Fig. 20.Diagrams showing typical extent of tail regeneration in skinks having tails broken at different points, × approximately1⁄2. Original parts of the tails are at the right.
Fig. 20.Diagrams showing typical extent of tail regeneration in skinks having tails broken at different points, × approximately1⁄2. Original parts of the tails are at the right.
Table 14. Records of Regeneration of the Tail in Individual Skinks Marked and Recaptured.
Under favorable conditions regeneration occurs at a relatively rapid rate. After a period of healing the new tail grows with a sudden spurt, making most of its gain in length within a few weeks. Then growth abruptly slows or ceases altogether. In young similarly rapid growth of the regenerating tail occurs, but subsequentlythe increase is more gradual corresponding to the over-all growth of the lizard. In numerous adult skinks marked, and recorded as having well-regenerated tails, the proportions recorded at subsequent captures months or years later were still just the same, demonstrating that extent of regeneration is not proportional to elapsed time. Those adult skinks having unusually long regenerated tails presumably are individuals in which the original tail was lost early in life, and the potentiality for regeneration is probably somewhat less in older individuals, especially those that have stopped growing.
Successive records of selected individuals are listed inTable 14to illustrate trends in regeneration of the tail. In those instances in which the tail is referred to as “newly broken” the separation usually occurred as an accident at the time the lizard was captured, while in those designated as “recently broken” separation had already occurred in some earlier accident but regeneration was not yet perceptibly underway. In the “Tail length” column, plus signs separate the original portion of tail, on the left, from the regenerated portion, on the right.
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. It is my impression that in adults the capacity for storage of fat is most developed in the females, and that their tails vary in proportions more than do those of males. The capacity to shed the tail easily seems somewhat inconsistent with this function of fat storage. Loss of the tail sometimes involves loss of a large amount of reserve fat. Many detached tails that were broken accidentally at the time of the skinks’ captures were weighed. In those that were broken off near the base and were not previously regenerated, weights were usually 16 to 20 percent of the lizards’ total weights.
Data obtained concerning the movements of these skinks demonstrated that individuals tend to limit their activities to small areas thoroughly familiar to them, and wander but little. Although the nature and extent of movements in reptiles in general, and in lizards especially, are poorly known, my findings are perhaps what mightbe expected from the studies of earlier workers on various other species of reptiles.
Goin and Goin (1951:29) observed thatEumeces laticepsin Florida lives in hollow stumps, each individual excluding other adults from its stump but tolerating young. Movements have not been studied in detail in any member of the Scincidae, however. The observations of Goin and Goin, and those of other authors, seem to indicate thatE. laticepsis territorial, and that each individual centers its activities about a tree or snag, regularly using the same hollow as a shelter and home base. In contrast,E. fasciatusis not territorial and has no regular home base.
The iguanid genusSceloporusis perhaps better known than any other kind of lizard as regards its movements. Studies by Newman and Patterson (1909), Stebbins and Robinson (1946), and Fitch (1940) on three different species have shown that individuals ofSceloporuskeep to small individual areas, and that territoriality is well developed, in some species at least.
Among other reptiles, turtles are much better known, as detailed studies of movements have been made on several species, of which the life histories and ecology have been thoroughly investigated (Nichols, 1939; Cagle, 1942 and 1944; Woodbury and Hardy, 1948; Stickel, 1950). They have been found to have well-defined and fairly extensive home ranges, which are not defended as territories. Studies of movements in several different kinds of snakes, by Blanchard and Finster (1933), Stickel and Cope (1947), Fitch (1949), Lowe and Norris (1950), and Carpenter (1952) have shown that these reptiles usually have definite home ranges, which may be several or many acres in extent. Their home ranges are not defended as territories against other members of the species. In general, turtles and snakes have been found to occupy home ranges that are much larger than those of lizards.
Most information concerning movements ofEumeces fasciatushas been obtained from the recapture of marked individuals. Actual distances of travel, and the time, frequency and motivation of movement was uncertain. A skink marked, recorded, and subsequently recaptured at a second location may have wandered widely in the meantime, visiting points relatively remote from either location of capture. The two points of capture may be within a home range regularly or occasionally covered by the individual in the course of its routine activities; or the second point may have been recorded only after a permanent shift of activities away from the area withinwhich the original point was located. Various types of movements probably were involved.
Interpretation of the records is difficult because of the paucity of direct observations on the behavior and movements of skinks under natural conditions. Often when one is alarmed, it will run as much as 30 feet, in a fairly direct course, to a tree or bush or rock where it can find refuge. Undisturbed individuals move about slowly and circuitously. It is difficult to keep one under observation for any length of time because of the secretive habits causing it to keep under cover, as much as possible while moving about, and to hide in response to any slight disturbance.
It is obvious that individuals shift their activities from time to time, occupying new areas either abruptly or by gradual stages. Even though a successful skink has a life span of several or many years, the populations on the small study areas were found to be much altered from one year to the next. Presumably this change was brought about largely by shifts in home ranges. Several shifts of hundreds of feet were recorded, but the chances of recovering marked individuals that moved so far were relatively poor because their movements generally took them beyond the limits of the study area to locations where recapture was unlikely. Skinks often were caught at their hiding places beneath rocks or other sheltering objects. In many of these instances it was evident from the position, temperature and state of activity of the lizard that it had been in the open but had become alarmed as the collector drew near and had retreated unnoticed to its shelter just before capture, whereas in other instances it was obviously at rest in its chosen shelter. Except for females in their nest burrows individuals were not ordinarily recaptured regularly at the same hiding places. They may seek new hiding places after each period of activity.
However many of the skinks captured were taken again, after long intervals, near the same places. Time elapsed between successive captures for different individuals ranged from one day to 47 months. Of the total of 323 recaptured by September, 1952, approximately half, 162, were taken after intervals including one or more hibernation periods. In appraising home ranges and detecting the occasional shifts over a relatively long time span, chronology of the records needs to be taken into account. Records clustering about the same center seem to indicate continued occupancy of an established home range. However, when one or more early records are well separated from one or more later records, a shift in rangeseems probable. In some instances successive records were progressively farther from the starting point suggesting two or more shifts in the same direction from an original home range.
Although recorded movements varied from a few inches to hundreds of yards, the most noteworthy feature in general was the short distance between points of capture (considered in relation to the potential mobility of the lizards) after days, weeks, months or years. In many instances no movement was demonstrable, even though successive points of capture were not exactly the same. Named natural landmarks, mostly trees, boulders and logs, well distributed over the study area, were used as a basis for locating points on the map. Direction and distance in feet to the nearest landmark was recorded for each site of capture, but for distances of more than 25 feet estimates were made to the nearest ten feet. Usually at least one landmark was available within a 50-foot radius from any point where a capture was made. Occasional estimates made for distances of more than 50 feet, or even more than 100 feet, in the absence of suitable landmarks nearby, were sources of inaccuracy. For such estimates errors of up to ten feet were common, and some errors of greater magnitude were made.
For most individuals successive sites of capture tended to cluster within a small area, but the occasional outlying capture sites indicate that each individual does range outside the area in which its activities are concentrated. These occasional excursions cannot be consistently attributed to any one ecologic requirement, nor are they limited to any particular time within the season of activity. Adult males, however, tend to make longer movements in the brief period of concentrated sexual activity, thereby increasing their chances of finding mates. Similarly, adult females may wander beyond their usual ranges in search of suitable nesting sites. The home range may be thought of as consisting of a small central portion where activities are largely concentrated, and an outer area several times as large, familiar to the animal but used to a lesser extent by it. 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.Consequently a home range may be long and narrow, with maximum diameter several times the minimum diameter.
The usual concept of home range, as a finite area with well defined boundaries is not entirely satisfactory for an animal with the habits of the five-lined skink. The skink spends much of its time in inactivity underground or otherwise concealed and sheltered, and when it does move about it takes advantage of natural travel-ways over rock surfaces, tree trunks, and logs. If a log happens to be the home range center, the skink may travel the length of the log many times without making a comparable trip at right angles to this axis of travel, although it may make short side dashes to secure food. On more extended forays, the directional sequence of movements is largely controlled by the distribution of suitable cover and travel routes, as the skink avoids both open areas and dense vegetation. Outlying portions of the home range probably are not uniformly covered but are reached only occasionally as the lizard is led along some natural travel route, or after it has visited, in succession, a series of locations attractive in providing shelter or food.
Marked skinks were recaptured at distances up to 680 feet from points of original capture. Considering only the most remote points of capture for those individuals recaptured more than once, the average recorded movement for the entire group of 323 recaptured skinks was 58 feet. This figure provides a basis for comparing vagility of this species with others. Eliminating some individuals of indefinite status, the average movement for 75 adult males was 69 feet; for 102 adult females, 45 feet; and for 112 young, 61 feet. For the adult females, home range data are biased by the fact that many were caught repeatedly at or near their nests. It is not clear whether females that do not have nests range less widely than males.
Only 15 individuals, less than five per cent, had moved more than 250 feet. These longest movements were: 680 feet, adult female, 26 months; 680 feet, adult female, 10 months; 680 feet, subadult male, one year; 650 feet, young to adult male, 22 months; 640 feet, subadult to adult female, two years; 535 feet, young male, 11 months; 510 feet, adult male, 11 months; 490 feet, young (sex undetermined), 10 months; 450 feet, young male, 13 months; 350 feet, young (sex undetermined), 101⁄2months; 335 feet, adult female 131⁄2months; 275 feet, adult male, 35 months; 275 feet, adult male, 24 months; 270 feet, young to adult male, 121⁄2months.
For those skinks caught on only two occasions, at different places, the single movement record provides some clue as to the location and size of the home range. No evidence was obtained to indicatethat the activities of these lizards center at fixed home bases. It may be assumed that any two successive captures of the same individual separated by a substantial time interval, will be distributed at random to each other within the area to which the animal’s activities are confined. The varied techniques of capture, by hand and with different types of traps, would help to secure random distribution of capture sites. If the home range were covered uniformly by the animal in the course of its activities, any two random capture sites would be on the average separated by a distance equal to half the home range diameter. If the animal tends to concentrate its activities in the central part of the home range, as seems to be the case, the capture sites will be correspondingly closer together. For the 196 skinks that were caught on only two occasions, average movement was 62 feet. Within this group the 42 adult males that were recaptured only once had averaged movements of 58 feet. One had made an exceptionally long movement of 510 feet, which obviously was not entirely within its home range. Excluding this one long movement, the remaining 41 had moved on the average, approximately 47 feet (Table 15). Among the other skinks caught only twice one of 61 females and 8 of 93 young had likewise made such long shifts that it seemed inadvisable to include them in computing the size of the home range.
Distance between points of capture showed little correlation with elapsed time. For 24 of the adult males that were recaptured in the same year they were originally marked, the average distance was 49 feet, whereas in the 17 others recaptured after one or more hibernations the average movement was 45 feet. For adult females, the corresponding figures were, respectively, 22 feet and 29 feet; and for young, 33 feet and 66 feet.
For those individuals recaptured twice, at different locations, the three points of capture show to a greater or lesser degree the position, and, in part, the extent of the home range. Of course, all three points may be concentrated near the center of the home range, or they all may be scattered along its edges. In general, however, each point will lie somewhere between the center and edge of the home range, separated from each of the other two points by a distance of, on the average, approximately a home range radius.
Table 15shows that adult males and young tend to range more widely than adult females, and that young tend to shift to new areas more frequently than do adults. Many of the recorded movements (in addition to the long ones that were excluded from the homerange computations) may have involved short shifts in ranges. If all such shifts could be definitely identified and eliminated from the computations, actual home ranges might be considerably smaller than those indicated by the present set of data. 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.
Table 15. Distances Between Successive Sites of Capture for Marked Five-lined Skinks on Study Areas, Indicating Home Range Sizes.
Individuals captured just twice
Individuals captured just three times
Individuals captured four or more times
Individuals captured just twice
Individuals captured just three times
Individuals captured four or more times
Individuals captured just twice
Individuals captured just three times
Individuals captured four or more times
Relatively few marked individuals were caught four or more times at different sites. For these individuals listed below the distribution of the sites is more or less indicative of shape and size of the home range in some instances. For some of them successive locations of capture are shown and possible home ranges are outlined in Figures21-25.
Fig. 21.Map of Skink Woods study-area, showing chief physiographic features and landmarks, and showing also successive sites and dates of capture of a marked male skink and two marked females, suggesting extent of home ranges.
Fig. 21.Map of Skink Woods study-area, showing chief physiographic features and landmarks, and showing also successive sites and dates of capture of a marked male skink and two marked females, suggesting extent of home ranges.
No. 1: Seven captures in two years, on May 13, 1950, May 12, 1951, and in 1952 on April 28, May 1, 2, 4 and 6, these seven locations well distributed over a stretch of rocky slope 275 feet in greatest diameter. The fifth location was only 20 feet from the original, whereas the last, only four days later, was the most remote, suggesting that the whole area covered may have been within a home range.No. 2: Seven captures in 46 months, skink not fully grown when first captured on June 22, 1949; 275 feet south on May 4, 1950; had moved from this second location 150 feet west northwest on June 17, 1950, and this third location together with the last four, on May 15, 1951, and May 13 and 15, 1952, and April 6, 1953, were all within a 20 foot diameter. Evidently two shifts in range were involved.
No. 1: Seven captures in two years, on May 13, 1950, May 12, 1951, and in 1952 on April 28, May 1, 2, 4 and 6, these seven locations well distributed over a stretch of rocky slope 275 feet in greatest diameter. The fifth location was only 20 feet from the original, whereas the last, only four days later, was the most remote, suggesting that the whole area covered may have been within a home range.
No. 2: Seven captures in 46 months, skink not fully grown when first captured on June 22, 1949; 275 feet south on May 4, 1950; had moved from this second location 150 feet west northwest on June 17, 1950, and this third location together with the last four, on May 15, 1951, and May 13 and 15, 1952, and April 6, 1953, were all within a 20 foot diameter. Evidently two shifts in range were involved.
Fig. 22.Sites of successive captures of two marked adult males in the Skink Woods study-area.
Fig. 22.Sites of successive captures of two marked adult males in the Skink Woods study-area.
No. 3: Six captures, all at different locations, in 22 months, on July 5 and 28, 1950, May 3 and 23, and June 21, 1951, and May 1, 1952. The 190-foot-wide area was probably all within a home range, as the fourth and fifth sites were those most remote from each other.[108]No. 4: Six captures in 21 months, in 1950 on August 14 and September 3, in 1951 on April 27 and August 21, and in 1952, on May 28 and 30. The four 1950 and 1951 locations were within a 30-foot diameter, whereas the two 1952 locations were 150 feet farther east, and even nearer together, suggesting a shift in range.No. 5: Five captures in five months, all within a 40-foot diameter, on April 24, May 7 and 28, June 14, and September 22, 1951. The first and third locations were at almost the same spot.No. 6: Five captures all at different locations, in 23 months; in 1950 on July 27, in 1951 on April 30 and May 25, and in 1952, on May 1 and June 28. The second, third and fourth locations were all within 45 feet of each other and of the first, but the last was 110 feet from the first, possibly representing a shift.
No. 3: Six captures, all at different locations, in 22 months, on July 5 and 28, 1950, May 3 and 23, and June 21, 1951, and May 1, 1952. The 190-foot-wide area was probably all within a home range, as the fourth and fifth sites were those most remote from each other.
[108]
No. 4: Six captures in 21 months, in 1950 on August 14 and September 3, in 1951 on April 27 and August 21, and in 1952, on May 28 and 30. The four 1950 and 1951 locations were within a 30-foot diameter, whereas the two 1952 locations were 150 feet farther east, and even nearer together, suggesting a shift in range.
No. 5: Five captures in five months, all within a 40-foot diameter, on April 24, May 7 and 28, June 14, and September 22, 1951. The first and third locations were at almost the same spot.
No. 6: Five captures all at different locations, in 23 months; in 1950 on July 27, in 1951 on April 30 and May 25, and in 1952, on May 1 and June 28. The second, third and fourth locations were all within 45 feet of each other and of the first, but the last was 110 feet from the first, possibly representing a shift.
Fig. 23.Sites of successive captures of three marked adult males in the Skink Woods study-area.
Fig. 23.Sites of successive captures of three marked adult males in the Skink Woods study-area.
No. 7: Four captures in two months, at approximately the same place on May 1 and 5, 1950; on May 30 had moved 35 feet farther north along ledge, and on July 1, 25 feet farther in the same direction.No. 8: Four captures in one year, all at approximately the same place along rock ledge, on June 17, 1949, and April 21, May 3 and June 15, 1950; trapped three times and once caught by hand.[109]No. 9: Four captures in one year, on April 7 and 11, and July 27, 1950, and April 14, 1951, the four different locations all within a 30-foot diameter.No. 10: Four captures in 22 months, in 1950 on July 7, and again on July 23, 175 feet farther north; on May 25, 1951, 200 feet east of second location, and on May 2, 1952, 30 feet from third location. At least one shift in range probably occurred, from 1950 to 1951.No. 11: Four captures in 36 days, in 1951 on April 30, May 8 and 15, and June 5. The last two captures were made in the same trap and were only 15 feet from the original location, but the second location was 130 feet from both. Because the time span was short and the lizard returned from the most remote point, it seems probable that all four records were within its home range.
No. 7: Four captures in two months, at approximately the same place on May 1 and 5, 1950; on May 30 had moved 35 feet farther north along ledge, and on July 1, 25 feet farther in the same direction.
No. 8: Four captures in one year, all at approximately the same place along rock ledge, on June 17, 1949, and April 21, May 3 and June 15, 1950; trapped three times and once caught by hand.
[109]
No. 9: Four captures in one year, on April 7 and 11, and July 27, 1950, and April 14, 1951, the four different locations all within a 30-foot diameter.
No. 10: Four captures in 22 months, in 1950 on July 7, and again on July 23, 175 feet farther north; on May 25, 1951, 200 feet east of second location, and on May 2, 1952, 30 feet from third location. At least one shift in range probably occurred, from 1950 to 1951.
No. 11: Four captures in 36 days, in 1951 on April 30, May 8 and 15, and June 5. The last two captures were made in the same trap and were only 15 feet from the original location, but the second location was 130 feet from both. Because the time span was short and the lizard returned from the most remote point, it seems probable that all four records were within its home range.
Fig. 24.Sites of successive captures of marked skinks, a male and two females, in the Skink Woods study-area.
Fig. 24.Sites of successive captures of marked skinks, a male and two females, in the Skink Woods study-area.
No. 12: Four captures in 11 months, all within a 50-foot diameter, in 1951, on June 1 and 26, and August 27, and in 1952, on April 29.No. 13: Four captures in 15 days, all in July 1949 within a 10-foot diameter.No. 14: Four captures in 22 months, July 22, 1950 (as subadult), in 1951, on May 8 and June 5, and on May 13, 1952. Second location 295 feet southwestof first, third 30 feet north of second, and fourth 650 feet east of second and third. Probably two shifts of range were involved.
No. 12: Four captures in 11 months, all within a 50-foot diameter, in 1951, on June 1 and 26, and August 27, and in 1952, on April 29.
No. 13: Four captures in 15 days, all in July 1949 within a 10-foot diameter.
No. 14: Four captures in 22 months, July 22, 1950 (as subadult), in 1951, on May 8 and June 5, and on May 13, 1952. Second location 295 feet southwestof first, third 30 feet north of second, and fourth 650 feet east of second and third. Probably two shifts of range were involved.
No. 1: Six captures in 26 months; in 1950 at the same place on June 4 and 13, in 1951 on May 26 it had moved from the original quarry ledge location 680 feet south southeast down the slope to the pond rock pile, where recaptured on June 9, and in 1952 on May 21 and July 22.No. 2: Six captures at four locations all within a 25-foot diameter, in 13 months; June 5, 1950, and May 25, June 18, 26 and 29, 1952. On each occasion this female was hiding in a nest burrow, but she shifted to new nest sites as a result of disturbance by the investigator or flooding when there were unusually heavy rains.
No. 1: Six captures in 26 months; in 1950 at the same place on June 4 and 13, in 1951 on May 26 it had moved from the original quarry ledge location 680 feet south southeast down the slope to the pond rock pile, where recaptured on June 9, and in 1952 on May 21 and July 22.
No. 2: Six captures at four locations all within a 25-foot diameter, in 13 months; June 5, 1950, and May 25, June 18, 26 and 29, 1952. On each occasion this female was hiding in a nest burrow, but she shifted to new nest sites as a result of disturbance by the investigator or flooding when there were unusually heavy rains.
Fig. 25.Sites of successive captures of a marked male and a marked female, each taken in three different years in the Skink Woods study-area.
Fig. 25.Sites of successive captures of a marked male and a marked female, each taken in three different years in the Skink Woods study-area.
No. 3: Five captures in 34 months, all within a radius of a few yards, at the pond rock pile, on August 8, 1949, June 5 and July 23, 1951, and May 15 and June 4, 1952.No. 4: Four captures in 34 months, all within a radius of a few yards at the pond rock pile, on August 8, 1949, June 7, 1950, May 30, 1951 and May 21,[111]1952. It is notable that this female was taken only once in each of four different years, her occupancy of this rock pile seemingly continuing throughout the duration of the study.No. 5: Four captures in two months, in 1950 on April 15, and on April 26 had moved 50 feet south; on May 23 she was approximately 50 feet from both second and third locations, and on June 5 was between second and third locations.No. 6: Four captures in 23 months, all within a 20-foot stretch of ledge, in 1950 on June 5 and 17, in 1951 on August 22, and in 1952 on May 1.No. 7: Four captures in one year, in 1951 on May 19, June 12, June 24, and in 1952 on May 21, all four locations within a 15-foot diameter.No. 8: Four captures in 23 months, in 1950 on July 5 (as a subadult), in 1951 on August 6 and 15, and in 1952 on May 28, all within a radius of a few yards at the pond rock pile.No. 9: Four captures in 13 months, on August 2 and 3, 1951, and May 28 and August 31, 1952. From the original location successive sites were 30 feet southwest, 20 feet south southwest, and 30 feet north.
No. 3: Five captures in 34 months, all within a radius of a few yards, at the pond rock pile, on August 8, 1949, June 5 and July 23, 1951, and May 15 and June 4, 1952.
No. 4: Four captures in 34 months, all within a radius of a few yards at the pond rock pile, on August 8, 1949, June 7, 1950, May 30, 1951 and May 21,[111]1952. It is notable that this female was taken only once in each of four different years, her occupancy of this rock pile seemingly continuing throughout the duration of the study.
No. 5: Four captures in two months, in 1950 on April 15, and on April 26 had moved 50 feet south; on May 23 she was approximately 50 feet from both second and third locations, and on June 5 was between second and third locations.
No. 6: Four captures in 23 months, all within a 20-foot stretch of ledge, in 1950 on June 5 and 17, in 1951 on August 22, and in 1952 on May 1.
No. 7: Four captures in one year, in 1951 on May 19, June 12, June 24, and in 1952 on May 21, all four locations within a 15-foot diameter.
No. 8: Four captures in 23 months, in 1950 on July 5 (as a subadult), in 1951 on August 6 and 15, and in 1952 on May 28, all within a radius of a few yards at the pond rock pile.
No. 9: Four captures in 13 months, on August 2 and 3, 1951, and May 28 and August 31, 1952. From the original location successive sites were 30 feet southwest, 20 feet south southwest, and 30 feet north.
No. 1: (male) Five captures in 331⁄2months; marked as hatchling on July 13, 1949, and recaptured on June 1, 1950, 175 feet northwest down slope. Subsequent locations of this lizard, as an adult, were, in 1951, on August 21 and 24, and 1952 on May 1, 80 feet east, 80 feet east, and 70 feet northeast from the second location.No. 2: (male) Five captures in a little more than one year, all within a radius of a few yards at the pond rock pile, in 1949 on August 23, and in 1950 on June 7, July 23, August 19, and September 3.No. 4: (male) Four captures in 11 months all within a 30-foot stretch along the ledge, in 1950 on July 4, and in 1951 on May 6, 14, and 25.No. 5: (male) Four captures in one year, in 1950 on September 4, and in 1951 on May 11, June 14, and August 21; the first and last locations were together separated from the second and third, also together, by about 20 feet.No. 6: (male) Four captures in 13 months, in 1950 on April 19, June 5 and June 6, and in 1951 on May 14. All four locations were linearly distributed along the ledge, the second and third near together 30 feet north of the first and the fourth 30 feet south of the first.No. 7: (sex undetermined) Four captures in one month, on April 24, and May 2, 4, and 21, 1952, well scattered within a 70-foot diameter.No. 8: (female) Eight captures in 25 months, in 1950 on June 5 and 9, and in 1951 on May 25, August 15, and September 28, and in 1952 on April 24 and 26. All were within a 150-foot diameter, the first three all within 40 feet, the fifth and sixth near together but 35 feet north northeast from the first group, the last three all within a 90-foot diameter and all to the north of the first five. At least one shift probably was involved.No. 9: (female) Five captures in 28 months, in 1950 on April 21 and May 7, in 1951 on May 3, and in 1952 on May 2 and August 27. The first three captures were all at approximately the same location, from which the fourth was 60 feet north and the fifth was 130 feet east.No. 10: (female) Five captures in 24 months; in 1950 on June 5 and 13, and July 29, in 1951 on August 21, and in 1952 on May 28. From the original[112]location successive captures were 50 feet west, 35 feet west northwest, 40 feet west, and 50 feet west.
No. 1: (male) Five captures in 331⁄2months; marked as hatchling on July 13, 1949, and recaptured on June 1, 1950, 175 feet northwest down slope. Subsequent locations of this lizard, as an adult, were, in 1951, on August 21 and 24, and 1952 on May 1, 80 feet east, 80 feet east, and 70 feet northeast from the second location.
No. 2: (male) Five captures in a little more than one year, all within a radius of a few yards at the pond rock pile, in 1949 on August 23, and in 1950 on June 7, July 23, August 19, and September 3.
No. 4: (male) Four captures in 11 months all within a 30-foot stretch along the ledge, in 1950 on July 4, and in 1951 on May 6, 14, and 25.
No. 5: (male) Four captures in one year, in 1950 on September 4, and in 1951 on May 11, June 14, and August 21; the first and last locations were together separated from the second and third, also together, by about 20 feet.
No. 6: (male) Four captures in 13 months, in 1950 on April 19, June 5 and June 6, and in 1951 on May 14. All four locations were linearly distributed along the ledge, the second and third near together 30 feet north of the first and the fourth 30 feet south of the first.
No. 7: (sex undetermined) Four captures in one month, on April 24, and May 2, 4, and 21, 1952, well scattered within a 70-foot diameter.
No. 8: (female) Eight captures in 25 months, in 1950 on June 5 and 9, and in 1951 on May 25, August 15, and September 28, and in 1952 on April 24 and 26. All were within a 150-foot diameter, the first three all within 40 feet, the fifth and sixth near together but 35 feet north northeast from the first group, the last three all within a 90-foot diameter and all to the north of the first five. At least one shift probably was involved.
No. 9: (female) Five captures in 28 months, in 1950 on April 21 and May 7, in 1951 on May 3, and in 1952 on May 2 and August 27. The first three captures were all at approximately the same location, from which the fourth was 60 feet north and the fifth was 130 feet east.
No. 10: (female) Five captures in 24 months; in 1950 on June 5 and 13, and July 29, in 1951 on August 21, and in 1952 on May 28. From the original[112]location successive captures were 50 feet west, 35 feet west northwest, 40 feet west, and 50 feet west.
Less complete records of the movements of other individuals are included along with growth data, on pages79to82and87to88.
Sizes of home ranges are affected by the type of habitat. For instance, the pond rock pile approximately 70 × 30 feet, must have constituted the entire home range for the many individuals living in it, since it was surrounded by areas that did not provide suitable habitat. No less than 212 five-lined skinks were taken in this small rock pile area in four seasons, and it is obvious that many of these were occupying it simultaneously since a substantial proportion of the total were caught there in more than one year. This rock pile provided in particularly concentrated form the essential habitat requirements, such as an abundant and varied arthropod food supply, an almost infinitely large number of hiding places beneath and between the rocks, basking sites, and flat rocks with damp soil beneath, suitable for nests. 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. For one young which grew to the size of a subadult during the period covered by the records, movements within a 150-foot diameter were recorded. 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. For 40, however, recapture records are available while they were still less than 56 mm. long. One of those was an exceptionally long movement of 215 feet, obviously involving a shift of range. For the other 39, the average movement was 34 feet, almost intermediate between the average movements of adult males and females. Observations on recently hatched young have given the impression that they keep to narrowly limited areas probably only a few yards inextent at first. For instance, at various times several members of a brood of young have been observed foraging simultaneously but independently on the same 10-foot log, within a few feet of each other. For periods of up to more than a week they had failed to disperse any farther than this from the nest, although probably never returning to the nest itself after having left. In subsequent weeks, however, the young are likely to shift their activities from the immediate vicinity of the nest site to more favorable nearby areas, and gradually extend their ranges. By the time they are one-fourth grown they are ranging over areas larger than those used by adult females.
Some of the shifts in range are probably forced upon individual skinks by changes in seasonal distribution of food, shelter and other requirements, causing them to abandon certain areas and invade others by gradual stages, without venturing far, at any time, into unfamiliar surroundings. Occasional individuals apparently get lost and undergo a period of wandering before they re-establish a home range. An individual venturing slightly beyond the border of its home range might lose its orientation and fail to return, especially if it left under conditions of stress, as when pursued by an enemy, or a rival of its own species. Several individuals originally captured in the vicinity of the quarry or nearby ledges, were subsequently recaptured at the pond rock pile more than 200 yards away. In these instances it may be that the lizard wandered from its home range along the ledge, and finding itself in thick woods, with nearly continuous canopy permitting insufficient sunlight, and with few rocks for shelter, it continued down the slope to the lower edge of the woods, crossed a ditch, and a 100-foot stretch of grassland, and finally reached the exceptionally favorable habitat provided by the rock pile.
The extent to which memory persists through the season of dormancy is little known, but great change takes place in the habitat during the colder half of the year when the lizard’s activity is suspended. Even if the area is one that is free from gross disturbance by man or large animals, the changes occurring are so great that the area might be scarcely recognizable from the lizard’s viewpoint. Herbaceous vegetation mantling the soil, at the height of its development in late summer, will have died, dried out and the leaves and stalks will have been matted down by wind, rain, and snow, and incorporated in the surface layer of soil by the next spring. Shrubs and trees having shed their leaves, present contours quitedifferent from those in autumn. Holes and crevices familiar as avenues of escape, will have been sealed, by the weather collecting and compacting surface debris. Less extensive changes are involved in the occasional blowing down of trees and dead snags, erosion of gullies, deposition of sediment and drift wood, and disintegration of logs. Many of the invertebrates which are the main food sources in late summer, are unavailable in early spring, being at different stages in the life cycle or annual cycle of abundance; and those kinds which make up the bulk of the spring diet likewise are often unavailable in fall. These changes in location of food supply, shelter, and other needs, and the seasonal change in microhabitat, breaking the established routine of conditioned responses to habitat features would seem to promote shifts in range after emergence from hibernation. The available records tend to bear out this supposition. Of the 15 skinks recorded as making long movements of more than 250 feet that almost certainly involved shift in range, only one was recaptured the same season; the other fourteen had passed one or more hibernations.
In the course of the study approximately 30 individuals were released or accidentally escaped at places other than the locations where they were originally taken. Some of these were young hatched in the laboratory, some were of unknown origin, their locality tags having been lost before release while they were being handled in the laboratory, or escaped from defective cloth bags while they were awaiting processing or release, and some taken on remote parts of the Reservation or nearby land were deliberately released on one of the study areas with the idea that they would replace skinks of the same sex and age, recently eliminated through an accident of trapping or handling. Ten were released in Skink Woods, ten at the pond rock pile, eight at the laboratory building, and two near Rat Ledge. In no instance was a transferred skink known to have found its way back to an original home range, although some might have done so with fairly short trips of only a few hundred feet, and the chances of recapturing them would have been good. Therefore it seems that homing instinct is either wholly lacking or but feebly developed. The incidence of recaptures was low, only four for the entire group, suggesting a tendency to wander away from the area of release before settling down on a home range. One young found on May 11, 1950, in the laboratory where it probably had escaped, was released in Skink Woods, and was recaptured three times in the summer of 1951, in what seemed to be a home range within 80 feet of the point of release. Another youngof unknown origin released in Skink Woods on May 18, 1950, was recaptured six days later 160 feet away. Five hatchlings from a clutch of eggs incubated and hatched in the laboratory, were released in Skink Woods on August 8, 1952. The following April two of them were recaptured, only 20 feet and 25 feet respectively, from the point of release. The movements and dispersal of this group from the point of release probably paralleled that of a typical brood dispersing from its nest after hatching under natural conditions. An adult male captured just off the Reservation was released at the pond rock pile on May 15, 1952, and was recaptured there on June 2 and June 4. In general, skinks transferred from their original location seem soon to settle down in a new range if the habitat is favorable, but establishment of a home range may or may not be preceded by an initial period of wandering.
McCauley (1939:151) examined contents of 25 alimentary tracts ofE. fasciatuscollected in Maryland as the basis for the most extensive account of the food habits yet published. One tract contained a brokenEumecestail, possibly that of the lizard that ate it, which had a recently broken stump tail. A half-grown skink contained numerousEumecesscales, and McCauley interpreted this as indicating that it had fed on another of its own species or ofE. laticeps. As no other hard parts of the assumed victim were in evidence, these scales may have been the lizard’s own slough. (In the present study it was found that eating of the slough was far more frequent than cannibalism.) Arthropod prey included: 11 orthopterans (4 undetermined, 3 unspecified grasshoppers, 2 gryllids, 1 blattid, 1 acridid); 10 coleopterans (7 undetermined, 1 each of rhynchophoran, cerambycid, carabid, staphylinid larva, elaterid adult and larva); 8 spiders; 5 pulmonate snails; 5 flies; 3 undetermined; and one each of lepidopteran larva and adult, ant, dragonfly, thysanuran, and sow bug.
In Ohio, Conant (1940:31) noted food items consisting largely of grasshopper nymphs and small beetles. He found that in captivity these skinks would eat mealworms, crickets, grasshoppers, spiders, roaches, and newborn mice, and a few individuals would lap egg from a mixture of chopped meat and eggs. One large male killed and ate a small common swift (Sceloporus undulatus). Netting (1939:162) mentioned newborn mice, birds’ eggs and small lizards as possible prey, although stating that this species is mainly insectivorous.
Taylor (1936:61) describing the feeding habits of lizards of this genus wrote: “The food consists of a very extensive variety of insects and insect larvae, Arachnida and occasionally small crustaceans. In a few specimens traces of plant material have been observed, but I regard this as being most probably of accidental introduction in the diet. Probably the most surprising fact about the diet of the forms examined is that ants are absent.” In the present study ofE. fasciatus, the trends in general bore out Taylor’s findings concerning absence of ants from the diet, although three ants were found among more than 600 other food items. These three, one of them a larva, were of the two largest species among the many kinds of ants found in the area of the study. Most of these local kinds of ants are below the minimum size of prey ordinarily taken by the skinks. Colonies of small ants,Aphenogastersp., for instance, are abundant in the soil beneath flat rocks in the same situations where the skinks are found, and constitute most of the food of the small toads,Microhyla olivacea, which were abundant in the same habitat and microhabitat as the skinks, especially in the Skink Woods study area (Freiburg, 1951:383).
Burt (1928:56) without citing specific records, stated that “The food ofE. fasciatusconsists largely of insects and spiders,” but in another paper (1928:62) he listed contents of two stomachs, including a wood roach (Parcoblatta), a cricket (Gryllus pennsylvanicus), a grasshopper, and 2 spiders (attid and lycosid). Smith, summarizing the findings of other authors (1946:350), stated that “The food consists of various small insects, insect larvae, earthworms, spiders, etc. Small vertebrates such as young lizards and mice are sometimes eaten.” In a later work Smith (1950:188) altered this statement slightly: “The food consists of almost any small moving animal, including many kinds of arthropods and even small vertebrates.”
Many authors have mentioned predation on mammals by these skinks, but without citing specific instances, which must be rare indeed, for the smallest newborn mice seem to be near the maximum size of objects that could possibly be swallowed by the largest adults of the common five-lined skink. Various early records and statements pertaining to predation on small vertebrates by five-lined skinks probably pertain in most cases toE. laticeps, which is much larger thanE. fasciatus, and more powerful.
Barbour (1950:102) recorded stomach contents of anE. fasciatuscollected in Harlan County, Kentucky, as consisting of 60 per cent Arachnida, 30 per cent adult Lepidoptera, and 10 per cent ants, byvolume. Werler and McCallion (1951:250) mentioned that on two occasions these skinks in Virginia were seen to eat tenebrionid beetles and larvae.
Webb (1949:294) fed captive skinks with field crickets (Gryllus) and noted that the lizards tended to seize them by the pronotum, and then worked forward to the head, chewing vigorously to disable them. The seized crickets attempted to defend themselves by striking the lizards’ faces and eyes with the cerci and tibial spines. Webb also offered his skinks newly hatched snails,Helix aspersa, which were noticed and fed upon when they moved. In one instance, he noted that a skink found a quiescent snail, and swallowed it after testing it with the tongue a few times.
McIlhenny (1937:232) has published a remarkable account of observations on the foraging behavior of a large adult male skink (stated to beE. fasciatusbut almost certainlyE. laticeps) in southern Louisiana, which climbed among vines on the side of a house and attacked nests of wasps,Polistes pallipesandP. bellicosus, shaking out the larvae, pausing to crush and swallow the few adults that lit on it and attempted, unsuccessfully, to sting. After many larvae had been shaken to the ground the skink descended and made a leisurely search, eating them in seemingly prodigious quantities. Several times it climbed back into the vines to shake out more larvae, and each time retrieved from the ground those it could find. After feeding to repletion it returned to its habitual shelter in a hollow live oak fifty feet from the house. In a two-week period, however, it returned frequently to raid the wasp nests in the vines, and eventually it had attacked all of the 32 nests that were originally present, completely destroying many of them.
In the course of the present study direct observations on the food habits of skinks rarely could be made in the field. Most of those seen had been alarmed by the presence of the observer, and already had begun a dash for shelter. Others not sufficiently alarmed to take cover, were affected by an observer’s presence, so that usually they ceased their normal activities and crouched attempting to conceal themselves or slithered nervously from one vantage point to another, on the alert for any sign of danger.
On September 1, 1951, a young skink (30-35 mm. snout-vent length) was discovered on the cement walk just outside the laboratory building, holding a cricket (Nemobius) which evidently it had just caught. When I came out of the building, the skink, alarmed, ran about ten feet, holding the cricket by one leg. The cricket was still alive but was nearly immobilized, except for twitching of itsantennae and mandibles, and evidently it had already been shaken and battered. After maneuvering about the cement walk the skink ran through the open door into the building. Though seeming to be uneasy at my proximity it was still mainly intent on subduing and swallowing its prey. Following, I caused the skink to take alarm. It dashed back through the door to the walk outside and still carrying the cricket, it ran along the walk to the steps leading up to another building and climbed onto the first step where its uneasiness soon subsided. The cricket was remarkably large in proportion to the skink itself, being of approximately the same diameter, with a length nearly half that of the skink’s snout-vent length. Nevertheless, in about five minutes the skink had swallowed it entire. As swallowing began, on the cement step, the skink was in bright sunshine of early afternoon. In less than a minute it seemed to become overheated, and dragged the prey back several inches into shadow. While swallowing was still in progress, it again ran forward till its anterior half was in sunshine, seemingly regulating its body temperature by these frequent shifts.
A similar encounter between a larger juvenile and a cricket (Ceuthophilus) was observed on May 9, 1953. After I had stood for several minutes beside a rock ledge in woods, my attention was attracted by a rustling sound in dry leaves. The skink, emerging onto the ledge from a cavity beneath exposed hackberry roots had its head raised high and was darting about, peering into crevices and examining its surroundings with unusual animation. After several seconds the cricket hopped into view. Possibly it had been injured already, as it moved deliberately, with short hops. Instantly the skink darted in pursuit, following its erratic course persistently, as it made several hops. In a few seconds the skink caught the cricket, bit it vigorously, and battered it against the rock ledge with violent lateral shaking. Several times the cricket was knocked from the skink’s jaws, but each time it was quickly retrieved. In a few seconds its struggles were subdued, but the skink continued to worry it, dropping it and retrieving it dozens of times. The skink seized the cricket by one of the large rear legs, which was snapped off with a sudden vigorous shake. The skink then dropped and lost the detached leg, and ran back to seize the cricket again. The performance was repeated with several other legs and the antennae, until most of the appendages were eliminated and the body was softened by continued biting and chewing. Then although the cricket was of body diameter almost as great as the skink itself, the lizard swallowed it head first, engulfing it with violent gulpingmovements. After the front end of the prey had entered the gullet, muscles of the throat and neck were brought into play in forcing it farther down. Swallowing movements were snake-like, the lizard turning its head at right angles to the body to squeeze the morsel down.
At the pond rock pile on May 7, 1952, a small adult male was watched as it moved about over the rocks. A lycosid spider (Pardosa lapidicina) carrying an egg sac was basking on an inclined rock surface. When the skink had come within a few inches, it made a sudden rush at the spider which escaped easily. As this common rock-living spider can move with almost incredible speed, skinks probably do not often catch them in the open.
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. Sight and scent seem to be about equally important in prey recognition, each supplementing the other, and often functioning simultaneously. As many of the animals preyed upon are secretive and would seldom be found in the open by day, it seems that much of the prey is found in hiding places—in leaf litter on the forest floor, beneath flat rocks or at their edges, and in chinks and crannies of decaying logs, stumps, and tree trunks. Some of the prey animals taken are of types that are more active and swift than the skinks themselves. Presumably the olfactory sense is the more important in detecting prey that is motionless or concealed. Stebbins (1948:202) studied the nasal structure ofEumeces, and compared it with that of other lizards. He concluded that the extensive mucus-secreting and olfactory surfaces suggest relatively efficient humidification of inspired air and efficient olfaction in lizards of this genus. In captivity five-lined skinks thrived when provided with ample moisture and shelter and food and kept within the proper temperature range. The reactions of these captive skinks to various small animals introduced into their terraria provided clues as to their food preferences, but also were misleading in some instances. On many occasions hatchlings and young of various sizes were kept with adults of both sexes and subadults, but no instances of cannibalism were ever recorded in captivity. Nohostility was seen except between adults, mainly in the breeding season. Young of the little brown skink,Scincella laterale, kept with adultE. fasciatus, and small enough to be eaten by them, likewise were unmolested. Small snakes such asDiadophis,Carphophis, andStoreriaplaced in terraria with the skinks evoked no strong reaction. Occasionally mild avoidance reactions were aroused but the skinks were never seen to display any hostility and readily became accustomed to such cage mates. Mealworms, the most readily available food for the captive skinks, were generally accepted by those that were hungry and sufficiently warm, but were taken with little enthusiasm. They were seldom noticed unless the skinks were within a few inches. Skinks sometimes tested them with their tongues and examined them intently then moved away without eating them. Earthworms, offered on several occasions, were not eaten. Harvestmen, seemingly of the same kind as those found in scats, were ignored by some captive individuals and taken by others but with some signs of distaste. Ants were ignored. Scarabaeid beetles, that seemed small enough to be eaten, were attacked unsuccessfully, as they were too heavily armored to be crushed in the skinks’ jaws. Wasps (Polistes) placed in terraria were avoided, as were carabid beetles and reduviid bugs. A spider placed in the terrarium usually aroused one or more skinks to animated pursuit, as soon as it moved. Even spiders that seemed to be too large to be swallowed were sometimes pursued and attacked. Occasionally freshly killed prey was taken, especially spiders and wasp larvae. Of invertebrates minute forms are not taken, while certain ants, and various others of the kinds of insects most common on the study areas and often found rather closely associated with the skinks and using the same shelters, were never represented among the recorded food items. Carabid beetles (Brachinus,Calosoma,Lebia,Harpalus,Pasimachus), and reduviid bugs (Melanolestes, etc.) seemed to be especially abundant and available, but habitually avoided possibly because of their noxious qualities. Diptera were entirely absent from the sample in the present study—they and many other insects are so much quicker than the skinks that ordinarily these insects cannot be caught. Foliage-living insects and those that are strong and persistent fliers, are rarely available as prey.
A total of 738 food items were recorded in the present study. Arachnids with 360 items, and insects with 319, together made up 92 percent of these food items. There were 334 spiders (most were not definitely identified, but four were thomisids, 40 were lycosids, and 79 were salticids, the latter group including 27 of the genusPhidippus); 26 harvestmen (Leiobunum vittatumand others); 149 orthopterans (51 ceuthophilid crickets, 31 gryllid crickets, 27 tettigoniid locusts; 17 unspecified, 14 roaches, 9 locustid grasshoppers); 80 indeterminate insects; 39 beetles (mostly carabids and scarabaeids within a narrow size range); 19 larvae (13 lepidopteran, 2 coleopteran, 1 ant, 3 indeterminate); 2 ants (Camponotus herculaneusandC. castaneus); 2 wasps; 1 moth; 1 centipede; 59 snails (31 indeterminate, 18Gastrocopta armifera, 8Retinella electrina, 1Strobilops labyrynthica, 1Hawaia minuscula); 23 sloughed skins of the skinks themselves; 2 skink eggs; and 2 skink hatchlings.
This sample is based on combined sets of data from analysis of stomach contents and of “scats.” The two sets of data present somewhat divergent trends, and perhaps neither is adequately representative of the food habits in the geographic area represented. A total of 620 food items found in scats represented an average of 1.67 items per scat, whereas in 80 stomachs containing food the average was 1.44 items per stomach. Of the skinks killed and dissected more than half had empty stomachs. Many of them were, however, found inactive in shelter so that it was obvious that they had not foraged recently. Many were not killed immediately and they may have had time to digest any food in their stomachs.
Determinations of the prey down to species were possible in relatively few instances; usually only the family or the order could be determined. Those who have attempted food habits studies of insectivorous small vertebrates will appreciate the obstacles encountered. The invertebrates available to the skinks in the area of the study included many thousands of species. A large number of these species, perhaps the majority, belong to groups still not thoroughly studied, so that their taxonomy is in a state of confusion. Ordinarily the prey is crushed in the jaws and battered on the ground before ingestion; diagnostic structures are often broken or lost, making identification far more difficult. Prey animals taken are often in immature or larval stages which lack the distinguishing features presented by adults. Even the combined efforts of a team of specialists on each of the prey groups involved probably would not have sufficed to obtain generic and specific identification of every item found. In the present study, however, all determinations were made by the writer, with the aid of the small reference collection at the University of Kansas Natural History Reservation.
The 80 specimens used for stomach contents analysis nearly all came from localities off the Reservation, but all within a ten-mile radius thereof. A dozen localities were represented by these specimens,and within each locality specimens were taken in somewhat different situations. Therefore the stomach contents analyzed represents a wide range of ecological conditions, including many different microhabitats. All the stomach contents were collected in late April, May, and June—within the first half of the skinks’ active season. Trends might be expected to differ in late summer and fall.
The food items from stomachs included: 38 spiders (8 of the salticid genusPhidippus, 5 lycosids, 4 thomisids, and the remainder unspecified); 15 insect larvae (7 of them lepidopteran and one tentatively identified as an ant,Camponotus castaneus, the rest unspecified); 13 unspecified insects; 10 crickets; 9 roaches; 9 snails (5 of themGastrocopta armifera); 7 beetles; 4 sloughs of skinks; 3 grasshoppers; 2 grouse locusts; and one each of cave cricket (Ceuthophilus?), ant (Camponotus castaneus), moth, centipede, sow bug, and egg of a skink. The egg was probably laid by the female that ate it, since she was found brooding an unusually small clutch of only three eggs.
The condition of food items found in stomachs varied greatly. Some were nearly intact, while others were fragmentary and represented by only a few of the more durable and indigestible parts. The larvae of various insects found in stomachs examined are especially noteworthy, since but little comparable material was found in the much larger group of items identified from scats.
The scatological material was even less satisfactory than the stomach material in providing determinable food items. The scats of these skinks are, roughly, 10 to 20 mm. long and two to four mm. in diameter, usually cylindrical and almost straight, and capped at one end with a white chalky deposit of uric acid. Superficially they have some resemblance to bird droppings, but are different in texture. The uric acid deposit is loose and crumbly, and much less compact than that with bird feces, and the food residue is much less completely disintegrated than is similar material in feces of birds. Common small snakes which might produce feces of similar size, include the ring-necked snake (Diadophis punctatus), the worm snake (Carphophis amoenus), and DeKay’s snake (Storeria dekayi), but their feces have a much higher moisture content, lack the definite shape of the skink scats, and ordinarily do not contain readily recognizable residue of the prey. The six other species of lizards on the Reservation, the collared lizard (Crotaphytus collaris), brown skink (Scincella laterale), prairie skink (Eumeces septentrionalis), Sonoran skink (E. obsoletus), six-lined racerunner (Cnemidophorus sexlineatus) and glass “snake” (Ophisaurus attenuatus) might producescats indistinguishable from those of the five-lined skink. However, none of these lizards except the relatively rare and secretive brown skink, occurred in either of the two situations where most of the scats were collected and it is highly improbable that the scat collection included any material from species other than the five-lined skink.
The scats consist mainly of chitinous fragments of arthropod prey. Usually the prey fragments are so well comminuted, mixed, and scattered that reconstruction is difficult. Degree of disintegration differs greatly, depending not only on the type of prey eaten, but probably also on the condition and temperature of the lizard, and the amount of other food in its digestive tract. Arthropods which have recently undergone ecdysis and have the exoskeleton still thin and soft are no doubt digested much more completely than those that have more heavily sclerotized parts. In spiders the chelicerae are more resistant to digestion than are other parts of the exoskeleton, and frequently appear, intact or nearly so, in the scat contents. The fangs being even more resistant, were sometimes found separately when no other cheliceral parts were recognizably preserved. Frequently large fragments of the carapace, with some of the eyes or all of them, were found. Spider abdomens sometimes were distinguishable, but were collapsed and compressed. Spider legs conspicuous in most of the scats, were so broken, tangled, and distorted that they were of little diagnostic value. In harvestmen, dorsal shields were nearly always fairly intact; but only small fragments of the elongate slender legs were found and they were mostly broken off when the attacking skinks battered the phalangid against the ground before swallowing it. The horny outer wings of crickets, roaches, and beetles usually were in recognizable though fragmentary condition. Occasional heads of insects often were found fairly intact. Insect legs were sometimes intact, sometimes broken into sections or crushed and fragmented. The thorax was usually represented by scattered fragments of chitin, and the abdomen by the separate chitin bands of each body segment.
Shells of snails were sometimes found nearly intact in the scats, although showing the effect of the digestive juices in their extreme brittleness. In other instances all that remained of the shell was the inner columella, and small scattered fragments.
Certain of the items eaten were probably so thoroughly digested as to leave either no hard parts at all, or minute and nondescript parts that were not recognized. The common small slugDeroceras laeve, for instance, would seem to be just as suitable and availablefor food as the various kinds of snails, but it was not recorded in either stomachs or scats. Having no hard parts except the vestigial internal shell, it probably would not be recognized in scats, even though it had been eaten. Various insect larvae, having thin outer cuticles and virtually no hard sclerotized structures except in the head, likewise probably would leave no recognizable parts. Molted skin of the skinks themselves seemed to be little altered by the digestive processes.
Table 16. Frequency of Occurrence by Months of Various Types of Prey in a Collection of 371 Scats of Eumeces fasciatus.