Life History and Ecology of the Five-Lined Skink, Eumeces fasciatus

Chapter V: Part 5

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=======+==================+==========+=====================+======+============================
| |Snout-vent| |Weight|
| Date | length | Tail length | in |
| | in mm. | in mm. | grams| Remarks
-------+------------------+----------+---------------------+------+----------------------------
No. 1. |Male | | | |At an age of 33 months
|April 12, 1950| 43 | 71 | 1.5 | this male was far short
|August 30, 1950| 56 | 56 + 21 | 5.4 | of maximum size, and
|May 23, 1951| 68 | 59 + 32 | .... | smaller than some
|April 28, 1952| 73 | 62 + 38 | 6.6 | males a year younger;
| | | | | all four captures within
| | | | | a 65-foot diameter.
| | | | |
No. 2. |Male | | | |At an age of approximately
|July 5, 1950| 61 | 92-1/2 (regenerated)| 5.2 | one year this
|July 28, 1950| 64 | 97 (regenerated) | 5.4 | male was approaching
|May 3, 1951| 68 | 96 (broken stub) | 5.8 | small adult size; when
|June 21, 1951| 72 |101-1/2 (regenerated)| .... | last captured at an age
|May 1, 1952| 78 |101 (regenerated) | .... | of 34 months, he was a
| | | | | large adult. All five
| | | | | records within a 190-foot
| | | | | diameter.
| | | | |
No. 3. |Male | | | |This skink was nearly a
|June 22, 1949| 65 |111 | .... | year old and nearing
|May 4, 1950| 72-1/2 |115 | 7.3 | adult size when first
|June 17, 1950| 73 |116 | 7.8 | captured; recaptured
|May 15, 1951| 80 |125 | .... | in each of the four
|May 13, 1952| 82 |125 | .... | succeeding years, he
|April 6, 1953| 82 |104 (regenerated) | .... | showed slowing growth.
| | | | | He was near the maximum
| | | | | size at the time of his
| | | | | last capture when he
| | | | | was about 57 months
| | | | | old, and evidently had
| | | | | stopped growing (for
| | | | | movement see No. 2,
| | | | | p. 110).
| | | | |
No. 4. |Female | | | |This individual, marked
|July 13, 1949| 27 | 34-1/2 | .... | when less than two
|June 1, 1950| 54-1/2 | 93-1/2 | 3.1 | weeks old, had grown
|August 21, 1951| 74 |119 | .... | to nearly the maximum
|May 1, 1952| 76 |123 | 10.0 | female size at an age of
| | | | | 34 months; all four
| | | | | captures within a
| | | | | 175-foot diameter.
| | | | | (See Figure 24).
No. 5. |Female | | | |
|April 15, 1950| 43 | 70 | 1.4 |All six records within a
|June 5, 1950| 52-1/2 | 87 | 2.8 | 65-foot diameter (See
|May 25, 1951| 71 | 82 + 29 | .... | Figure 21).
|September 28, 1951| 73 |111 (regenerated) | .... |
|April 26, 1952| 74 |113 (regenerated) | 7.4 |
|April 24, 1953| 76 |114 (regenerated) | .... |
| | | | |
No. 6. |Female | | | |Hatched in July 1949,
|April 21, 1950| 46 | 75 | 2.1 | this skink had attained
|May 7, 1950| 48 | 15 (broken stub) | 2.0 | the maximum female
|May 3, 1951| 74 | 29 + 57 | 8.5 | size at an age of a little
|May 2, 1952| 78 | 25 + 64 | .... | more than three years;
|August 27, 1952| 79-1/2 | 95 (regenerated) | 8.3 | (for movement see
| | | | | Figure 25).
| | | | |
No. 7. |Female | | | |Hatched in July 1949,
|June 5, 1950| 51 | 82 | 2.5 | this skink was 11
|July 13, 1950| 59 | 93 | 3.9 | months old and about
|July 29, 1950| 64 | 98 | 4.4 | half-grown when it was
|August 21, 1951| 69 | 80 (broken stub) | 5.0 | marked. When last
|May 28, 1952| 73 | 83 + 9-1/2 | .... | caught at an age of 35
| | | | | months it was of average
| | | | | adult female size,
| | | | | having grown less than
| | | | | numbers 4 and 6 at the
| | | | | same age. All five captures
| | | | | were within a 60-foot
| | | | | diameter (Fig. 24).
| | | | |
No. 8. |Female | | | |Hatched in July 1949,
|April 26, 1950| 50-1/2 | 78-1/2 | 2.7 | this skink was of average
|May 24, 1951| 74 |107 (regenerated) | .... | adult female size
|April 28, 1952| 78 | 93 (regenerated) | 8.5 | and was breeding in
|April 23, 1953| 80 | 93 (regenerated) | .... | May 1951; it grew
| | | | | nearly to maximum female
| | | | | size in the next 11
| | | | | months. All captures
| | | | | within a 70-foot diameter.
No. 9. |Female | | | |
|July 5, 1950| 60 | 95 | 4.5 |All three captures at the
|August 6, 1951| 71 |106-1/2 | 5.6 | same site.
|May 28, 1952| 72 |110 | 8.5 |
| | | | |
No. 10.|Male | | | |Hatched in July 1949,
|April 23, 1950| 46-1/2 | 66 (regenerated) | 1.8 | this male grew less
|June 13, 1950| 52-1/2 | 26 + 3 | 2.7 | rapidly than most, and
|September 2, 1950| 66 | 32 + 51 | 6.2 | in the spring of 1953
|May 29, 1951| 67 | 33 + 58 | .... | was smaller than some
|August 3, 1951| 70 | 94 (regenerated) | .... | others that were a year
|March 27, 1953| 74 | 78 (regenerated) | 7.1 | younger, or even two
| | | | | years younger.
No. 11.|Female | | | |
|April 26, 1950| 50-1/2 | 78-1/2 | 2.7 |This skink had attained
|May 24, 1951| 74 | 87 | .... | maximum female size
|April 28, 1952| 78 | 72 + 21 | 8.5 | when she was a little
|April 23, 1953| 80 | 73 + 20 | .... | less than four years old.
-------+------------------+----------+---------------------+------+----------------------------

Differences in their growth rates therefore reflect differences in sex, individual vigor, and local situation, in individuals living at the same time and within the same general environment.

Changing weather, and other factors that vary from year to year cause marked differences in the dates of important events in the annual cycle, and in the stage of development at any given date. Data are available for five successive annual broods of young, those of 1948, 1949, 1950, 1951, and 1952, and each brood differs from the others to some extent, as shown in Figures 11 to 13. In 1949, for instance, young hatched relatively early, and probably most of them were active by the middle of July. They made rapid growth in August, averaging larger than young hatched in other years on any given date in late summer. However, they retired into dormancy early in the fall. Cool and dry weather in early September ended their activity for the season. In 1950, young hatched, on the average, at least three weeks later, about the first of August, but they remained active until late in September, and by hibernation time had partly caught up to the stage of development attained by the young of 1949. Most young of 1951 hatched late in the first half of August, and at first were smaller than those of 1950 and much smaller than those of 1949 on corresponding dates, but favorable weather in the early fall hastened their development. By early September they had caught up and passed the stage of development of young of 1950 and by the time they retired to dormancy in late September, they had reduced by half the size-advantage of the young of 1949 at the time these latter retired into hibernation. The young of 1951 appeared to be few in numbers, and a lack of competition may have been a factor in their rapid early development.

The young of 1948, first sampled after their emergence from their first hibernation in mid-April of 1949, were then somewhat intermediate in size as compared with those of 1949 and 1950 at the same times of year. Their subsequent development was rapid; by late May they had caught up and passed the stage reached by the 1949 young at the same time of year. The young of 1950 after having a late start, were further set back by cold weather in April 1951 delaying their emergence from hibernation. As a result they were still unusually small in late April and May. Even though they grew rapidly subsequently, they were consistently smaller than those of other broods on corresponding dates. Favorable fall weather prolonging the 1951 growing season into late September beyond the time of retirement in other years may have permitted many of them to attain adult size.

The varying fortunes of the several annual broods studied were closely correlated with weather trends, and suggest possible effects of slight changes in climate. An unfavorable sequence of weather might bring about drastic reduction of the population without causing any direct mortality. A late spring in two successive years would have cumulative effect in delaying emergence and breeding of adults the first year, and delaying in the second year emergence of the young, already retarded by the lateness of their hatching. If this sequence were followed by onset of unusually cool and dry weather in early September, or even in late August, the young might be "caught short," and forced to hibernate while still in the 50-60 mm. size class. Emerging the following spring, they might have failed to mature sexually, reducing by perhaps half the number of productive adults. At the northern extreme of the species' range, length of growing season may be more critical than extremes of temperature in limiting the numbers and distribution. Growing seasons that average long enough and warm enough to permit attainment of maturity by onset of the second hibernation period may be essential to the species. While no two annual broods of young in the same locality come under exactly the same weather influences, extremes of retardation or acceleration continuing throughout development are relatively rare. Retarding effects of unfavorable weather causing delayed breeding and hatching, may be offset by prolongation of warm weather in the fall thus delaying hibernation, or by warm spring weather hastening emergence from hibernation.

Under favorable conditions an adult female produces about ten offspring annually of which about half are females. It is calculated that if all survived, after ten breeding seasons, the progeny of an original female might have increased to a population of more than 97,000, under the climatic conditions of eastern Kansas, permitting attainment of breeding maturity late in the second year of life. In the same ten year period under climatic conditions delaying maturity until late in the third year of life (as seems normally to occur in _E. septentrionalis_ and _E. skiltonianus_, and probably in _E. fasciatus_ at the northern edge of its range) the original female would have produced a population of somewhat less than 7,800 assuming that all survived. With a long growing season such as occurs in the southern part of the range, it seems theoretically possible (though not probable) that individuals might mature before the end of their first year, in time to participate in the next breeding season. If this should occur the original female might produce a population of more than 120 million by the end of the tenth breeding season.

CHANGES IN PATTERN

Progressive alteration of the color pattern is more rapid in males than in females and is synchronized with growth. During the first year of life changes in the pattern are gradual, and consist chiefly of loss in vividness. The blue of the tail is slightly dulled. The light lines become suffused with brown and the dorsolateral dark areas become paler, with light brown areas appearing on the corners of the scales and gradually spreading to replace the original black. In skinks that are in the second year of life the striped pattern although still conspicuous is made up of two shades of brown instead of the earlier black and white markings.

Even in hatchlings, the dorsal part of the rostrum and the inter-nasals are of a somewhat neutral brownish color, matching neither the light lines nor the dark interspaces of the striped body pattern. With advancing age this neutral brown color gradually spreads posteriorly on the head so that the striking lyrate marking of the bifurcated dorsal stripe on the head in the juvenile become obscured by the time the skink has grown to small adult size, at 21 months. The top of the head is then dull brown, with a slightly mottled appearance caused by the different intensity of pigmentation in different areas. The stripes though still discernible, are faint and inconspicuous. Dorsally, on the body, the stripes are still conspicuous, but are dull and lacking in contrast. At this stage, the dark lateral area is retained with intensity of pigmentation scarcely diminished.

Table 13. Normal Range of Variation in Dorsal Striping of Head
and Body, and in Color of Tail According to Age and Sex.

In tracing the gradual ontogenetic changes in the striped pattern, from the vividly contrasting colors of hatchlings to the dull, patternless coloration of old adult males, five descriptive terms have been applied to the successive stages: "sharp," "distinct," "dull," "faint," and "absent." To most individuals below minimum adult size, the term "sharp" is applicable, although there is some loss in vividness in the larger young, as compared with hatchlings. Fading of the original striped pattern proceeds more rapidly on the head than on the body. Upon emergence from their second hibernation at an age of about 21 months, the skinks, mostly grown to adult size, and ready to mature sexually, still show but little sexual difference. They retain the hatchling pattern essentially unchanged, but with colors dulled and contrasts reduced. Within a few weeks the newly matured males undergo relatively rapid color change as the breeding season progresses. The stripes tend to fade and blend into the dark areas adjacent to them. In the two-year-old males stripes are distinct to dull on the body and faint or absent on the head, while in females of the same age group, body stripes are sharp or distinct.

Table 13 refers to adult pattern and coloration as they appear in the breeding season. After the breeding season, in late spring and early summer, when the red suffusion of the head and neck has faded in adult males, the original striped pattern, after having been almost completely suppressed may again become discernible. Individuals of the same size differ in extent of pattern change, and the color descriptions made of individuals were not sufficiently detailed to show fully the changes occurring between successive dates of capture. However, most large adult males taken later than mid-June had at least some trace of the striped body pattern and many of them had become so much like females in appearance that close scrutiny was necessary to determine their sex. They were especially like females in having the dark lateral area extending forward onto the cheek and setting it off sharply from the paler temporal region above it. In breeding males the head has no such dark markings and is suffused with red.

GROWTH AND REGENERATION OF THE TAIL

Even among those skinks which have never broken their tails there is a wide range of variation in relative length of tail. This is partly a matter of relative growth since the proportions change during the course of development. Also there may be slight sexual difference and there is much individual variation. In fetuses still well below hatching size, the tail length is less than the snout-vent length. For instance, an egg in a natural nest 12 days short of hatching contained a fetus that had a snout-vent length of 14 mm. and tail length of 12 mm. (Figure 18). In the late stages of fetal development the tail growth is relatively rapid. At hatching, the tail is considerably more than half the total length. In a large series of young with snout-vent lengths from 30 mm. down to hatching size of 25 mm. or less, the tail length averaged 130.8 per cent of snout-vent length. In larger young, up to a snout-vent length of 40 mm. or more, the tail continues to lengthen more rapidly than the body. In skinks that are about two thirds grown, the tails average relatively longer than in either larger or smaller individuals. In the sample representing the size class 50-54 mm. snout-vent length, the tails average 163.3 per cent of the snout-vent lengths, whereas in groups of adults of various sizes and both sexes, the tail length is near 155 or 156 per cent of the snout-vent length. Sexual dimorphism in tail length is slight if it exists at all; in adult males, tails averaged a little longer than in adult females.

When a skink's tail is broken, there is almost no loss of blood. The fractured surface is rough and irregular, with exposed muscle masses protruding on the detached end and corresponding concavities on the end of the stump tail retained by the lizard. The concavities are soon filled with oozing blood, and a thick scab forms. As healing begins, the broken end presents a flat, slightly irregular surface. When the scab is sloughed off, a slightly convex surface of delicate, pale-colored new skin of the regenerating tail, is exposed. At first, no scale structure is discernible. As growth proceeds, the new tail takes on a bluntly conical shape. During the early stages of growth, it is well set off from the original portion by the abrupt taper at the point of contact and by its paler coloration and different texture, with no scales discernible at first, and later with fine and granular scalation. The new tail elongates until the more abrupt taper beyond the point of the break is no longer noticeable, and the coloration, surface texture and scalation match that of the original portion so closely that it is difficult to determine where the break occurred or even to ascertain that there has been one. On the regenerated tail, however, the scales are less uniform in size and less regular in shape. The regenerated tail, being different from the original in internal structure, with a cartilaginous rod replacing the vertebral column, is less fragile and subsequent fractures are most likely to be on the part proximal to the regeneration. Nevertheless, fractures of regenerated tails occur occasionally. In old skinks especially, the tail eventually may consist of three or more distinct segments including the basal remnant of the original tail and the successive regenerations. When a break in the regenerated tail occurs, the detached portion is relatively inert, and is capable of only feeble twitching movements in contrast with the lively wriggling normally displayed in a newly detached tail that includes part of the central nervous system.

Rate of growth in the regenerating tail is controlled by a variety of factors, such as age, condition, and activity of the individual, and site of the fracture. A break occurring early in the skink's lifetime results in regeneration more complete than occurs in an adult sustaining the same type of injury. The regenerated tail eventually may be longer and thicker than the lost part if the lizard is young and still growing. But the regenerated tail is never so long as the original one would have been. Regeneration is most extensive in those tails broken near the base. The farther from the base the break occurs the shorter is the part regenerated. As a result, tails that have had time to regenerate do not differ greatly in total length regardless of where the break occurred. However, the nearer the break is to the base, the shorter is the total tail-length after regeneration (Figures 19 and 20). If only the tip of the tail is lost, regeneration may not occur. In the skinks examined that had regenerated tails the proportions varied over a wide range. Presumably, in many, growth of the regenerated portion was still incomplete.

Table 14. Records of Regeneration of the Tail in Individual Skinks
Marked and Recaptured.

=================+==================+==========+========================
| |Snout-vent|
Age and Sex | Date |length | Tail length
| |in mm. | in mm.
-----------------+------------------+----------+------------------------
No. 1. |June 1, 1951| 73 | 38 (newly broken)
Adult male |June 26, 1951| 73 | 38 + 14
|August 17, 1951| 76 | 40 + 45
|April 29, 1952| 76 | 40 + 45
| | |
No. 2. |May 28, 1949| 51 | 46 (newly broken)
Immature |October 15, 1949| 69 | 51 + 21
| | |
No. 3. |June 11, 1950| 49 | 49 (newly broken)
Immature |September 2, 1950| 63 | 63 + 31
| | |
No. 4. |August 10, 1950| 62-1/2 | 60 (newly broken)
Immature female|June 14, 1951| 68 | 62 + 17
| | |
No. 5. |August 14, 1950| 67-1/2 | 77 + 4-1/2
Adult male |September 3, 1950| 68-1/2 | 77 + 6-1/2
|April 27, 1951| 69 | 78 + 9
| | |
No. 6. |April 7, 1950| 67 | 38 (newly broken;
Adult male | | | separated end 66)
|July 27, 1950| 71 | 39 + 47-1/2
| | |
No. 7. |May 28, 1951| 70 | 18 (newly broken;
Adult male | | | separated end 100)
|June 14, 1951| 71 | 18 + 1
|September 22, 1951| 76 | 19 + 29 + 7-1/2
| | |
No. 8. |June 12, 1951| 72 | 33 (recently broken)
Adult male |July 28, 1951| 76 | 36 + 31
| | |
No. 9. |May 2, 1951| 45 | 47 + 1
Juvenile |May 14, 1951| 45 | 47 + 3
|May 19, 1951| 45 | 47 + 5
| | |
No. 10. |June 7, 1952| 64 | 51 (recently broken)
Subadult female|June 24, 1952| 64 | 51 + 11
| | |
No. 11. |August 19, 1949| 42 | 40 (newly broken)
Juvenile |June 13, 1950| 58-1/2 | 58 + 28
|August 5, 1950| 63 | 62 + 31
| | |
No. 12. |May 17, 1951| 78 | 20 (newly broken)
Adult male |June 12, 1951| 78 | 20 + 13
-----------------+------------------+----------+------------------------

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 subsequently the 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 in Table 14 to 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.

Movements

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 might be expected from the studies of earlier workers on various other species of reptiles.

Goin and Goin (1951:29) observed that _Eumeces laticeps_ in 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 that _E. laticeps_ is 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. fasciatus_ is not territorial and has no regular home base.

The iguanid genus _Sceloporus_ is 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 of _Sceloporus_ keep 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 of _Eumeces fasciatus_ has 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 within which 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 range seems 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), 10-1/2 months; 335 feet, adult female 13-1/2 months; 275 feet, adult male, 35 months; 275 feet, adult male, 24 months; 270 feet, young to adult male, 12-1/2 months.

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 indicate that 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 15 shows 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 home range 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.

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 Figures 21-25.

ADULT MALES

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. 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.

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. 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.

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. 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 southwest of first, third 30 feet north of second, and fourth 650 feet east of second and third. Probably two shifts of range were involved.

ADULT FEMALES

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. 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, 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.

YOUNG

No. 1: (male) Five captures in 33-1/2 months; 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 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 pages 79 to 82 and 87 to 88.

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Life History and Ecology of the Five-Lined Skink, Eumeces fasciatusChapter V: Part 5

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