genus _Phidippus_, 5 lycosids, 4 thomisids, and the remainder
unspecified); 15 insect larvae (7 of them lepidopteran and one
tentatively identified as an ant, _Camponotus castaneus_, the rest
unspecified); 13 unspecified insects; 10 crickets; 9 roaches; 9 snails
(5 of them _Gastrocopta armifera_); 7 beetles; 4 sloughs of skinks; 3
grasshoppers; 2 grouse locusts; and one each of cave cricket
(_Ceuthophilus?_), ant (_Camponotus castaneus_), moth, centipede, sow
bug, and egg of a skink. The egg was probably laid by the female that
ate it, since she was found brooding an unusually small clutch of only
three eggs.
The condition of food items found in stomachs varied greatly. Some were
nearly intact, while others were fragmentary and represented by only a
few of the more durable and indigestible parts. The larvae of various
insects found in stomachs examined are especially noteworthy, since but
little comparable material was found in the much larger group of items
identified from scats.
The scatological material was even less satisfactory than the stomach
material in providing determinable food items. The scats of these skinks
are, roughly, 10 to 20 mm. long and two to four mm. in diameter, usually
cylindrical and almost straight, and capped at one end with a white
chalky deposit of uric acid. Superficially they have some resemblance to
bird droppings, but are different in texture. The uric acid deposit is
loose and crumbly, and much less compact than that with bird feces, and
the food residue is much less completely disintegrated than is similar
material in feces of birds. Common small snakes which might produce
feces of similar size, include the ring-necked snake (_Diadophis
punctatus_), the worm snake (_Carphophis amoenus_), and DeKay's snake
(_Storeria dekayi_), but their feces have a much higher moisture
content, lack the definite shape of the skink scats, and ordinarily do
not contain readily recognizable residue of the prey. The six other
species of lizards on the Reservation, the collared lizard (_Crotaphytus
collaris_), brown skink (_Scincella laterale_), prairie skink (_Eumeces
septentrionalis_), Sonoran skink (_E. obsoletus_), six-lined racerunner
(_Cnemidophorus sexlineatus_) and glass "snake" (_Ophisaurus
attenuatus_) might produce scats indistinguishable from those of the
five-lined skink. However, none of these lizards except the relatively
rare and secretive brown skink, occurred in either of the two situations
where most of the scats were collected and it is highly improbable that
the scat collection included any material from species other than the
five-lined skink.
The scats consist mainly of chitinous fragments of arthropod prey.
Usually the prey fragments are so well comminuted, mixed, and scattered
that reconstruction is difficult. Degree of disintegration differs
greatly, depending not only on the type of prey eaten, but probably also
on the condition and temperature of the lizard, and the amount of other
food in its digestive tract. Arthropods which have recently undergone
ecdysis and have the exoskeleton still thin and soft are no doubt
digested much more completely than those that have more heavily
sclerotized parts. In spiders the chelicerae are more resistant to
digestion than are other parts of the exoskeleton, and frequently
appear, intact or nearly so, in the scat contents. The fangs being even
more resistant, were sometimes found separately when no other cheliceral
parts were recognizably preserved. Frequently large fragments of the
carapace, with some of the eyes or all of them, were found. Spider
abdomens sometimes were distinguishable, but were collapsed and
compressed. Spider legs conspicuous in most of the scats, were so
broken, tangled, and distorted that they were of little diagnostic
value. In harvestmen, dorsal shields were nearly always fairly intact;
but only small fragments of the elongate slender legs were found and
they were mostly broken off when the attacking skinks battered the
phalangid against the ground before swallowing it. The horny outer wings
of crickets, roaches, and beetles usually were in recognizable though
fragmentary condition. Occasional heads of insects often were found
fairly intact. Insect legs were sometimes intact, sometimes broken into
sections or crushed and fragmented. The thorax was usually represented
by scattered fragments of chitin, and the abdomen by the separate chitin
bands of each body segment.
Shells of snails were sometimes found nearly intact in the scats,
although showing the effect of the digestive juices in their extreme
brittleness. In other instances all that remained of the shell was the
inner columella, and small scattered fragments.
Certain of the items eaten were probably so thoroughly digested as to
leave either no hard parts at all, or minute and nondescript parts that
were not recognized. The common small slug _Deroceras laeve_, for
instance, would seem to be just as suitable and available for food as
the various kinds of snails, but it was not recorded in either stomachs
or scats. Having no hard parts except the vestigial internal shell, it
probably would not be recognized in scats, even though it had been
eaten. Various insect larvae, having thin outer cuticles and virtually
no hard sclerotized structures except in the head, likewise probably
would leave no recognizable parts. Molted skin of the skinks themselves
seemed to be little altered by the digestive processes.
Table 16. Frequency of Occurrence by Months of Various Types of Prey
in a Collection of 371 Scats of Eumeces fasciatus.
=========================+========+======+======+======+=======+=======
| May | | | | |
| (and | June | July | Aug. | Sept. | Total
| April) | | | | |
-------------------------+--------+------+------+------+-------+-------
Spider | | | | | |
unspecified | 32 | 32 | 16 | 100 | 10 | 190
salticid | 10 | 18 | 5 | 31 | 7 | 71
lycosid | 7 | 1 | 3 | 18 | 4 | 33
Harvestman (phalangid) | .... | 7 | 1 | 16 | 2 | 26
Orthopteran | | | | | |
unspecified | .... | 4 | .... | 14 | .... | 18
cricket (ceuthophilid) | .... | 6 | 11 | 31 | 2 | 50
cricket (gryllid) | 2 | 1 | .... | 16 | 1 | 20
grouse locust | 3 | 2 | .... | 17 | 2 | 24
grasshopper | .... | .... | .... | 6 | .... | 6
roach | 1 | 2 | .... | 2 | .... | 5
Beetle | 4 | 13 | 1 | 11 | 2 | 31
Ant | .... | .... | 1 | .... | .... | 1
Wasp | 1 | .... | .... | 1 | .... | 2
Caterpillar | 1 | .... | .... | 1 | 1 | 3
Other insects | 3 | 8 | 6 | 45 | 5 | 67
Five-lined skink | | | | | |
slough | 2 | 1 | 3 | 12 | 1 | 19
hatchling | .... | .... | .... | 1 | 1 | 2
Snail | | | | | |
unspecified | 3 | 6 | 6 | 8 | 6 | 29
_Gastrocopta_ | .... | 2 | .... | 8 | 1 | 11
_Retinella_ | 1 | 1 | .... | 6 | .... | 8
+--------+------+------+------+-------+-------
Total | 70 | 104 | 53 | 344 | 45 | 616
-------------------------+--------+------+------+------+-------+-------
The collection of 371 skink scats originated mainly from two places on
the Reservation nearly three-quarters of a mile apart, the pond rock
pile and an old wooden bridge across a ravine. On the weathered planks
of the bridge, the scats were conspicuous and could be easily gathered
in quantity. At the pond rock pile, where skinks were especially
abundant and were intensively studied, their scats were frequently
noticed on the large rocks where they hunted and basked. A third smaller
collection of scats was made in the vicinity of the laboratory buildings
and adjacent rock walk frequented by a few skinks. A small number of
additional scats were collected elsewhere on the Reservation, but
ordinarily the scats were so inconspicuous in the woodland situations
where skinks occurred under typical habitat conditions, that few were
found. The rock pile, bridge, and vicinity of buildings are not typical
of the species' habitat and might offer somewhat different choices of
prey items.
The 30 scat collections were made in 1951 and 1952. Seasonally, the
sample of scats overlapped but little the sample of stomach contents,
and was concentrated in the latter half of the growing season. The
distribution by months was as follows: April-2; May-38; June-60;
July-29; August-213; September-26. Most of the scats probably were
deposited within a few days of the time they were collected, because
scats disintegrate and disappear rapidly in the field where they are
exposed to rain, wind and dung-feeding insects.
No clearly defined seasonal trends are revealed in Table 16 but the
monthly samples, except that for August, are scarcely adequate for this
purpose. Approximately equal numbers of scats were collected at the two
main stations, the pond rock pile and the bridge, but some kinds of
items were unequally represented in the two samples.
Table 17. Comparison of Frequency of Occurrence of Various Food
Items in Two Different Small Areas, Based on Scat Analysis.
======================+=================+=================+==================
| Total from | Percentage of | Percentage of
| both collecting | total in bridge | total in pond
| stations | sample | rock pile sample
----------------------+-----------------+-----------------+------------------
Spiders (all) | 292 | 63.3 | 36.7
salticids | 67 | 79.2 | 20.8
_Phidippus audax_ | 16 | 100.0 |
_Phidippus sp_ | 3 | | 100.0
lycosids | 33 | 36.3 | 63.7
harvestmen | 28 | 57.1 | 42.9
ceuthophilids | 39 | 30.8 | 69.2
grouse locusts | 25 | 92.0 | 8.0
crickets | 26 | 42.3 | 57.7
snail | 34 | 61.9 | 38.1
_Gastrocopta_ | 11 | 91.0 | 9.0
_Retinella_ | 6 | 50.0 | 50.0
----------------------+-----------------+-----------------+------------------
Spiders, harvestmen, and snails were well represented in both samples.
In the bridge sample, salticids (especially _Phidippus audax_), grouse
locusts, and the snail _Gastrocopta_ were more numerous. In the rock
pile sample lycosids, and especially ceuthophilid crickets were more
abundant. The ceuthophilids were notably numerous among the rocks, and
many of them were caught in the wire funnel traps placed there for
skinks.
Little is known concerning the quantitative food requirement of any kind
of lizard. Five-lined skinks fast for at least half the year during the
period of dormancy, from September to April. When they emerge from
dormancy in spring most of them are plump and appear to have lost little
weight in the course of their long fast. In the season of activity,
obviously the quantity of food consumed fluctuates according to
temperature and activity of the lizard. Most of the prey taken falls
within a fairly narrow size range. The prey ordinarily is swallowed
entire or nearly so. This imposes a definite upper size limit. The skink
of course lacks the ophidian capacity to ingest relatively enormous
objects. The mental symphysis and pectoral girdle would prevent
ingestion of an object much larger than the skink's body diameter, but
soft-bodied and flexible arthropods of body diameter approximately equal
to that of the skink may be ingested. Typical food items are of such
size that from one to three of them fill the stomach to capacity. On one
occasion, in an attempt to feed a brood of young recently hatched in the
laboratory, I dropped into their jar a mass of newly hatched house
spiders (_Theridion tepidariorum_). As these minute spiders swarmed over
and around the skinks, the lizards gave little heed to them except
occasionally to jerk or scratch in irritation. One skink, however, was
seen to snap up a spider which ran near its snout. The adult female
_Theridion_ from the same web was then introduced into the skinks' jar,
although it seemed too large prey for these small lizards, as its
abdomen was fully as large as their body diameter. When it ran, the
hatchling skinks immediately became alert and several chased it biting
at it in frantic excitement. They had difficulty in grasping its smooth
rounded surface, but eventually one did catch it and eat it. Full-grown
mealworms averaging 26 mm. in length, and approximately .11 grams, are
somewhat smaller than the usual prey of adults. In captivity hungry
adult skinks took from one to nine such mealworms at a meal. However,
they could not be induced to feed daily over periods of weeks, even when
kept at high temperatures. Over a period of 64 days an adult male kept
at approximately 80 deg. F. in the daytime and 10 to 15 degrees lower at
night, ate a total of 30 mealworms, which, in the aggregate, weighed
approximately 42 per cent of his body weight. In 35 days under the same
conditions an adult female ate 24 mealworms, approximately 32 per cent
of her body weight.
[Illustration: FIG. 26. Map of University of Kansas Natural History
Reservation showing locations of the four study areas (shaded)
where most data on five-lined skinks were obtained.]
Predation and Parasitism
ESCAPE REACTIONS
Like other members of the family Scincidae, _Eumeces fasciatus_ tends to
be secretive in its habits and it depends on concealment rather than
speed, aggressive behavior, or noxious qualities to escape its enemies.
As compared with lizards in general, or with other members of the genus
_Eumeces_, five-lined skinks are relatively unspecialized in their
behavior, and retain a good deal of versatility. While primarily
terrestrial, they are able to burrow and climb. Their reactions toward
prey and natural enemies vary greatly according to circumstances.
They are less secretive than many other kinds of skinks. Nevertheless
the numbers active on the ground surface at any one time, even under the
most favorable weather conditions, probably are only a fraction of the
total population. For instance, in two or three hours of intensive
search in Skink Woods, in which almost every square yard of the area was
inspected, a dozen skinks constituted an unusually good catch. Seldom
were as many as 20 seen--and most of these only when uncovered in their
hiding places. At the pond rock pile, often half a dozen or even more
could be seen simultaneously or within the course of a few minutes, as
they basked or darted about over the rock surface. These, however,
represented only a small part of the number known to occur in the rock
pile, which could be observed in its entirety from one spot. At other
times, especially in late summer and early fall, even when weather
seemed favorable, cursory search of each of the study areas failed to
reveal a single individual. Presumably at such times the majority of
individuals of the dense population were sheltered deep underground in
relatively inaccessible hiding places. Others which escaped attention
may have been climbing on tree trunks or logs, or may have been foraging
on the ground but close to hiding places into which they darted
undetected. The habit of "freezing" in response to a potential danger is
commonly noticed in these skinks, and usually it is effective in
concealing them.
Having elongate bodies and short limbs, five-lined skinks are not
especially swift of foot, but the jerkiness of their movements provides
compensatory elusiveness. One sufficiently warm to be fully active is
nervous in its actions. Even when resting or basking it is likely to
shift its position frequently, fidgeting, blinking, and panting,
obviously on the alert for any sign of danger. In moving about, it
usually progresses only a few steps at a time, with frequent pauses
sometimes only a fraction of a second in duration. These numerous stops
allow the animal to examine the terrain immediately ahead of it, and
perhaps avoid blundering within reach of a lurking enemy.
Ontogenetic change in the color pattern is of significance in connection
with the secretive habits. The red facial suffusion of the breeding male
renders him more conspicuous in his natural surroundings, but this
bright color is ephemeral. It is developed as a warning, for display to
other males. Otherwise, in the adult male the color of dull brown is
inconspicuous in its natural surroundings, usually against a background
of leaf litter, dead stems, and soil. In the juvenile the contrasting
pattern of dark brown ground-color, five longitudinal light stripes, and
a vivid blue tail, is far more conspicuous. The young skink might seem
to be handicapped in its chances for survival by this conspicuousness.
However, in snakes it has been shown that a vivid striped pattern,
characteristic of forms that are fast moving and live in dense
vegetation, serves to conceal motion, and aid its possessor in confusing
and eluding pursuers. The young skinks, being far more active than the
adults, may use the striped pattern more effectively in this way. Often
when a young skink is startled in its natural surroundings, and takes to
cover, the observer does not see its outlines at all, and is conscious
of it only as a flash of blue. On many occasions, while walking in the
woods, I have had my attention attracted by a faint rustling of dry
leaves, and have received such a fleeting impression of the flashing
blue tail as to be uncertain whether or not I had actually seen a skink,
until, raising a flat rock or other shelter, I found that one actually
was present, concealing itself in the nearby hiding place. The erratic
movements of a frightened skink that is warm and fully active, make it
exceedingly elusive. With sudden lashing movements of its heavy tail and
hindquarters, it may flip its body about, facing first in one direction
and then in another, as it pauses before or after a rush for shelter.
The sudden reversals of direction are so confusing to the pursuer that
the skink may often escape by hiding after a few seconds of pursuit,
even though the situation provides no shelter where the lizard is
entirely secure. The tail-flip described is characteristically given at
the instant the lizard reaches shelter such as a crevice, or hole, and
just before it disappears. By the instantaneous pivoting of its body,
throwing its tail in an arc, in the direction of its original course,
the lizard creates the optical illusion of having moved beyond the point
where it has taken to shelter. The peculiar writhing movements of the
tail of juveniles that are moving about in the open accentuate the
conspicuousness of the vividly colored tail, and suggest that this
conspicuousness may be advantageous to the lizard in serving as a decoy
to catch the attention of predators and distract them from the lizard
itself.
In hatchlings the mortality rate is high. Tails are broken frequently in
those that survive, suggesting that the tail may be useful in diverting
enemies from the lizard itself. Among 121 young of the smallest sizes,
(snout-vent lengths in the range of 23 to 29 mm.) 7.4 percent already
had broken tails (not including, of course, those in which the tails
were broken while the skinks were being captured). In slightly larger
young, those in the 30-34 mm. range, perhaps averaging one month old,
nearly one-fourth had lost their original tails. In those in the 35-55
mm. size class, mostly one to three months old, about half have already
lost parts of their original tails. In those that are in the size group
65-69 mm. normally attained at an age of a year, approximately
three-fourths have regenerated tails, and in adults the proportion with
unbroken tails is even smaller--down to 16.5 percent in females of more
than 75 mm. snout-vent length. In adults the incidence of broken and
regenerated tails is slightly higher in females than in males. Defense
of nests and sluggishness in the females during the time that they are
excavating the nest burrows and guarding their eggs may result in their
tails being broken more frequently.
Tree-climbing is a common means of escape and it is curious that many of
those who have described the habits of _E. fasciatus_ have either failed
to note it at all or have minimized arboreal habits. Taylor (1936:59)
cited two instances of tree-climbing but stated: "Only rarely is this
form seen in trees, at least in the western part of its range." Conant
(1951:30) stated: "They seldom climb trees, contrary to the habit of
_laticeps_ and _inexpectatus_." Hudson (1942:42) mentioned seeing an
adult that escaped by climbing the side of a hollow tree in southeastern
Nebraska.
In the present study, tree-climbing as a means of escape was observed
frequently, probably more than two hundred times in all. It was
characteristic of both sexes and all ages, and was one of the commonest
responses to danger. In summer when skinks were fully active, they
usually moved too rapidly to be caught by hand either in the open or
where they were uncovered when I turned over rocks or other shelter. To
obtain specimens in any numbers at such times, an understanding was
essential of the somewhat stereotyped behavior pattern involved in their
escape by tree-climbing. A skink that was alarmed in the course of its
foraging or basking on the ground litter was likely to run directly to
the nearest tree trunk, often a distance of several or many yards, and
start up it, instantly disappearing to the far side of it. The trees
climbed were usually small, two to eight inches in trunk diameter;
however, in the second growth forest where the study was made, large
mature trees were relatively scarce. Having started up the tree trunk
and concealed itself on the side opposite from its pursuer, the skink
usually stopped one to five feet from the ground and waited quietly for
the danger to pass. A vine of Virginia creeper, poison ivy, grape or
moonseed, or a shrub such as gooseberry, providing screening foliage at
the base of the tree trunk, furnished the type of sheltered situation
that the skink was most likely to choose as a stopping place. The most
effective technique for catching the lizard was to move slowly around
the tree trunk at a distance of at least 20 or 30 feet and look for the
lizard clinging to it. Having located the lizard, the collector might
take careful note of its position, then return to the opposite side of
the tree and approach, unseen, to close range to make a sudden grab
around the trunk. This ruse often succeeded; more frequently it failed,
because of the lizard's adroitness in dodging, or failure of the
collector to gauge its position accurately, or a slight shifting of its
position between the time it was seen and the time when an attempt was
made to catch it. The response of the lizard to the unsuccessful attempt
to seize it depended on whether or not it was touched, and in which
direction it was driven. It might drop to the ground and burrow into
leaf litter or dash away to other shelter, or it might stay on the tree
trunk and spiral rapidly upward out of reach. Because of the
squirrel-like tendency to keep the tree trunk between it and the
pursuer, the skink usually could be relocated only after some
maneuvering. Having climbed the tree trunk to the bases of the main
branches, the skink usually showed little inclination to move out along
them but tended to hide in the crotches or to spiral back down the
trunk. Often a long stick or pole was used effectively to drive a skink
back down the trunk by touching or pushing it on the upper side. A skink
maneuvered to the lower part of the tree trunk was never loath to leave
it in a dash for other shelter, which might be another tree trunk
nearby. In moving downward or horizontally on a tree trunk or limb, a
skink allows its heavy tail to bend downward from its own weight. The
tail probably handicaps the lizard's climbing to some extent, and those
with short regenerated tails have an advantage.
The following extracts from my field notes are selected as typical
illustrations of the climbing habit as a response to danger.
September 15, 1948. A skink darted across the trail in front of me, to a
tree 18 inches in diameter and climbed to a height of five feet where it
stopped. Each time that I moved to approach and examine it, the skink
was disturbed, and darted jerkily higher up the trunk until it was well
out of reach at a height of about ten feet.
May 2, 1949. Seeing an adult male skink lying in the open, I attempted
to stalk it, but it became alarmed, ran to a shagbark hickory about six
inches in diameter, and soon had climbed to a height of 25 feet.
June 4, 1949. Juvenile, basking a few inches above ground on trunk of an
elm ten inches in diameter, took alarm at my approach, and climbed
rapidly out of reach, where it concealed itself in thick foliage.
June 22, 1949. Movement two feet above ground on an elm sapling
attracted my attention; an adult male and a juvenal skink were clinging
to the trunk only a few inches apart, and neither moved as I approached
and examined them from a distance of less than three feet. The
concealment afforded by numerous short twigs with thick foliage
apparently caused them to feel secure.