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.
=======================+============+==========+===========
| | | Number
| Average | | of skinks
| maximum | | discarded
| distance | Number | from
| in feet | of | sample
| between | skinks | because of
Age, Sex and Number | points | included | relatively
of Captures | of | in | long
| capture, | sample | movements,
| and | | indicative
| extremes | | of shifts
| | | of range
-----------------------+------------+----------+-----------
Adult males | | |
Individuals captured | | |
just twice | 47 (225-0) | 41 | 1
Individuals captured | | |
just three times | 47 (130-0) | 18 | 0
Individuals captured | | |
four or more times | 91 (200-0) | 17 | 2
| | |
Adult females | | |
Individuals captured | | |
just twice | 16 (90-0) | 56 | 4
Individuals captured | | |
just three times | 25 (90-0) | 25 | 3
Individuals captured | | |
four or more times | 28 (90-0) | 15 | 1
| | |
Young | | |
Individuals captured | | |
just twice | 45 (160-0) | 85 | 8
Individuals captured | | |
just three times | 46 (150-0) | 14 | 0
Individuals captured | | |
four or more times | 82 (175-0) | 14 | 2
-----------------------+------------+----------+-----------
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.
[Illustration: 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.]
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.
[Illustration: 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.
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.
[Illustration: 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.
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.
[Illustration: 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
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.
[Illustration: 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, 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.
Sizes of home ranges are affected by the type of habitat. For instance,
the pond rock pile approximately 70 x 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 in extent 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.