Life History and Ecology of the Five-Lined Skink, Eumeces fasciatus. Henry S. Fitch
in its behavior, and is inactive in inaccessible shelters during the greater part of the year.
The five-lined skink generally occurs along with a characteristic set of community associates in a particular type of situation. It is a predator on various small animals, mostly invertebrates. For some of the many prey species the effect is certainly negligible, but for others its predation may be a major ecological factor. In areas where optimum habitat conditions exist its biomass may exceed that of any other insectivorous animal, and in such situations it assumes a major role as a predator and as a competitor with other insectivorous types. In turn it provides part of the food source of various larger predators, including reptiles, birds and mammals. It is a host and carrier of various parasites, including at least one species that regularly attacks humans—the common chigger. It is not evident on the basis of the present findings that the skink is either harmful or beneficial to any perceptible degree, in its over-all effect on human affairs and economy. Nevertheless, there probably are various unsuspected relationships.
In the course of my field study many workers on the University of Kansas Natural History Reservation helped by capturing skinks; especially Sydney Anderson, Richard Freiburg, John Hawken, Dennis G. Rainey and Lewis L. Sandidge. Mr. Robert Gordon very kindly furnished information on specimens in the Tulane University collection, which served as a basis for comparing the breeding schedule of the southern population with that of E. fasciatus in northeastern Kansas. Dr. W. J. Breckenridge kindly permitted examination of material in the University of Minnesota Museum of Natural History. Dr. Edward H. Taylor has made helpful suggestions from time to time. Mr. Richard B. Loomis helped me in various ways with the field work, and made available his personal field notes with records of predation on Eumeces by various snakes. Dr. E. Raymond Hall, Director of the Museum of Natural History, has critically examined the manuscript, and has been helpful in various ways. The line drawings and graphs, with the exception of Figures 8 and 9, were made or completed by Mrs. Louise Brunk, artist for the Museum.
The study here reported on was initiated in May 1949, and was continued through 1950, 1951 and 1952. A few observations made in 1948 have been included. Various separate items of information obtained in 1953 have likewise been incorporated especially where histories of individual skinks are presented, but the manuscript was completed in essentially its present form in the fall of 1952.
Methods
Skinks were obtained by active search; rocks and boulders were lifted up and the skinks thus exposed were seized by hand before they had time to escape. This method was effective when the skinks were using rocks for shelter and when temperatures were low enough so that they were slow and sluggish, but in hot weather the skinks were so quick and active that those exposed usually escaped. Usually skinks could be obtained much more easily by trapping. At the pond rock pile (Fig. 26), for instance, shelter was so readily available that the skinks could seldom be caught by hand. Gallon cans buried with the tops open flush with the surface of the ground served as pitfalls and were effective when they were carefully placed, at the bases of rock ledges or logs or stumps, where the skinks were most likely to fall into them. Most of the skinks recorded at the rock pile were caught by this method, and sometimes several were caught together in the same pitfall. Ordinarily each pitfall was covered with a large flat rock, propped against a nearby object to leave ample space for the skink to enter beneath it. The rocks provided protection from direct sunlight, from rain, and from predators. Still another method of catching skinks was with wire screen funnel traps (Fitch 1951:77). These funnel traps were of different sizes, and were made of different kinds of wire mesh. They were set for reptiles that were mostly larger than five-lined skinks, and those having quarter-inch wire mesh permitted many of the immature skinks to escape. Most of these funnel traps were from about one foot long and five inches in diameter, to about twice these dimensions, with funnel openings about 1.5 inches in diameter. Some made of 1⁄8 inch wire mesh, six or seven inches long, and three or four inches in diameter, with funnel openings only a little larger than the body diameter of an adult skink, were found to be suitable for skinks of all sizes, and were used successfully at the pond rock pile. Most of the skinks trapped were adult males, and they were taken chiefly in May. The funnel traps were generally placed at the edges of rock outcrops, boulders or logs, where skinks were likely to be intercepted in their usual travel routes. Each method of collecting skinks resulted in occasional mortality to them but most losses were in those caught in funnel traps. In these traps they sustained rapid loss of moisture, and were usually somewhat desiccated. Two or more adult males were often caught together, and in most of these instances the first one caught probably served as bait attracting another and arousing his pugnacious interest. Injuries were frequent, and some deaths occurred because in the close confines of a trap the loser in a fight was unable to escape further attacks.
Most of the skinks caught were examined, and released within a few minutes. Snout-vent length was measured by holding the skink against a rigid transparent plastic millimeter ruler and exerting a slight pull on each end of the lizard until it tired and relaxed its muscles, eliminating bends and kinks. Even with such precaution, precise measurements could not be obtained and the readings often varied a millimeter or more for the same skink measured two or more times on the same day. Tail length was similarly recorded with separate readings for the original and regenerated portions. Also recorded were sex (when discernible), color and pattern, breeding data, injuries, general condition, and sometimes temperature. Many of the skinks were brought to the laboratory, and were weighed to the nearest tenth of a gram.
Occasional trips were made to localities away from the Reservation to collect skinks. Some of those obtained were kept under observation in terraria where their behavior was studied. Most were preserved and were used for data on habitat preferences, seasonal changes in the gonads, size group, stomach contents, and various other items of information.
Description
The scutellation and osteology have been described in detail by Taylor (1936:39–48 and 199–206) and others, and need not be repeated. The five-lined skink is slender and elongate, somewhat snake-like (though much less so than many other skinks) as the head, neck, body, and tail are not well set off from each other, and the sleek, streamlined contours are broken only by the small limbs protruding from the sides of the body. The body is slightly flattened laterally, tending toward quadrangular shape in cross section. The head is wedge-shaped, with a short, rounded snout. The nostrils are laterally placed, well back from the tip of the snout. The eyes are small and deep set; the iris is dark. The neck is thick and strong, nearly as long as the head. The torso is 31⁄2 to 4 times as long as it is wide. The tail is almost square in cross section at its base, but is circular in cross section for most of its length. The limbs are moderately developed; when adpressed along the sides of the body, the forelimb and hind limb overlap by a length about equal to the longest toes of the forelimb. The limbs are pentadactyl and all the toes are well developed and have claws (Figures 1 and 2). The claws are short, and are curved in such a manner that their tips are directed downward, each approximately at right angles to the axis of the toe (Figure 2b). The limbs are moderately thick and muscular. The upper arm and forearm segments are of approximately equal length, as are the femoral and tibio-fibular segments of the hind limb.
Fig. 1. Antipalmar view of right front foot, × 9.
Fig.