Henry S. Fitch

“ 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. ”

“ In contrast to the delayed development of those that have failed to attain maturity at an age of two years, is the accelerated development of those that have already more than doubled in length before the first hibernation, and continue to grow rapidly after emergence. By late spring they are already approaching adult size, perhaps even before laying has occurred, and while breeding is still in progress. It is certain that in northeastern Kansas there is no breeding by such accelerated individuals approaching adult size at an age of nine or ten months. ”

“ 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 [10] and regenerated new tails. ”

“ Home ranges approximately 90 feet across for adult males and young, and a little more than 30 feet across for females are indicated. Actual area of a home range would amount to only a fraction of an acre—from about one-seventh to less than one-fiftieth. The dash of an alarmed skink to a place of refuge, though involving at most only a few seconds, may traverse a large part of its home range. Through long association the lizard is thoroughly familiar with the terrain, so that it can take full advantage of the peculiar features in escaping, hunting, traveling or resting. ”

“ In the breeding season the adult male directs the greater part of his activities to a search for females, and finds them by both sight and scent. Observations on searching males suggest that they trail females by scent to some extent, or at least detect their presence in the general vicinity by this means. Upon discovering a female, the male pursues her with vigor and determination unless the temperature is too low, or unless he is not at the height of breeding condition. ”

“ 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, [129] 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. ”

“ 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. ”

“ These individuals all had home ranges substantially larger than the average. It seems that in the five-lined skink there is no fixed size or shape for a home range, but that it varies within rather wide limits depending on age, sex, and perhaps individual peculiarities and on the presence and distribution of essential habitat features within the general area.
Most of the young that were recaptured had grown to subadult or adult size, so that the movements they made as young cannot be separated from those made when they were full grown or nearly so. ”

“ Particles of sharp rock from the nest cavity may adhere to the shell, and result in rupturing, perhaps at weak spots where prolonged contact with the soil has caused deterioration. The female tends to keep her eggs in a compact cluster, shifting their position frequently so that no part of an eggshell adheres to its surroundings long enough for rotting to occur, and most of the surface of each egg is exposed to the air.
Another important function of the brooding female seems to be that of altering the nest burrow and shifting the eggs so that the effects of unfavorable weather are minimized. ”

“ 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. ”

“ One adult female was partly exposed by scraping away loose soil into which she had burrowed. A mealworm was then dropped just in front of her head. She tested it several times with her tongue and then ate it without emerging, her movements being much less brisk than they normally are in feeding. Probably this approximates the threshhold temperature for feeding behavior. At 19.5°C. the several skinks in this terrarium were moving about in the open although they were not exposed to sunshine, and they accepted food avidly when it was offered, but were much slower than at optimum temperatures. ”

“ 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. ”

“ 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. ”

“ Eggs of other individuals of the species, and even the eggs of Eumeces laticeps were accepted as part of the brood. Any of the experimental females would quickly retrieve one of her eggs moved a short distance outside the nest cavity. Even if the whole clutch of eggs were scattered about, the female would, over a period of hours, gather the eggs and return them to the nest cavity. This movement of the eggs is accomplished by rolling or pushing them in a loop of the body or tail, or, less frequently, by grasping an egg in the jaws, lifting it, and gently placing it in a new position. ”

“ The activities gradually become more diffuse farther from the central part of the home range. In the five-lined skink, home ranges are unlikely to approximate the circular shape because they are molded with respect to environmental features that are not uniformly distributed. A rotting log, an old tree with decayed hollow base and nearby fallen slabs of bark and dead limbs, a rock outcrop with numerous deep holes and crevices, or a group of flat rocks in a forest glade fulfill requirements not met in the surrounding habitat with the result that home ranges are built around them. ”

“ The male suddenly thrusts his tail beneath that of the female. His hind leg then rests over the base of her tail and the right angle formed by the laterally projecting hind leg and the tail in each lizard aids to guide their hindquarters into position so that cloacal contact is established. Copulation then begins immediately. The male’s body may be bent in a semicircle, to one side of the female, or may be in an S-shaped loop, depending on whether or not the hemipenis employed is on the side opposite to that on which the female is grasped. ”

“ 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 of [140] weeks 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. ”

“ Captive skinks, in taking their food, seem to rely much less than some other lizards on movement of the prey as a means of detecting it. An active and hungry skink often failed to notice a spider or insect moving about on the opposite side of the terrarium a foot or more away. However, on many occasions, skinks moving about the terrarium and coming upon a motionless prey item have been seen to stop and examine it intently for several seconds, then grasp it, often in a tentative and hesitant manner, after testing it with the tongue. ”

“ 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. ”

“ Although no actual experiments were performed in the present study in connection with the courtship and mating behavior, accounts of some workers seem misleading. My own observations indicate that the capacity for sex discrimination in this particular kind of lizard, and probably in others, has been underrated. For example, it has been stated that the male rushes with open mouth at the neck of any other skink that happens to be around, and he identifies it as a male if it fights back, or as a female if it does not. ”

“ When a female was caught in her nest burrow, her temperature nearly always approximated that of the surrounding earth with which she was in contact. The temperature in each nest depends primarily upon its situation. When the immediate vicinity of the nest receives direct sunlight, the eggs are warmed without the aid of the female, but when there is no sunlight the temperature is much lower. In order to maintain an appreciably higher nest temperature the female would have to make frequent trips to spots perhaps several feet or several yards away to find sunlight. ”

“ 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. ”

“ 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. ”

“ The skink, however, is so secretive in habits that at any given time the individual is likely to be hiding and inactive, even when conditions are favorable for it to be in the open, and other individuals therefore can then wander onto its home range unopposed. Even when an individual is active, it lacks the ability to detect others, except within a radius which would encompass only a small fraction of [52] the entire home range. The senses are inadequate to inform one lizard of the presence of another until the two are only a few yards, or even a few inches apart. ”

“ 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. ”

“ Many kinds are most in evidence within a period of weeks after emergence from hibernation, which corresponds with the time of breeding and later they become much scarcer. In skinks of the genus Eumeces this tendency is perhaps even more pronounced than in most other kinds of reptiles. By midsummer or considerably earlier their period of greatest activity is passed, and in some kinds, adults, or individuals of any size can rarely be found in the latter half of the growing season, even by a skilled collector familiar with their habitats and habits. ”

“ In open woods home ranges tend to be larger or, at least, more elongate. Scattered distribution of such habitat features as flat rocks and outcrops, stumps, logs, and glades with patches of sunlight, may induce an individual to extend its activities over a more extensive area. For some of the adult males for which largest numbers of records are available, showing repeated movements back and forth within a definite area which seemingly constituted a home range, movements of 275 feet, 225 feet, 170 feet, 165 feet, 150 feet and 130 feet, respectively, have been recorded. ”

“ Local populations are likely to be more or less isolated from others by areas where the habitat does not exist. Even in an area [142] of 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. ”

“ 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 old [147] males, which retain no trace of the stripes or of the blue color on the tail. ”

“ 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. ”

“ Having once emerged from its hiding place a skink becomes more or less independent of the temperature of the air and substrate, as it is capable of thermoregulation through insolation. However, after a period of cooling and inactivity in dormancy, or merely resting for the night in temporary shelter, the skink is dependent on warmth from the air or substrate or both to become sufficiently activated so that it can emerge and take advantage of direct sunlight. ”

“ As in many other kinds of lizards, the tail in the five-lined skink serves as a reservoir for fat, which may be drawn upon for nutrition in time of food scarcity. An individual that is in good condition has a plump and rounded tail. Fat comprises much of its bulk. Upon emergence from hibernation this fat supply is not noticeably depleted. Brooding females in the latter part of the incubation period have the supply of caudal fat most noticeably depleted, and their tails may appear emaciated, with kinks on the terminal portion. ”

“ 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 included Eumeces 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. ”