habitat conditions exist its biomass may exceed that of any other

insectivorous animal, and in such situations it assumes a major role as

a predator and as a competitor with other insectivorous types. In turn

it provides part of the food source of various larger predators,

including reptiles, birds and mammals. It is a host and carrier of

various parasites, including at least one species that regularly attacks

humans--the common chigger. It is not evident on the basis of the

present findings that the skink is either harmful or beneficial to any

perceptible degree, in its over-all effect on human affairs and economy.

Nevertheless, there probably are various unsuspected relationships.

In the course of my field study many workers on the University of Kansas

Natural History Reservation helped by capturing skinks; especially

Sydney Anderson, Richard Freiburg, John Hawken, Dennis G. Rainey and

Lewis L. Sandidge. Mr. Robert Gordon very kindly furnished information

on specimens in the Tulane University collection, which served as a

basis for comparing the breeding schedule of the southern population

with that of _E. fasciatus_ in northeastern Kansas. Dr. W. J.

Breckenridge kindly permitted examination of material in the University

of Minnesota Museum of Natural History. Dr. Edward H. Taylor has made

helpful suggestions from time to time. Mr. Richard B. Loomis helped me

in various ways with the field work, and made available his personal

field notes with records of predation on _Eumeces_ by various snakes.

Dr. E. Raymond Hall, Director of the Museum of Natural History, has

critically examined the manuscript, and has been helpful in various

ways. The line drawings and graphs, with the exception of Figures 8 and

9, were made or completed by Mrs. Louise Brunk, artist for the Museum.

The study here reported on was initiated in May 1949, and was continued

through 1950, 1951 and 1952. A few observations made in 1948 have been

included. Various separate items of information obtained in 1953 have

likewise been incorporated especially where histories of individual

skinks are presented, but the manuscript was completed in essentially

its present form in the fall of 1952.

Methods

Skinks were obtained by active search; rocks and boulders were lifted up

and the skinks thus exposed were seized by hand before they had time to

escape. This method was effective when the skinks were using rocks for

shelter and when temperatures were low enough so that they were slow and

sluggish, but in hot weather the skinks were so quick and active that

those exposed usually escaped. Usually skinks could be obtained much

more easily by trapping. At the pond rock pile (Fig. 26), for instance,

shelter was so readily available that the skinks could seldom be caught

by hand. Gallon cans buried with the tops open flush with the surface of

the ground served as pitfalls and were effective when they were

carefully placed, at the bases of rock ledges or logs or stumps, where

the skinks were most likely to fall into them. Most of the skinks

recorded at the rock pile were caught by this method, and sometimes

several were caught together in the same pitfall. Ordinarily each

pitfall was covered with a large flat rock, propped against a nearby

object to leave ample space for the skink to enter beneath it. The rocks

provided protection from direct sunlight, from rain, and from predators.

Still another method of catching skinks was with wire screen funnel

traps (Fitch 1951:77). These funnel traps were of different sizes, and

were made of different kinds of wire mesh. They were set for reptiles

that were mostly larger than five-lined skinks, and those having

quarter-inch wire mesh permitted many of the immature skinks to escape.

Most of these funnel traps were from about one foot long and five inches

in diameter, to about twice these dimensions, with funnel openings about

1.5 inches in diameter. Some made of 1/8 inch wire mesh, six or seven

inches long, and three or four inches in diameter, with funnel openings

only a little larger than the body diameter of an adult skink, were

found to be suitable for skinks of all sizes, and were used successfully

at the pond rock pile. Most of the skinks trapped were adult males, and

they were taken chiefly in May. The funnel traps were generally placed

at the edges of rock outcrops, boulders or logs, where skinks were

likely to be intercepted in their usual travel routes. Each method of

collecting skinks resulted in occasional mortality to them but most

losses were in those caught in funnel traps. In these traps they

sustained rapid loss of moisture, and were usually somewhat desiccated.

Two or more adult males were often caught together, and in most of these

instances the first one caught probably served as bait attracting

another and arousing his pugnacious interest. Injuries were frequent,

and some deaths occurred because in the close confines of a trap the

loser in a fight was unable to escape further attacks.

Most of the skinks caught were examined, and released within a few

minutes. Snout-vent length was measured by holding the skink against a

rigid transparent plastic millimeter ruler and exerting a slight pull on

each end of the lizard until it tired and relaxed its muscles,

eliminating bends and kinks. Even with such precaution, precise

measurements could not be obtained and the readings often varied a

millimeter or more for the same skink measured two or more times on the

same day. Tail length was similarly recorded with separate readings for

the original and regenerated portions. Also recorded were sex (when

discernible), color and pattern, breeding data, injuries, general

condition, and sometimes temperature. Many of the skinks were brought to

the laboratory, and were weighed to the nearest tenth of a gram.

Occasional trips were made to localities away from the Reservation to

collect skinks. Some of those obtained were kept under observation in

terraria where their behavior was studied. Most were preserved and were

used for data on habitat preferences, seasonal changes in the gonads,

size group, stomach contents, and various other items of information.

Description

The scutellation and osteology have been described in detail by Taylor

(1936:39-48 and 199-206) and others, and need not be repeated. The

five-lined skink is slender and elongate, somewhat snake-like (though

much less so than many other skinks) as the head, neck, body, and tail

are not well set off from each other, and the sleek, streamlined

contours are broken only by the small limbs protruding from the sides of

the body. The body is slightly flattened laterally, tending toward

quadrangular shape in cross section. The head is wedge-shaped, with a

short, rounded snout. The nostrils are laterally placed, well back from

the tip of the snout. The eyes are small and deep set; the iris is dark.

The neck is thick and strong, nearly as long as the head. The torso is

3-1/2 to 4 times as long as it is wide. The tail is almost square in

cross section at its base, but is circular in cross section for most of

its length. The limbs are moderately developed; when adpressed along the

sides of the body, the forelimb and hind limb overlap by a length about

equal to the longest toes of the forelimb. The limbs are pentadactyl and

all the toes are well developed and have claws (Figures 1 and 2). The

claws are short, and are curved in such a manner that their tips are

directed downward, each approximately at right angles to the axis of the

toe (Figure 2b). The limbs are moderately thick and muscular. The upper

arm and forearm segments are of approximately equal length, as are the

femoral and tibio-fibular segments of the hind limb.

[Illustration: FIG. 1. Antipalmar view of right front foot, x 9.]

[Illustration: FIG. 2. A. Antiplantar view of right hind foot, x 9.

B. Terminal part of second toe of left hind foot, and its claw, in

lateral view, x 9.]

The five-lined pattern is characteristic of the hatchling, but gradual

ontogenetic change results in its dulling, suppression, and eventual

loss. In the hatchling the ground color of the head and body is black or

dark brown, with five milky white longitudinal stripes extending the

length of the head and body, and on the basal one-fourth of the tail.

The five light lines are of approximately equal width, and are separated

by dark interspaces 1-1/2 to 2 times as wide. The mid-dorsal stripe

includes most of the two mid-dorsal scale rows. Posteriorly it extends

onto the base of the tail, where it becomes increasingly suffused with

the blue color of the tail, widens, and loses its identity. In the

nuchal region, this dorsal stripe narrows and splits into left and right

branches, which diverge anteriorly to form a lyrate pattern on the head.

On either side of the dorsal stripe are the dark interspaces, nearly

twice as wide as the stripe itself and tapering to a point posteriorly

on the tail, likewise tapering anteriorly to a point immediately above

and in front of the eye. Lateral to these dark areas are the

dorsolateral stripes; they extend from the basal one-fourth of the tail

anteriorly onto the head along the superciliary region, tapering to a

point on the anterior superciliary. Below these stripes are the dark

lateral areas which extend from the basal part of the tail anteriorly

along the sides of body and neck region (including the upper half of the

aperture of the ear), eye region, and loreal region. Below this dark

area on each side is the lateral stripe. It extends along the sides just

above the level of the limb insertions (broken or pinched to a fraction

of its average width above the hind limb insertion), broken by the ear

opening, and extending anteriorly to include all the supralabial scales

(with the exception of their upper edges) and the rostral. Here the left

and right lateral stripes may be said to join; however in the facial

region these stripes are not well defined, partly because the dark areas

that border their lower edges do not extend so far forward. This

lowermost dark area is about equal in width to the lateral stripe. It

extends from the posterior infralabials posteriorly, to include the

fore- and hind-limbs, and onto the basal part of the tail. The ventral

surface of the head and body is dull white or pearly gray.

Thus, there are 12 longitudinal bands of color on the body: the five

narrow, subequal, pale lines separated by the six dark areas, of which

the dorsal and dorsolateral are broad and of approximately equal width,

while the ventrolateral is narrower; and lastly the broad, pale ventral

area.

[Illustration: FIG. 3. A. Osteoderm of an old adult male,

from near the midline of the back, x 25.

B. Another osteoderm from same male, from belly near midline, x 25.

C. Another osteoderm from side of same male, at a point

approximately halfway between foreleg and hind leg, x 25.

D. Osteoderm of a juvenile obtained in April, from near midline of

back, x 25.

E. Tongue from dorsal view, shown in its normal position in the

lower jaw, x 2-1/2.]

The tail in young individuals is bright blue. In _Eumeces_ the tail

characteristically has a color different from that of the body, and is

usually more conspicuous; in many species it is blue, but in others it

may be purple, greenish-blue, red, pink, or orange. Hatchlings have the

most brightly colored tails, and as growth proceeds the colors gradually

become duller. In _E. fasciatus_ the bright colors of the tail are

mostly or entirely lost in old adults, especially in males, and in

individuals of either sex that have lost their original tails and

regenerated new tails. Young which lose their tails and regenerate them

at an early age have the regenerated portions colored almost as brightly

as the originals at first.

The skin is tight fitting and relatively thick, stiffened by a bony

armor. A small bony plate or osteoderm underlies each scale. Oliver

(1951:127) has called attention to the pattern of ornamentation on the

osteoderms, which becomes more complex with advancing age. He has

suggested the possibility that age might be accurately determined on the

basis of extent of osteodermal ornamentation. I have compared

osteodermal ornamentation in marked individuals of known age, but have

found it to be of limited applicability as a method of age

determination; size and pattern are probably more satisfactory bases for

estimating age, even though they do not permit definite aging of old

adults and are not infallible for skinks short of adult size. In adult

_E. fasciatus_ the pattern of ornamentation is closely similar to that

figured for _E. laticeps_ by Oliver (op. cit.) and also resembles the

pattern shown for an Old World skink, _Mabuya multifasciata_, as figured

by Smith (1935: 2). The pattern differs somewhat in osteoderms on

different parts of the body, and is most nearly symmetrical in those

near the midline on either dorsal or ventral surface (Figure 3).

Relationships

_Eumeces_ is a widespread genus occurring in the New World in southern

Canada and southward into Costa Rica. The greatest number of forms is in

Mexico. In the Old World numerous species occur in southeastern Asia and

on adjacent islands, and other species occur westward across southern

Asia, and across North Africa to Morocco, with a major break in the

continuity of distribution in the Himalayan region. Taylor in his

revision recognized 57 forms with fifty full species, belonging to 15

major groups within the genus. Since then only relatively minor changes

in classification have been proposed. Several new species and subspecies

have been named, and several species have been relegated to the status

of subspecies.

Within the genus there are several groups that have representatives in

both the New World and the Old World. Smith and Etheridge (1953:159)

point out that the most primitive line of _Eumeces_ is best represented

in the Old World, where there are two groups and nine species, while in

the New World this line has only three tropical relict forms. For this

reason, Smith and Etheridge concur with Taylor (1936:67) in considering

the genus to be of Old World origin; but the two main lines of the

genus (the four-lined and five-lined stocks) are both regarded as being

of New World origin. According to this idea, the Asiatic members of

these two groups migrated from the New World. In the early Tertiary,

warm temperate climates extended north to the Arctic Circle, and

_Eumeces_, or at least some of its species, may have had a distribution

straddling migration routes to both North America and Asia.

Of the 15 groups within the genus, the _fasciatus_ group, with a dozen

species, has more representatives than any other. The _fasciatus_ group

is characterized by having the tail bright blue with dorsal body pattern

of five light lines on a darker ground color; mid-dorsal line

bifurcating on head to form lyrate markings (this striped pattern and

bright color of the tail becoming dull or obsolete in the adults);

medial preanal scales overlapped by those lateral to them; two pairs of

nuchals; no postfemoral pocket; four supraoculars; scales on sides of

body in parallel rows. The characters that separate members of the

_fasciatus_ group from each other are minor. The width and position of

the light lines differ somewhat among them. The mid-dorsal light line

bifurcates either on the nuchals or on the parietals. The complex of

scales in the temporal region differ in shape and relative size.

The following table, compiled mostly from information set forth by

Taylor (1936:186-283), indicates some of the main differences and

similarities between species in the chief characters upon which the

classification is based.

The close resemblance between _E. fasciatus_ and its Asiatic relatives

is remarkable considering the great distance separating them and the

long time that must have elapsed since their isolation began. Some of

the Asiatic forms differ from each other almost as much as they differ

from _fasciatus_. Of the Asiatic species, _elegans_, _tamdaoensis_,

_oshimensis_, and _marginatus_ differ from _fasciatus_ in markedly

larger size; _elegans_, _marginatus_, _oshimensis_, and _stimsonii_

differ in lacking a postnasal; all but _tamdaoensis tunganus_ and

_xanthi_ differ in having only a single postmental; all but _tunganus_,

_E. latiscutatus okadae_ (and sometimes _oshimensis_ and _elegans_)

differ in reduced number of scale rows; all but _tunganus_ differ in

having a lateral postanal scale differentiated, and usually keeled;

_tunganus_, _xanthi_ and _elegans_ differ in having a patch of enlarged

scales on the posterior side of the thigh; and in all, the primary

temporals and upper and lower secondary temporals differ in size and

proportions. Although some of the Asiatic forms seem to be directly

derived from others, _fasciatus_ is somewhat intermediate between the

more divergent forms, and fulfills most of the conditions to be looked

for in an ancestral type.

Table 1. Distribution, Pattern, Size, and Lepidosis of the

"Five-lined" Skinks (Fasciatus Group of the Genus Eumeces)

==================================================================================================================================

|_fasciatus_

| |_laticeps_

| | |_inexpectatus_

| | | |_tunganus_

----------------+---------+---------+---------+----------+--------+---------+-------+--------+---------+-------+-------+--------------

| | | | | | | | | | | |

Juvenal Pattern | 5 | 5 or 7 | 5 or 7 | 5 | 5 | 5 | 5 | 5 | 7 | ..... | 5 | 5

| | | | | | | | | | | |

length in mm | 80 | 130 | 89 | 81 | 76 | 96 | ..... | 99 | 63 | 66 | 93 | 80

| | | | | | | | | | | |

| | | | | | | | | | | |

Postmental | 2 | 2 | 2 | 2 | 2 | 1 | 2 | 1 | 1 | 1 | 1 | 1

| | | | | | | | | | | |

No. scale rows |28-30 |30-32 |30-32 | 28 |22-24 |26-28 | ..... |26-28 | 26 | 22 | 26 |26 (or 24)

| | | | | | | | | | | |

| | | | | | | | | | | |

| | | | | | | | | | | |

Median | | |not | | | | | | not | | |

----------------+---------+---------+---------+----------+--------+---------+-------+--------+---------+-------+-------+--------------

The American _Eumeces laticeps_ and _E. inexpectatus_ seem to be more

specialized than _E. fasciatus_ and might have been derived from it or

from a common ancestor differing but little from the modern _fasciatus_.

Both differ from _fasciatus_ in having more scale rows. _E. laticeps_

also differs in having eight instead of seven supralabials and in having

the median subcaudal scales greatly widened, in having intercalated

plates on the outer side of the fourth toe nearly to the ultimate

phalanx, posterior supralabial low and elongate, young sometimes

seven-lined instead of five-lined, and especially in much larger size,

stocky build, and in early loss of striped pattern. _E. inexpectatus_

differs in having the median subcaudals not at all enlarged, and in

having the dorsolateral stripes a little more widely separated from the

midline.

_Eumeces fasciatus_ and its relatives present a curious exception to

Jordan's Rule, which states that the nearest relatives of any given

species are to be found neither in the same area nor in a remote one,

but in an adjacent region separated by a barrier. _E. fasciatus_ is

absent from almost all of Florida; otherwise its range overlaps most of

the ranges of both _laticeps_ and _inexpectatus_, the former including

the southeastern United States south of about latitude 40 deg., and the

latter being mainly in the Atlantic and Gulf states from Chesapeake Bay

into eastern Louisiana. Presumably both of these species began their

differentiation as southern populations of an ancestral _fasciatus_ and

later became isolated from it and continued their differentiation until

they overlapped it again as distinct species. The differentiation of

_laticeps_, being much greater, presumably took place at an earlier time

than did that of _inexpectatus_, and at present it overlaps _fasciatus_

more extensively. _E. laticeps_ probably diverged to such an extent that

competition with _fasciatus_ is greatly reduced where the two species

occur together.

Since _Eumeces laticeps_ was recognized by Taylor as a species distinct

from _fasciatus_, numerous authors have accumulated field observations

that demonstrate ecological divergence between the two. Conant (1951:33)

wrote that in Ohio _laticeps_ prefers a dry habitat of bare rocks,

cliffs, dry hillsides, and trees. He summed up the habitat difference as

follows: "_Fasciatus_ appears to be essentially terrestrial, to prefer a

moist environment and to be at home in ravines in southern Ohio.

_Laticeps_ on the other hand, is largely arboreal (particularly adults),

prefers dry cliffs, sunny hillsides and hilltops and lives in general

above the habitat of _fasciatus_." Netting (1939:127) likewise states

that in Pennsylvania _E. laticeps_ inhabits drier places than does

_fasciatus_, and is largely arboreal. Other authors with few exceptions

agree that _laticeps_ is largely arboreal, but most describe it as at

home in forest swamps and bottomlands. My own field experience with it

is limited. In the Pigeon Lake area of Miami County, Kansas, the

northwesternmost known locality of occurrence for _laticeps_, the

habitat relations described by Conant for Ohio were almost reversed.

_Eumeces laticeps_ was relatively scarce, and confined to the vicinity

of the swamp chiefly in areas that are flooded in time of high water.

All those seen were on or near massive snags of dead trees still

standing, but decayed and honeycombed with cavities. Slabs of bark

clinging loosely to the tree trunks, with spaces beneath, provided

shelter for the skinks and for the abundant arthropod fauna which

probably constituted their chief food source. This is one of the few

places in Kansas where a remnant of the original bottomland forest

remains. In central Louisiana, in 1947 and 1948, persons living on the

Kisatchie National Forest told me of large, red-headed skinks living in

hollow trees, which must have been _E. laticeps_. In the literature _E.

laticeps_ is frequently referred to as red-headed, although the reddish

suffusion on the head of the adult male is ephemeral in this species as

it is in _E. fasciatus_ and others. The heightened activity of the adult

males in the breeding season seems to have drawn attention to this

conspicuous temporary coloration while its absence at other seasons has

scarcely been mentioned.

Mansueti (1948:213) describing the habits of _laticeps_ in Maryland,

Louisiana and elsewhere in the southern states, emphasizes its arboreal

habits, referring to it as "'scorpion' of the treetops." He describes it

as dashing up and down tree trunks, along fences, and in abandoned

buildings. However, he states that it also spends much time on the

ground, and may take refuge in holes and cracks near ground level, and

gravid females are less arboreal, making their nests in decayed logs of

chestnut or oak. He mentions individuals having been found living far

above ground in tall trees, in nests of birds of prey. One old male that

was frequently seen by him always retreated far up a dead chestnut tree

that towered above the surrounding forest of scrub pine. Mansueti also

mentions arboreal combats between males and implies that they are

territorial. Taylor (1936:59) described _laticeps_ as typically an

arboreal form, almost invariably found in trees, and he indicated that

it has claws more curved than in other species--an obvious arboreal

adaptation. Parker (1948:25), however, stated that "_E. laticeps_ is

reputed to be rather arboreal, but field work in western Tennessee has

not borne out this belief. A few of the specimens have been found in

tall, dead trees, as has _E. fasciatus_." This statement evidently was

based on a small number of observations.

Cook (1943:15) mentions a female _laticeps_ found in a nest with a

clutch of 27 eggs (hence certainly a communal nest of two or more

females) in a burrow under a log, on July 8, 1941, in Lee County,

Mississippi. This account is under the name _Eumeces fasciatus_ but the

large size of the female precludes the possibility of it being either

_fasciatus_ or _inexpectatus_. The remainder of Cook's account is

evidently based on a composite of observations on all three species.

Goin and Goin (1951:29-33) have given an excellent brief account of

behavior and seasonal schedule in a small colony of _E. laticeps_ near

Gainesville, Florida, based on almost daily observations over a period

of years. In view of the greatly different climatic conditions, the

seasonal schedule is remarkably similar to that of _E. fasciatus_ in

Kansas, and it seems that the minimum threshold temperatures required

for activity are much higher in _laticeps_. Temperatures of 80 deg. F. or

above for several consecutive days seemed to be a necessary stimulus for

emergence from hibernation; emergence was in the last week in March or

the first week in April in Florida. Hatching was found to take place in

late June or early July. Adults were last seen before retiring into

dormancy in the latter half of September and young of the year remained

active into October some two or three weeks later. The skinks observed

all lived in hollow water-oaks. When the population was at an especially

high level, in the late summer of 1949, each hollow oak was inhabited by

one young and one adult. Territoriality and mutual exclusiveness of

adults and even of young seems to be implied. The skinks were seen

eating spiders, ants, and cockroaches.

Neill (1950:115) mentions one sizable colony of _E. laticeps_ living in

a treeless urban area, in Georgia and depending for shelter on piles of

metal drums and other industrial equipment. Evidently, however, this was

an exceptional situation. In another paper, Neill (1948b:109) described

the specialized hibernation site requirements of _laticeps_ in Georgia;

the skink retires inside large, rotting pine stumps, especially those

that are leaning. He states (1948a:157) that in Georgia, _laticeps_ is

most common in the Coastal Plain and is much less numerous above the

Fall Line (the line between the Coastal Plain and the Piedmont). Deckert

(1918:31) wrote of "_Plestiodon fasciatus_" in the vicinity of

Jacksonville, Florida, where only _E. laticeps_ and _E. inexpectatus_

occur: "Inhabits hollow trees, always near water. Blue-tailed ones often

live around human habitations."

With regard to the ecological traits of _E. inexpectatus_ that

distinguish it from _fasciatus_, authors are much less definite, and

evidence is somewhat conflicting as the differences are relatively

minor. Engels (1949:269) noted the occurrence of _E. inexpectatus_ on

two low islands of submarine origin, off the North Carolina Coast,

Harkers Island and Shackelford Banks, and he surmised that the absence

from them of _E. fasciatus_ and _E. laticeps_ must have some ecological

significance, since all three species occur on the adjacent mainland.

Most of the island _inexpectatus_ were taken from beneath loose bark of

standing trees, while mainland _fasciatus_ was taken from beneath loose

bark of fallen trees.

Barbour and Carr (1940:129) wrote of _inexpectatus_ in the vicinity of

Miami, Florida: "... it seems to be the only one [of the five-lined

skinks] which has adapted itself to life under the rather specialized

environmental conditions existing in its rocky and decidedly tropical

habitat. It is one of the very few forms which have established

themselves on some of the waterless and poorly vegetated islands on both

coasts of the peninsula. _E. inexpectatus_ is much less arboreal than

either _laticeps_ or _fasciatus_. Although it climbs trees when pressed,

it is usually found on the ground among leaves or about fallen logs, and

particularly about stone walls or old buildings made of cut rock."

On the other hand, Neill (1948a:157) states that in Georgia,

_inexpectatus_ is often observed basking on tree trunks, and though

adults often forage on the ground, they dash for the nearest tree when

disturbed, usually climbing to a considerable height before halting. The

juveniles, however, are said to climb only rarely; they hide beneath

objects on the ground when they are pursued. Neill stated that _E.

inexpectatus_ occurs in dry pine forests where _laticeps_ and

_fasciatus_ are lacking, as well as in moist or even swampy woods. _E.

inexpectatus_ often forages on the sides of old buildings.

Hoffman (1953:172), in discussing means of differentiating between

_inexpectatus_ and _fasciatus_ in Virginia, states that there are ample

differences in color and behavior as well as in scalation. He describes

the color difference (blue color of tail of juveniles extending

anteriorly beyond pelvis; light stripes reddish-orange on head,

sublateral line present, in _inexpectatus_) but he does not describe the

differences in behavior. He states that _inexpectatus_ is the most

abundant lizard in southeastern Virginia. Carr (1940:76) also states

that _inexpectatus_ is less arboreal than _laticeps_ and is often found

under logs and boards in dry sand.

_E. inexpectatus_ thus seems to be adapted to a somewhat drier, more

open, habitat than that typical of _fasciatus_, but it is not clear

whether either species is more arboreal in habits. It is to be hoped

that the present inconclusive summary will draw attention to the problem

and will lead to more critical comparisons of the habitats and behavior

of the two species by herpetologists in the southeastern states. The

differences, both ecological and morphological, that distinguish

_inexpectatus_ from _fasciatus_ are of a degree usually found between

subspecies of the same species. The extensive geographic overlap between

them is indeed remarkable in view of the slight degree of

differentiation, morphologically and ecologically. They are, however,

complementary in part in their ranges, while _laticeps_ shares all parts

of its range with either one or the other, or both of them (see Figures

4 and 5).

[Illustration: Fig. 4. Geographic distribution of _Eumeces

inexpectatus_, as indicated by published records; only marginal

and near-marginal records are shown, excluding those of doubtful

validity.]

Under present conditions, with these three species so similar in habits

and so extensively overlapping in geographic range, it is difficult to

visualize a barrier such as would have been required for allopatric

speciation of the type, usual in vertebrates, to have occurred. One

might be tempted to postulate sympatric speciation, with the parent

form, presumably _fasciatus_, giving rise to the other two by abrupt

mutations. However, the demonstrable antiquity of the five-lined skinks

would allow ample time for divergence, allopatric speciation, and

subsequent disappearance of the barrier and intermingling of

populations. The displacement of floras and faunas that occurred in the

Pleistocene, with the successive advances and retreats of the

continental ice sheets might have had some part in bringing about the

present overlapping distribution, after the disappearance of the

original barrier. Such a barrier might have been an eastward extension

of the central grasslands to the Atlantic Coast at a time when the

climate of the continent was warmer and drier.

[Illustration: Fig. 5. Geographic distribution of _Eumeces

laticeps_, as indicated by published records; only marginal and

near-marginal records are shown, excluding those of doubtful

validity.]

Habitat and Limiting Factors

TEMPERATURE AND MOISTURE RELATIONS

For approximately half the year, at the latitude of northeastern Kansas,

five-lined skinks are dormant. In early fall, even before the advent of

cold weather, they are hard to find apparently having begun their

retirement into the sheltered situations where they spend the winter,

even though they may not be fully dormant at that time.

Remarkably little is known of the hibernation habits of this species or

of reptiles in general for that matter. The limit of tolerance to low

temperatures, the type of insulating medium, the moisture relationships,

the specific stimuli which cause the animal to retire to its hibernation

site or to emerge from it have not been determined. On only a few

occasions have natural hibernating sites or the dormant skinks in them

been observed by zoologists. Linsdale (1927:78) recorded one found in a

sawdust pile late in the winter of 1924 in Doniphan County, Kansas.

Hamilton (1948:211) found skinks of this species hibernating in Grant

Parish, Louisiana, in hollow logs 18-20 inches in diameter, five in one

log and three in another, on January 23, 1943. Frost in the damp wood

almost reached the lizards, which were in a torpid condition. These

observations were made when the temperature was 36 deg.F. after the weather

had begun to moderate following an unprecedented four-day cold wave when

temperatures dropped to within a few degrees of 0 deg.F. In both logs the

skinks were accompanied by hibernating anoles (_Anolis carolinensis_).

Neill (1948b:109) in Richmond County, Georgia, found _E. fasciatus_

hibernating in old stumps, fallen timber, piles of debris, or beneath

rocks and ground litter. Beneath scraps of rotting wood he often found

dead, frost-rimmed specimens which apparently had frozen to death.

Hibernating skinks of this species were found singly or in pairs. Some

were not fully dormant when found but could only gape and twist when

uncovered.

Of hibernating _E. laticeps_, Neill wrote, "Many examples are covered

with a waxy exudation, which I believe to be a secretion of the lizard

itself, rather than of the surrounding medium. This exudation has been

noted in other species also." Scott and Sheldahl (1937:192) described a

hibernating aggregation of _Eumeces septentrionalis_ found in Palo Alto

County, Iowa, on February 15, 1937, as follows: "The skinks were found

beneath a ledge of yellow clay about four and one-half feet below the

surface. The lizards, 52 in number, were assembled in a compact group

about the size and shape of a football. A soft, web-like material

surrounded the mass and adhered to the bodies of the animals. Upon being

uncovered some of them exhibited signs of life; others were dead."

Breckenridge (1943:595) reported that a gravel digging crew found

hibernating _E. septentrionalis_ in late October and in January at

depths of two feet (one), and three feet (groups of three and eight).

Tihen (1937:405) recorded that two five-lined skinks found on January

13, 1948, were hibernating eight feet underground at Ranson, Ness

County, Kansas. This locality is far to the west of the main range of

_fasciatus_. Conant (1951:30) mentions the finding in Ohio of a young

blue-tailed skink under a log where it seemed to be hibernating, on

January 22. The spot where it was resting was soggy, and surrounding

areas were covered with several inches of water.

In the course of the present study, no five-lined skinks were found

hibernating under natural conditions, but on numerous occasions in early

spring, two or three or four skinks were found together under massive

flat rocks in semi-torpid condition, beside deep holes or crevices which

presumably led to their hibernation sites in better insulated cavities.

In the winter none could be found in such situations under large rocks,

nor in the superficial types of hibernation sites described by Neill and

Hamilton in the southern states. In the more severe winter climate of

Kansas better protected hibernation sites are required. In the rock

ledge situations where skinks were studied, excavation for the purpose

of finding hibernating individuals was not practical.

On several occasions when skinks were put in the freezing compartment of

a refrigerator and frozen solid, at temperatures several degrees below

freezing, they failed to revive when warmed. However, they can survive

temperatures a little below freezing. On April 1, 1953, one was placed

in the freezing compartment with a thermometer inserted rectally. After

2-1/2 hours when the compartment was opened, this thermometer showed a

temperature of -2.5 deg.C, after a delay of several seconds in obtaining a

reading because of condensed moisture on the thermometer obscuring the

mercury column. Another thermometer that rested beside the skink in the

compartment showed 27 deg.F. The skink was limp and immobile. It was placed

on a table top at normal room temperature, and it warmed rapidly. When

it had reached 1.5 deg.C, it contracted its muscles in response to a light

pinch. At 9.5 deg.C it raised its head and had its eyes partly open. Twenty

minutes after its removal from the freezing compartment, it was still

lying in the same position, its temperature having reached 13.5 deg.C. When

handled it seemed dazed for several seconds as if just awaking. Then it

crawled away briskly.

On March 28, 1953, a skink was placed in the freezing compartment for

about 10 minutes, and upon removal its temperature was recorded as

-0.5 deg.C. It was not frozen, but was limp and unresponsive to such stimuli

as pinching or pricking. At 1.5 deg.C feeble movements of the legs were

noticed. The eyes were still closed. At 3.4 deg.C the legs moved as if in

walking. At 6.0 deg.C the skink raised its head and took several steps

forward. At 7.5 deg.C it protruded its tongue and dragged itself about for

several steps. At 9.0 deg.C movements of the sides indicated an inspiration

approximately every three seconds. At 12.2 deg.C it opened its eyes.

On March 25, 1953, a skink that I had caught the day before and left

overnight in an unheated room, was found to have burrowed into loose

earth in its container. When exposed, its temperature was 1.8 deg.C and it

was unable to crawl normally, but took only one step at a time, and

progressed with slow lateral squirming motions. Placed on the ground

outside the building, in the shade where there was still a little frost,

it moved forward persistently for several inches trying to burrow into

the surface litter. After a few minutes, its eyes were shut and it

seemed incapable of further locomotion. Its temperature was 1.4 deg.C. When

placed on its back it was able to turn over slowly after several

seconds. A few minutes later its temperature was 0 deg.C, and it was totally

helpless, although still capable of feeble movement. When stimulated by

touch, it flexed its body a little, or moved each limb slowly in an arc

as if walking, the movement taking several seconds. Placed on its back

or side it was unable to right itself.

Less than three hours later I saw a skink that was active in the field.

Slight movement at the edge of a rock that was exposed to sunshine

attracted my attention and turning the rock I found the skink

underneath, lively enough to scramble for shelter but slow and stiff

compared to those that are fully active. Its temperature was 13.5 deg.C and

air temperature was 7.5 deg.C. In damp soil beneath the rock where the

lizard was found, temperature was only 5.7 deg.C. It seemed that the skink

had been sufficiently warmed by contact with the undersurface of the

rock to move into the open, and was just emerging when I approached.

After capturing the skink, I set it on a rock in the sunshine, and in

five minutes its temperature had risen to 26 deg.C.

As compared with its reptilian associates in northeastern Kansas,

_Eumeces fasciatus_ is outstanding in its ability to become active and

carry on normal activities at relatively low air temperatures. In spring

it is usually seen in the open before any other kind of reptile, because

it has the capacity to move about sluggishly at temperatures so low that

some other reptiles are numbed and completely immobilized, and because

it has small size enabling it to make rapid adjustment upward by

insolation, or contact with sunshine-warmed surfaces. By virtue of this

ability it has been able to extend its range farther northward than most

other reptiles, and it has gained the advantage of a longer growing

season. This advantage was especially apparent in the spring of 1953. A

mid-March warm spell with seven out of eight successive days having

maximum temperatures in the sixties culminated on March 20, with a

maximum air temperature of 82 deg.F. This warmth was sufficient to activate

most of the five-lined skinks, and a few reptiles of other kinds. After

the unseasonably high temperature of March 20, there was rapid return to

cooler weather with temperatures frequently below normal throughout

April. As a result there was little activity of other kinds of reptiles

that month, but five-lined skinks were active on most days. On only a

few days, those with temperatures in the low forties or those on which

the sky remained overcast, did the skinks remain inactive. On most days

maximum temperatures were in the fifties and sky was clear. Under these

conditions the skinks were able to emerge and bask, rapidly raising

their body temperatures far above those of the air and substrate.

By the end of April some kinds of deciduous trees have not yet begun to

leaf out, and in most other kinds the leaves are still in an early stage

of development. Absence of a leaf canopy during April permits the skinks

to utilize the spring sunshine to maintain their body temperatures at

almost the same high level that they maintain in the same situations in

hot summer weather.

Table 2. Temperatures (in Degrees Centigrade) of Skinks Found Under

Flat Rocks Exposed to Sunshine, Contrasted With Air Temperatures;

Spring of 1953.

==========+==========+============+===========+

| Age | Skink | Air |

Date | and sex |temperature |temperature|

----------+----------+------------+-----------+

March 23 | Ad. [F] | 20.8 | 12.4 |

March 23 | young | 24.7 | 12.4 |

March 25 | Ad. [M] | 22.8 | 12.5 |

March 25 | young | 21.0 | 12.5 |

March 25 | young | 25.7 | 14.5 |

March 25 | young | 22.5 | 14.5 |

March 27 | Ad. [M] | 26.6 | 16.5 |

March 27 | young | 22.0 | 16.5 |

March 27 | Ad. [F] | 22.5 | 16.5 |

March 27 | Ad. [F] | 20.5 | 16.2 |

March 27 | Ad. [F] | 26.5 | 19.3 |

March 27 | Ad. [F] | 30.7 | 19.3 |

April 4 | young | 22.0 | 18.1 |

April 5 | Ad. [F] | 26.0 | 13.0 |

April 6 | Ad. [M] | 31.5 | 13.5 |

April 6 | Ad. [M] | 23.7 | 16.0 |

April 6 | Ad. [F] | 22.2 | 16.0 |

April 6 | Ad. [M] | 20.0 | 16.0 |

April 6 | Ad. [F] | 20.0 | 16.0 |

April 6 | Ad. [F] | 26.5 | 20.3 |

April 20 | Ad. [F] | 29.7 | 17.2 |

April 20 | Ad. [F] | 25.8 | 17.2 |

----------+----------+------------+-----------+

Life History and Ecology of the Five-Lined Skink, Eumeces fasciatus · 第 1 / 16 段