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 frequentedby 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 inTable 16but 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.
Spiders, harvestmen, and snails were well represented in both samples. In the bridge sample, salticids (especiallyPhidippus audax), grouse locusts, and the snailGastrocoptawere more numerous. In the rock pile sample lycosids, and especially ceuthophilid crickets were more abundant. The ceuthophilids were notablynumerous 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 femaleTheridionfrom 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° 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.
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.
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.
Like other members of the family Scincidae,Eumeces fasciatustends 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 genusEumeces, 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 areonly 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 threemonths 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 ofE. fasciatushave 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 oflaticepsandinexpectatus.” 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 tomove 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[132]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.September 21, 1949. A juvenile was noticed climbing eight feet above the ground on a locust trunk. As I approached the skink continued upward to a height of approximately 15 feet above the ground where it disappeared around the trunk and could not be relocated.July 7, 1950. A nearly grown juvenile ran to an elm sapling four inches in diameter, and climbed up out of reach. When the skink reached the main crotch, it turned facing downward alertly. By reaching up with a long stick and poking it on the hindquarters, I succeeded several times in chasing it part way down the trunk, but each time it ran back up to the crotch and returned to the same position.July 26, 1950. A hatchling uncovered beneath a flat rock ran to a nearby oak tree about four inches in diameter and climbed to a height of five feet before it was caught. An adult female seen foraging in the open ran to a dead shrub and climbed one of the stems, inclined at an angle of about 45°. Ascending this stem she was unable to get more than three feet above the ground, and was easily captured. Another adult female seen foraging in the open ran to an oak about three inches in diameter, climbed rapidly to a height a little more than a foot above the ground, and concealed herself under the stem of a poison ivy vine twined about the tree trunk.July 27, 1951. A female brooding her eggs dashed out of the nest when the flat rock covering it was lifted, ran 15 feet to a hickory sapling and climbed it.May 1, 1952. An adult male found beneath a rock ran to a small tree ten feet away, climbed up on the opposite side, and stopped about a foot above the ground. My first attempt to seize it failed and it ran around the trunk and stopped at a height of four feet. The next try was likewise unsuccessful, and the skink dropped to the ground and burrowed into leaf litter.May 15, 1952. An adult male startled as it basked in a patch of sunlight in thick woods, dashed 25 feet without stopping, to an osage orange tree and disappeared behind the base of the trunk. Moving to the far side of the tree I located the skink clinging to the trunk two feet above the ground. My attempt to catch it failed and it spiralled up the trunk to a height of ten feet. When I poked at it with a stick, it crouched close to the trunk allowing the stick almost to touch it, then it spiralled down the trunk and could not be relocated.June 23, 1952. When I struck the trunk of a partly dead ailanthus tree with a brush knife to determine whether it was hollow, a juvenile darted out of a cavity five feet above the ground, ran farther up the trunk, and disappeared into another small hole. An adult male was seen running across the vertical wall of a building, clinging to the rough asphalt siding. When it was alarmed it ran to a crevice and hid.
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[132]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.
September 21, 1949. A juvenile was noticed climbing eight feet above the ground on a locust trunk. As I approached the skink continued upward to a height of approximately 15 feet above the ground where it disappeared around the trunk and could not be relocated.
July 7, 1950. A nearly grown juvenile ran to an elm sapling four inches in diameter, and climbed up out of reach. When the skink reached the main crotch, it turned facing downward alertly. By reaching up with a long stick and poking it on the hindquarters, I succeeded several times in chasing it part way down the trunk, but each time it ran back up to the crotch and returned to the same position.
July 26, 1950. A hatchling uncovered beneath a flat rock ran to a nearby oak tree about four inches in diameter and climbed to a height of five feet before it was caught. An adult female seen foraging in the open ran to a dead shrub and climbed one of the stems, inclined at an angle of about 45°. Ascending this stem she was unable to get more than three feet above the ground, and was easily captured. Another adult female seen foraging in the open ran to an oak about three inches in diameter, climbed rapidly to a height a little more than a foot above the ground, and concealed herself under the stem of a poison ivy vine twined about the tree trunk.
July 27, 1951. A female brooding her eggs dashed out of the nest when the flat rock covering it was lifted, ran 15 feet to a hickory sapling and climbed it.
May 1, 1952. An adult male found beneath a rock ran to a small tree ten feet away, climbed up on the opposite side, and stopped about a foot above the ground. My first attempt to seize it failed and it ran around the trunk and stopped at a height of four feet. The next try was likewise unsuccessful, and the skink dropped to the ground and burrowed into leaf litter.
May 15, 1952. An adult male startled as it basked in a patch of sunlight in thick woods, dashed 25 feet without stopping, to an osage orange tree and disappeared behind the base of the trunk. Moving to the far side of the tree I located the skink clinging to the trunk two feet above the ground. My attempt to catch it failed and it spiralled up the trunk to a height of ten feet. When I poked at it with a stick, it crouched close to the trunk allowing the stick almost to touch it, then it spiralled down the trunk and could not be relocated.
June 23, 1952. When I struck the trunk of a partly dead ailanthus tree with a brush knife to determine whether it was hollow, a juvenile darted out of a cavity five feet above the ground, ran farther up the trunk, and disappeared into another small hole. An adult male was seen running across the vertical wall of a building, clinging to the rough asphalt siding. When it was alarmed it ran to a crevice and hid.
A more unusual escape-reaction was observed on May 25, 1952, at Tonganoxie State Lake, by Sydney Anderson, who recorded that a skink, alarmed by him at the edge of the water dived and hid among submerged rocks. Similarly, Boyer and Heinze (1934:194) record of this species, in Jefferson County, Missouri: "When pursuedthey do not hesitate to take to the water and are very agile swimmers over short distances at least." Parker (1948:25) wrote that in western Tennesseefasciatussometimes showed a preference for habitat in the vicinity of water, and, if other concealment was not available, it would usually take refuge in the water.
Little is known concerning the kinds of predators that destroy five-lined skinks, or their importance in its ecology. In studies of the food habits of various predatory birds and mammals, workers often have been interested chiefly in items of direct economic bearing, and have tended to lump as “lizard” or “reptile” material that might have includedEumeces fasciatus. I have been able to find only a few specific references to predation on it. Nevertheless many kinds of predators probably utilize it as food, at least occasionally. Owls probably seldom have opportunity to prey on these skinks, which are not known to be active after dark. Nestling broad-winged hawks observed in 1954 were found to have eaten an adult and a subadult five-lined skink on June 13 and June 23. The Cooper’s hawk and red-shouldered hawk also are probable predators as both are known to feed upon small reptiles. Mammalian predators which might be expected to take skinks occasionally include the red fox, gray fox, bobcat, mink, weasels, skunks, opossum, armadillo, moles, and shrews. Snakes, especially those of the generaElaphe,Lampropeltis,Cemophora,MicrurusandAncistrodon, may include some of the chief predators on the skink. Certain larger lizards also may prey upon it.
Of these several potential predators, only the opossum, armadillo, and snakes (Elaphe obsoleta,E. guttata,Lampropeltis triangulum,L. calligaster,L. getulus, andAncistrodon contortrix), Sonoran skink and the greater five-lined skink (in confinement) have actually been recorded as preying onEumeces fasciatusbut circumstantial evidence has been obtained for the mole (Scalopus aquaticus) and short-tailed shrew (Blarina brevicauda). The short-tailed shrew may be one of the major predators on the skink. This shrew prefers the same habitats and occurs throughout the skink’s extensive range. Like the skink, it is a characteristic inhabitant of the hardwood forests of the eastern United States, but its range extends farther north and west. A high proportion of the skinks examined had scars, usually on the sides or dorsal surface of the body, or of the tail near its base—wounds which must have been made by a small, sharp-toothed animal. For example, in May1951, eighteen per cent of 155 skinks captured on the study areas had such scars. The incidence seemed to vary according to age and possibly sex; the scars were present in 22.9 per cent of the adult males, 25.5 per cent of the adult females, and only 9.8 per cent of the yearlings (these three groups being represented by approximately equal numbers in the sample). As the scars are more or less permanent, adults could be expected to show a much higher incidence than young. Females, being inclined to stay in their nest burrows and defend them against small predators, may receive more wounds than the males, which are quicker to escape. None of the invertebrates present on the study area is sufficiently large or powerful to inflict such wounds, and none of the birds, reptiles, or amphibians has a dentition capable of producing them. The wood mouse (Peromyscus leucopus) is the most abundant small mammal in the skink’s habitat; other rodents present in relatively small numbers include the prairie vole (Microtus ochrogaster), harvest mouse (Reithrodontomys megalotis) and pine vole (Microtus pinetorum). Both voles and harvest mice have been known to kill skinks caught in the same traps with them, but individuals experimentally placed with skinks in captivity have failed to molest them and it seems likely that the attacks in traps were motivated by extreme hunger or self defense. The irregular scars from lacerated wounds characteristic of the skinks bear little similarity to rodent bites, in which the long, sharp-edge incisors make slit-like punctures. Other small mammals abundant in the places where skinks were studied were the insectivores: the common mole, short-tailed shrew, and least shrew (Cryptotis parva).
On one occasion when a large five-lined skink was put in a terrarium with a recently captured short-tailed shrew, each displayed strong aversion for the other. The skink crouched, attempting to conceal itself in the end of the terrarium farthest from the shrew, and resisted efforts to drive it toward the shrew. In exploring the terrarium the shrew several times sensed the skink’s presence, and then scampered away in frantic haste. The skink also rushed away several times when the shrew came close enough to disturb it. Three days later, when the shrew had become accustomed to the terrarium, the test was repeated, with different results. The shrew, having finished the food left for it, was noticed moving about the terrarium, sniffing and testing objects with its tactile snout, obviously hungry and searching for more food. The skink was then dropped near it. In a few seconds the shrew sensed the skink’s presence and pounced upon it, and bit hard on its back. The skinkreacted with a violent flexure of its body which caused the shrew to release it instantly, and both rushed away in opposite directions. After a few seconds the shrew located the skink again, and moved up to it with little hesitation but with nervous alert sniffing, and delivered another quick bite after which the two separated as before, the skink showing signs of injury. Soon the shrew attacked a third time, and bit the skink’s tail severing it near the base. As the skink rushed away, the detached tail performed lively squirming movements, but the shrew seized it, held it down, and began to eat the exposed flesh on the broken end as the tail writhed. After rapid nibbling it would drop the tail, and leaving it temporarily would explore the terrarium. Several times on these trips it encountered the skink and renewed its attack. As death of the skink seemed imminent, it was then removed, and it survived with no apparent ill effects. The wounds inflicted by the shrew bore close resemblance to those noticed on skinks in the wild. It seemed almost certain thatBlarinahad inflicted most of these wounds or all of them. On subsequent occasions several other captive shrews that were tested, quickly killed and ate skinks that were introduced into their containers. The least shrew,Cryptotis, likewise occurred in all situations where skinks were taken, and in some localities was more abundant than the largerBlarina. Bites inflicted by these two kinds of shrews might be indistinguishable, but because of its larger size,Blarinawould seem by far the more formidable enemy.
Reynolds (1945:367) foundE. fasciatusto be the most frequent reptile in a collection of opossum scats from Missouri, with two occurrences in 100 fall scats and ten occurrences in 100 spring scats. Sandidge (1953:98 and 101) recorded one of these skinks among numerous other items identified from stomach contents of sixty-six opossums. Probably the opossum is a frequent predator on this skink. Although no specific instances were obtained on the area of the study, flat rocks a few inches in diameter frequently have been found flipped over, larger ones and those solidly anchored in the ground have been found partly undermined by opossums scratching away the loose dirt at their edges. The rocks found disturbed by opossums were typical of those used as shelter by the skink. On many occasions wire funnel traps set for skinks and other reptiles along hilltop rock ledges were found to have been disturbed, either shifted in position or with their rock shelters removed, or rolled downhill or broken open. Similarly, heavy flat rocks used to cover pitfalls, to protect the small animals falling into them from predators, often were foundto have been shifted somewhat, or completely removed. When such raids became frequent and troublesome, steel traps were set beside the reptile traps to discourage the raiders or catch them and determine their identity. On several occasions opossums were caught and somewhat less frequently, spotted skunks (Spilogale interrupta). These skunks probably prey regularly on lizards including the five-lined skink. However no definite records were obtained. Crabb (1941:356-358) in his food habits study of the spotted skunk in southeastern Iowa, did not record this or any other species of reptile among the items identified in 834 scats. On the Reservation both opossums and skunks were, in many instances, attracted to the reptile traps by the insects and other arthropods in them, rather than by lizards. The striped skunk (Mephitis mephitis) is another of the predators which probably feeds upon the five-lined skink occasionally on this area.
In the contents of 103 armadillo stomachs collected in west-central Louisiana, in 1947 and 1948 I found the broken tail of oneEumeces fasciatus. The lizard itself evidently had escaped (Fitch, 1949a:88). Many clutches of lizard eggs were found in the contents of the armadillo stomachs and some of these probably were eggs ofEumeces, which are similar to those of other small lizards in the same region (Anolis carolinensis,Sceloporus undulatus) in size, shape, and color.
Among 217 identified prey items from stomachs and scats of Sonoran skinks (Eumeces obsoletus) from northeastern Kansas were remains of three hatchling five-lined skinks. Taylor (1953b:212) recorded that aEumeces laticepsshipped from Arkansas to Kansas ate anE. fasciatusthat was with it in the container. Several authors have recorded predation onEumeces fasciatusby snakes of various kinds in captivity. Conant (1951:211) recorded that one was eaten by a blacksnake (Coluber constrictor) placed in the collecting sack with it. Anderson (1942:211 and 216) recorded that a king snake (Lampropeltis getulus holbrooki) and a young copperhead (Ancistrodon contortrix) each fed upon them. Hurter (1911:184) recorded that a milk snake,Lampropeltis triangulum syspila, placed in a bucket with aEumeces fasciatuswas found swallowing it a short time later and its tail had been broken off.
Ruthven (1911:268) mentioned that stomachs of milk snakes,L. t. triangulum, collected in Michigan contained remains of five-lined skinks. Ditmars (1907:352) wrote that stomachs of severalL. t. elapsoidescontainedEumeces, and Wright and Bishop (1915:167) wrote of the same kind of king snake in the Okefinokee Swampregion: “It feeds on ground lizards, skinks, swifts, and other snakes and lizards.”
Mr. Richard B. Loomis is of the opinion that the five-lined skink is one of the chief food sources for the milk snake (L. t. syspila). Having kept many of these snakes in captivity and experimentally offered them different types of prey, he found that individuals inclined to feed would avidly seize and eat skinks and young mice, but other proffered prey, small adult rodents, snakes, or lizards other thanEumeceswere either rejected or were taken with some hesitation. These milk snakes have habitat preferences similar to the skink, which would seem to be one of the most available food sources. Loomis recorded in his field notes that a juvenal blotched king snake (L. calligaster) 310 mm. in total length, taken on April 8, 1950, seven miles southwest of Tulsa, Oklahoma, had eaten a large adultE. fasciatus. Another juvenal blotched king snake that he found under a flat rock near Sunflower, Johnson County, Kansas, regurgitated an adult five-lined skink. Loomis also recorded a juvenal rat snake (Elaphe guttata emoryi) and a juvenal pilot black snake (E. obsoleta) each feeding on individuals ofEumeces fasciatusin captivity. Uhler, Cottam and Clarke (1939:622) in a study of the contents of the alimentary tracts of 893 snakes of 18 species, from the George Washington National Forest, Virginia, found among the prey items only one skink (species undetermined but most probablyE. fasciatus). It had been eaten by one of the two corn snakes (Elaphe guttata) that were examined in the study.
On June 11, 1950, in Skink Woods, a young copperhead 335 mm. in snout-vent length and weighing 27.6 grams, had a gravid female skink in its stomach. Another young copperhead (335 mm., 36.1 grams) trapped near Rat Woods on August 28, 1953, had in its stomach a bob-tailed adult five-lined skink. Many copperheads collected on the Reservation were kept in captivity for short periods, and from them a total of 44 scats were obtained, each scat containing the remains of one or more prey animals eaten in the wild. Of this total, five scats contained remains ofEumeces fasciatus, which was one of the more frequent items, although small mammals collectively made up the bulk of the scat contents.
Skinks, like many other lizards, are likely to be infested with parasites. Little attention was devoted to the endoparasites in the present study, but they were noted from time to time. On several occasions small nematodes and flukes were seen in feces voided bylizards which were handled. Small white cysts were seen in the body cavities of several that were dissected.
Harwood (1932:65) examined for endoparasites nineE. fasciatusalong with many other reptiles and amphibians collected near Houston, Texas. Most of them were infested and five kinds of helminths were identified. Two of the skinks were infested withOswaldocruzia pipiens, a spirurid nematode that was also present in various other lizards, snakes, toads and frogs from the same region; four hadComocercoides dukae, an oxyurid nematode also present in various lizards, snakes, turtles, and frogs; one had in its intestineOochoristica eumecis, named as a new species by Harwood, and found only inEumeces; one containedCysticercussp. in its body cavity, present in great abundance as white globular structures .6 mm. in diameter (Harwood states that possibly these were larvae ofOochoristica). One skink containedMesocoelium americanum, a dicrocoelid trematode which was found also in the brown skink (Scincella laterale) and DeKay’s snake (Storeria dekayi).
The ectoparasites of these skinks consist mainly of chiggers. Wharton (1952:135) lists three species;Trombicula alfreddugesi,T. splendens, andT. gurneyi. The first species is the common pest chigger of humans and domestic animals in the United States, and south through tropical America. Wharton lists 136 known hosts which are fairly evenly divided among mammals, birds and reptiles; he lists four kinds of frogs and toads.Trombicula splendensis a similar and closely related species which has been recorded from thirty-eight vertebrate hosts including mammals, birds, reptiles, and a tree-toad.Trombicula gurneyibelongs to a separate subgenus and it was originally recorded fromEumeces fasciatuswhich seems to be one of the principal hosts.
Two of these mites,T. alfreddugesiandT. gurneyi, were on skinks collected on the Reservation, and nearby areas. A four year study of the chiggers in this general region by Loomis (MS), Wolfenbarger (1953) and Kardos (MS) has clarified the ecological relationships of the several kinds of chiggers present, including their local distribution with respect to vegetation, soil type, moisture and temperature, host preferences, and seasonal occurrence. At the quarry, Rat Woods and the pond rock pile, the chigger population consisted chiefly ofT. alfreddugesi, while at Skink WoodsT. gurneyiwas also abundant. In some local situations where they are among the most abundant of vertebrates the skinks probably are importantas hosts ofT. gurneyi. An individual skink may have dozens of chiggers on it at one time but usually there are fewer.
There are several favorable sites of attachment. The most favored site is in the axilla. There the scales are minute and granular with exposed areas of thin and tender skin, and the chiggers are well protected from dessication and are not likely to be rubbed off as the skink moves about. Other favorite sites of attachment are: about the insertion of the hind limb, about the cloacal opening, on the eyelids and on the toes. Only occasionally are chiggers found attached on the dorsal surface. When attached in protected spots in the tender skin of the axilla or groin, they are often in dense clusters of a dozen or more. Damage to the skin resulting from the attachment of the first chiggers renders conditions more favorable for the attachment of others. At Rat Ledge and at the quarry, many of the larger Sonoran skinks (Eumeces obsoletus) were captured, and individuals were far more heavily infested than wereE. fasciatusfrom the same places. A single Sonoran skink might be found to have hundreds of chiggers, widely distributed over its body with concentrations at the axillae, groins, lateral neck region, and any injured spots where the protective armor of scales was broken. The reasons for the greater susceptibility ofE. obsoletusare not entirely clear. It is a larger, less active species with coarser scalation, and is more subterranean in its habits.
The chiggers that attach to skinks seem to occasion but little discomfort. There is no local swelling and inflammation such as occurs in humans. The infestations observed in five-lined skinks were not sufficiently severe to cause debilitation or any noticeable symptoms. There is, however, a possibility that chiggers are vectors of microorganisms causing diseases in reptiles, just as they are for certain mammals (including humans) in some parts of the world.
Bishopp and Trembley (1935:42) record a single kind of tick,Ixodes ricinus scapularisSay, the black-legged tick, as parasitic in its immature stages onEumeces fasciatus. This tick, however, has been recorded principally from mammals, of which many kinds serve as hosts for its larval, nymphal, and adult stages.
Population structure obviously differs from place to place and from time to time. Because of the differences in secretiveness and elusiveness between young and adults and between males and females, true sex ratios and age ratios are obscured. In the period ofweeks between the emergence from hibernation and the onset of the breeding season, these skinks tend to be less secretive than at other times, and secondary sexual and age differences in behavior are minimized. A sample at this season should be more representative of the true population composition than samples taken at other times of year. In a sample of 308 skinks available for the month of April, including the collections made on the Reservation and on nearby areas, in 1949, 1950, 1951, and 1952, 36.7 per cent were adult males, 28.3 per cent were adult females, and 35.0 per cent were young. That these figures cannot, however, be accepted as an accurate indication of the population composition is shown by the data from the areas where intensive population studies were made. Data are most complete from Skink Woods. For 292 adults taken there over a four year period, the sex ratio was 100:122.6. On this area after the first year of study a substantial proportion of the individuals recorded were repeaters from one year to the next, and in some cases for three or even four successive years. Many could be definitely assigned to a known age group. By analogy the majority of others could be tentatively assigned with some assurance on the basis of measurements, and relatively few were of indeterminate status. By assigning each of these indeterminate individuals to one or another age group, on the basis of greatest probability, the approximate composition of the population could be determined. Of 611 adults, 55 per cent were “two-year olds” (in the season between their second and third hibernations, which was their first breeding season). The percentage was not significantly different in the two sexes.
On the average, a pair of adults produces somewhat more than nine eggs per year. From the time individuals of a brood start their development in the egg until they are breeding adults two years later, they undergo such drastic reduction in numbers that, on the average, approximately only one per brood survives. Most of the mortality probably occurs early, especially before hatching, also in the inexperienced hatchlings, and in the first hibernation. In spring, after emergence from hibernation, young are generally taken in smaller numbers than are adults. Their relative scarcity is only apparent, owing to greater secretiveness, and greater elusiveness when found. In spring, newly matured adults (age class about 21 months) may be taken in somewhat larger numbers than young (age class about 9 months). The latter obviously must be more numerous, in a stable population however, as the 21 month age class necessarily has sustained some loss since it was 9 months old.
Success of the annual brood varies greatly from year to year, depending on the weather and various other factors. In 1949 evidently conditions were near optimum; young hatched early and were especially numerous in late summer. In 1950 these young hatched in 1949 made up 40 per cent of the total catch (excluding hatchlings) in Skink Woods and were relatively more numerous than young of the corresponding age group in other years. In 1951, these young of the 1949 brood, grown to adults, made up 70 per cent of the breeding populations, as against 36 per cent for the corresponding class in 1950 and 58 per cent for the corresponding class in 1952.
Even after attainment of adulthood, any given age group evidently is subject to annual reduction amounting to at least half its numbers. Within six or seven years, at the most, the original numbers would be reduced to an insignificant percentage. At an age of four or five years individuals probably have attained their maximum size, with obscured pattern and changed proportions suggestive of advanced age. Occasional individuals possibly attain much greater age, but certainly few live more than five years. Like most small animals, the five-lined skink has a short life expectancy and a rapid population turnover. As compared with mammals of comparable sizes, the small rodents and insectivores that are this lizard’s community associates and are subject to many of the same hazards, the skink is notably successful, with a much longer life expectancy. For these small mammals the life span is seldom as long as a year. Most kinds of small birds likewise have a life expectancy less than that of the five-lined skink, although somewhat greater than that of small mammals.
The population density changes constantly, following an annual cycle with gradual reduction to its lowest ebb in late June or early July, then rapid increase to a high point a few weeks later when hatching of the single annual brood has been completed. In a normally successful breeding season the population is at least doubled, but reproductive success varies from year to year, as the population responds to weather conditions that are favorable or unfavorable, even where the environment remains fairly stable. In most places, however, local populations continue upward or downward trends for periods of years in response to successional changes which cause progressive improvement or deterioration of local habitats. Local populations are likely to be more or less isolated from others by areas where the habitat does not exist. Even in an areaof favorable habitat such as a wooded hillside of several acres, the population is not at all evenly distributed, but concentrations occur along rock outcrops, and about decaying logs, or stone piles. In intervening areas lacking such abundant shelter, and less productive of food, the population is sparse, or there may be no permanent residents.
In view of these traits, and the difficulty of obtaining a representative sample, no precise measurements of population density can be made. During the time required to secure a sample, the population undergoes change. At the pond rock pile, an area of approximately .05 acre, the skinks were found in remarkably high concentrations, 57 in 1949, 85 in 1950, 37 in 1951, and 51 in 1952. These numbers represent population densities of, respectively, 1120 per acre, 1960 per acre, 746 per acre, and 1000 per acre. No such concentrations were found elsewhere, and probably do not occur in natural habitat. The Skink Woods study area of 21⁄4acres is typical of favorable habitat in the region of the study, and the numbers taken there are more significant. For 1949 the 74 skinks recorded comprise an incomplete sample, and the population density of 33 per acre represented is certainly somewhat too low. For other years the following population densities (exclusive of hatchlings) are indicated: 1950, 92 per acre; 1951, 61 per acre; 1952, 49 per acre. These figures are only approximate, of course, and it is difficult to judge how accurately they reflect the true numbers. Even the most intensive collecting may be insufficient to obtain every individual on a small area. Within each season there are shifts of range by some individuals, off the study area and corresponding shifts onto it by others, so that the numbers caught in the course of an entire season are somewhat too high. The individuals taken on the study area may regularly range beyond its boundaries to some extent, so that the seeming population density is somewhat too high. Actually this was probably a minor source of error for the Skink Woods study area, as nearly half its perimeter was bordered by an open field uninhabitable for the skinks, and the remaining perimeter adjoined areas much less favorable than the central portion.
Census of the population of the study area by a ratio such as the “Lincoln Index” used in game management studies was scarcely practicable because of the changing seasonal habits distorting the recorded ratios of the sexes and of age groups somewhat differently at different stages of the season. These changing ratios tend to produce an erroneously high population figure, unless separate computations are made from the data for adult males, adult females, andyoung. Census figures obtained by this method were erratic but seemed to bear out in a general way, the population figures based on total numbers of individuals taken.
In favorable habitat where they occur in high populations of 50 to 100 per acre in spring, these lizards must attain a biomass of a pound or more per acre. Biomass in a population probably fluctuates but little during the course of the annual cycle, even though the number of individuals changes greatly. The steady elimination of individuals through various mortality factors, is compensated for by rapid growth of the young.
Five-lined skinks were studied for four consecutive years in four small areas, totalling approximately ten acres, on the University of Kansas Natural History Reservation, Douglas County, Kansas. The information gained from intensive study on these areas has been supplemented by data from skinks collected elsewhere in northeastern Kansas, and from an extensive literature pertaining to this species.
The genusEumeces, to which the common five-lined skink belongs, has more than 50 species, occurring throughout Central America, North America to the latitude of southern Canada, and, in the Old World, across southern Asia and North Africa. Within the genus, the five-lined skinks, comprising a dozen species, form a natural group of closely related forms. In this “fasciatusgroup” nine of the species occur in the Orient, Japan and neighboring islands and the adjacent mainland. The remaining three, includingE. fasciatus, occur in the eastern United States. Specific differences are to be found in details of pattern, scalation, and size, and, in some instances, they were long unrecognized.E. fasciatuscoincides closely in its distribution with the Deciduous Forest Biome of southeastern North America. An early Tertiary deciduous forest in Alaska and probably in the Bering Strait area, evidently growing in a humid, mild-temperate climate, included genera of plants that are now most characteristic of southeastern North America along with other kinds now characteristic of forest remnants in southeastern Asia, and still others characteristic of the western United States. Thefasciatusgroup seemingly dispersed from a northern center that may have coincided with the early Tertiary deciduous forest of Alaska.
Eumeces laticepsalmost coincides in distribution withE. fasciatus, but does not occur quite so far north, and unlikefasciatusit occursthroughout Florida. Young are similar in appearance butlaticepsis a larger, more powerful species, notably arboreal in its habits.E. inexpectatusmuch more closely resemblesfasciatus, and ecological divergence is slight. It is characteristic of hot and dry rocky areas in open woods, and is more southern in distribution, although there is extensive overlap withfasciatusandinexpectatusshares nearly all of its range withlaticeps.
Eumeces fasciatusis most abundant in well-drained, open, rocky situations within its forest habitat. It is scarce or absent in bottomland forest that is subject to flooding and requires a forest with openings in the leaf canopy so that sunshine patches for basking are available. In northeastern Kansas, at least, woodlands that are browsed by livestock, and have scanty undergrowth, provide better habitat than those that are protected.E. fasciatusis likely to be most abundant in cutover woodland, and may reach greatest numbers in artificial situations, such as old rock piles, or the vicinity of deserted sawmills. In the north, the species is increasingly confined to open situations, while in the south it may inhabit heavily wooded areas. An abundant supply of moisture is a necessity and the species is limited to a climate of high humidity. Dew normally supplies the source of drinking water, without which the skinks rapidly become emaciated and die. Optimum body temperature was determined to be near 34°C., from a series of temperature readings taken both under natural conditions and in confinement under conditions permitting behavioral thermoregulation. By thermoregulatory behavior, active skinks in the wild tend to maintain their body temperatures near this level over a wide range of environmental temperatures. They can tolerate body temperatures only a few degrees higher, but, within a range of several degrees below 34°C., efficiency is little impaired and incentive to make readjustment is slight. At progressively lower temperatures skinks become slower and less efficient. They are, however, capable of copulation at temperatures down to 21°C, and of feeding at 16°C. At 10°C. they are slow and clumsy, barely capable of normal locomotion. At temperatures near freezing they are torpid; they can survive temperatures a little below freezing, but cannot survive being frozen solid. More than half the year is spent in hibernation in northeastern Kansas. Weight loss is slight during hibernation.
Normally the skinks emerge from hibernation in early April in northeastern Kansas, several weeks earlier in the southern states and correspondingly later in the northern part of the range. Maximum activity occurs in the period of weeks following emergence; interruptedfrom time to time by cold weather which necessitates return to torpidity. After approximately three weeks of activity the adults attain breeding condition. Breeding males acquire a salmon red suffusion of the head region. They become pugnacious and fight on sight. Fighting does not involve territorial defense. In confinement males may mutilate or kill each other. In their search for females, and fighting, the breeding males are so much more active and conspicuous than they are at other times of year that published descriptions usually refer to males as red-headed, with no cognizance of the fact that this condition exists for only a few weeks in the annual cycle. Old adult males lose the striped pattern and blue color of the tail of the young, and are golden brown, usually a little darker on the sides. Males find females by a combination of sight and scent. Sexual relations are promiscuous, and there is but little courtship behavior. The male pursues the female and grasps in his jaws loose skin at or behind her shoulder region, and maintains this hold during copulation which lasts about five minutes. Within a few days after insemination, usually in early May, females become actively hostile to males. In late May or early June the gravid females become unusually secretive and excavate nest burrows in damp soil under flat rocks, or in rotten wood of decaying logs and stumps. The single annual clutch of eggs is laid in June. The average clutch is somewhat more than nine eggs, with larger and older females slightly exceeding younger and smaller females in average productivity. The female remains in the nest burrow with her clutch most of the time, from laying until after hatching. She alters the nest burrow, dampens it in time of drought, keeps the cavity from being filled with loose soil, prevents the eggs from adhering to the sides or floor of the cavity, and she may repulse certain small predators capable of destroying the eggs if they were left undefended. When they are laid, the eggs are approximately 11 × 71⁄2mm. and weigh .4 grams or a little less. By hatching time they have enlarged to 15 × 11 mm. and each weighs about a gram. Recorded incubation periods vary from 27 days to 47 days; development of the embryo is slowed at low temperatures, and eggs experimentally kept in a refrigerator at 11° to 12°C. for periods of days hatched later than others of the same clutch that developed under normal conditions, indicating that development was almost halted in the eggs kept at such low temperatures. Eggs are, however, tolerant of a wide range of temperature, and can develop in nearly dry soil, or can survive partial submersion in water for at least two days. Under weather conditions prevailing in 1951, incubation periods of about six weeks were recorded. Incubation may be shortenedby retention of ova in the oviducts in early stages of embryonic development. Hatching may occur from the first week of July to mid-August, but in any one year most clutches hatch within two weeks of each other. Hatching of eggs in a clutch extends over a day or two. The hatchling gradually becoming active inside the egg, slits the leathery shell with its egg tooth, and spends several hours in the early stages of emergence. After resting with head and shoulders protruding, becoming adjusted to the outside environment and gaining strength, it lunges from the egg. For a day or two after hatching, the young remains in the nest, being slow and feeble, and handicapped in its movements by the protruding belly distended by the yolk mass. The female usually remains in the nest cavity for a day or two after the eggs hatch, showing affinity for the young by curling around them protectively. Family ties are broken as soon as the young leave the nest, and they do not return. Hatchlings average a little less than an inch in snout-vent length, and have a sharply defined five-lined pattern on a black ground color, and vivid blue tail. Hatchlings make rapid growth in late summer, and by the time of their retirement into hibernation, the more successful may have doubled in length, and may have increased their original weight, of approximately .3 or .4 grams, more than eight-fold. After emergence from their first hibernation the young continue their rapid growth. When they are a year old, some of them are as large as small adults. However, they can usually be distinguished from adults by the more sharply defined pattern. These grown young retain the hatchling pattern but the contrast between stripes and ground color, and between body and tail is not quite so sharp. Especially in those with regenerated tails, the vivid blue of the hatchling’s tail has become much dulled. By the time they retire to their second hibernation, the young have mostly grown to small adult size. A small percentage are retarded in their growth and fail to mature. Upon emergence from their second hibernation, the grown young mature sexually and participate in the annual breeding season, in early May, and they may comprise the majority of breeding adults. The ratio of new adults to old adults however varies from year to year depending on the varying fortunes of successive annual broods. The new adults overlap older ones in size, but are usually distinguishable on the basis of their coloration, as they retain the striped body pattern (dulled, especially on the head) and with distinctly blue color on the tail. In skinks that are three years old or more, the dorsal stripes have become obscured and partly blended with the ground color, which becomes progressively paler with advancing age. Metamorphosis is most complete in oldmales, which retain no trace of the stripes or of the blue color on the tail. Old females usually retain the dark lateral area, and the tail is usually bluish gray, with a blue scale remaining here and there if the tail has not been regenerated.
Most individuals lose their original tails, however. By the time the young are approximately two months old, about half have had their tails broken, and by the time they are a year old and have grown to small adult size, three-fourths have regenerated tails. Some individuals may have had their tails broken and regenerated many times. Tails regenerate rapidly and most of the growth is made within the first few weeks. The regenerated tail is not so long as the original lost portion.
Individuals tend to stay within small areas which are their regular home ranges. These ranges are only a fraction of an acre in extent, but vary considerably in size and shape according to the individual and the situation. Home ranges of approximately 90-foot diameter for adult males and young, and a little more than 30-foot diameter for adult females are indicated. A home range generally centers about some environmental feature providing shelter and food, such as a log, hollow tree, or rock outcrop. Activity tends to be concentrated in the central part of the home range. An individual may continue to occupy the same home range throughout its lifetime, or it may gradually alter its range, shifting by slow stages into a new area. Some individuals seem to “get lost” or voluntarily shift, and settle in a new area which may be hundreds of feet removed from the original range. Shifts are most likely to occur after emergence from hibernation, when the lizard finds its habitat somewhat altered. Individuals released in areas strange to them settled down and established new home ranges, either immediately or after brief wandering.
The five-lined skink is a predator, occasionally taking small vertebrates (lizards and possibly newborn mice) but depending for most of its food on invertebrates. Of these it takes a wide variety. Spiders are the mainstay of the diet, and various salticids and lycosids are the kinds most frequently preyed upon. Phalangids are also eaten. Of insects, orthopterans (including roaches, ceuthophilid and gryllid crickets, grouse locusts, and small grasshoppers) are most important in the food. Larvae of moths and both larvae and adults of beetles are also taken in quantity. Small snails make up an important part of the diet, and the skinks often eat their own sloughed skins. Less frequently taken food items include certain large ants, centipedes, moths, and miscellaneous insects. Rarely the adult skinks may even eat eggs or young of their own species.Prey is found by sight and scent, and consists of almost any small animals within a certain size range (small enough to be swallowed entire, but large enough to make up a substantial part of a meal) of types which are not too heavily armored, lack noxious defensive secretions, and live on or in the ground or decaying wood. They are ordinarily crushed in the jaws or battered against the ground, and then swallowed entire.
Natural enemies of the five-lined skink certainly include the broad-winged hawk and probably other kinds of hawks and also include various predatory mammals such as the opossum, armadillo, skunks, moles and shrews; snakes (the copperhead, milk snake, king snake, corn snake, and probably others), the Sonoran skink and even the closely related but largerEumeces laticeps. On the Reservation, the short-tailed shrew was certainly the commonest, and probably by far the most important natural enemy. A high proportion of the skinks examined had scars resembling those inflicted by shrews experimentally confined with skinks in captivity. In time of danger escape reactions vary according to the type of enemy and the attending circumstances. Frequently an alarmed skink may escape into a hole or crevice, running directly to it from a distance of several yards. Under other circumstances a skink may burrow into ground litter of dry leaves and other debris, or may even dive and hide underwater. One of the commonest escape reactions is climbing tree trunks. It occurs even in gravid females that are slow and clumsy, being weighed down with eggs. Generally the skink stays on the main trunk of the tree, attempting to conceal itself by utilizing the screening vegetation that is available. In the young, especially, the bright blue tail seems to be used as a decoy, for it is carried, arched high and waved conspicuously as the lizard moves about. Rapid lashing movements of the conspicuous tail as the animal darts erratically for shelter may serve to confuse a pursuer, at least as to the direction that the skink has taken.
This skink is parasitized by various helminths, both cestodes and nematodes, which inhabit the digestive tract and body cavity. Some of these infest many kinds of amphibian and reptilian hosts, but others may be confined to the five-lined skink. Their life cycles, and effect upon the host are not well known. Ectoparasites consist principally of chiggers. Three kinds have been recorded on the skinks;Trombicula alfreddugesi,T. splendens, andT. gurneyi. The first two are common pest chiggers which attack humans as well as a wide variety of other mammalian, avian and reptilian hosts.T. gurneyiis a less common species found mainly onEumeces fasciatusand confined to its woodland habitat.