Data obtained from trailing and various methods of recapture at the
Damm Farm indicated that each individual used only a small part of the
total study area in the course of daily activities and tended to
remain within a restricted area for a long time.
The number of recaptures of no individual was great enough to permit
application of refined calculations of size of home range as described
by Odum and Kuenzler (1955). For individuals that were recaptured six
or more times, or individuals for which adequate trailing records were
available, the area enclosed by a line joining the peripheral points
of capture was considered adequately representative of the home range
of that individual, unless recaptures were all within a few feet of
each other or lay in an approximately straight line. If less than six
records of recapture were available, home range was estimated, in the
manner described by Fitch (1958:73), by averaging the distance between
successive points of recapture and letting this average represent the
radius of home range; the actual area of home range was determined by
the formula, [pi](R)A squared, for the area of a circle.
Size of home ranges of males and females did not differ significantly
and data for the two sexes were combined in the final analysis. The
average radius of the home ranges of 44 adults (captured a total of
146 times) was 278 feet (extremes, 71 to 913) when computed by
measuring the distance between successive captures; the average area
of these home ranges was 5.6 acres. Data from 10 turtles that had been
recaptured only once were combined with data from 34 turtles that had
been recaptured more than once when it was found that the average size
of home range in these two groups did not differ significantly. Data
concerning the home ranges of eight of the 44 individuals were
sufficient to permit actual measurement of home ranges with a
planimeter; home ranges of these eight individuals had an average area
of five acres (extremes, 1.2 to 10.2).
A minimum home range could theoretically consist of the smallest area
in which adequate food and shelter were available. Under favorable
conditions a turtle could stay in an area ten to twenty feet in
diameter. Although several such favorable small areas existed on the
Damm Farm, box turtles seldom stayed in one for more than a day or
two. Seemingly, therefore, factors additional to food and shelter
influence size of home range. At the Damm Farm these additional
factors seemed to be: rock fences that acted as physical barriers;
areas that were cultivated, barren, or otherwise unfavorable, acting
as ecological barriers; and, cowpaths and ravines that offered
relatively unobstructed routes along which box turtles tended to move.
One subdivision of the main pasture, the northwest corner area, is an
example of a relatively small natural area in which many individual
box turtles had home ranges. This tract of 28 acres was roughly
triangular and was bordered on two sides by rock fences that contained
no gates or other passageways. On its third (southeastern) side the
area sloped into a deep ravine. Habitat in this subdivision of the
pasture (as well as in the other two subdivisions) was especially
favorable for box turtles because of permanent water, rocky slopes,
ravines, and several fruit trees. Box turtles usually foraged near the
rock fences and the ravine (where dung was more abundant than in other
parts of the area), and tended, as they foraged, to move parallel to
these barriers. Turtles crossing the area eventually came either to
one of the fences or the ravine. Therefore, most of the turtles in the
northwest corner area eventually completed a circuit of the area.
Turtles that came to the ravine tended to move along its bottom or
sides. Several turtles were known to cross the ravine and to forage in
the grassy area on its southeastern side. These turtles usually
re-entered the ravine by way of smaller side-ravines. Of 22 box
turtles known to have home ranges in the northwest corner area, only
two individuals (both gravid females) were known to leave the area in
the period in which observations were made.
Two other subdivisions of the main pasture--the house pond area and
the southern ravine area--although not so distinct as the northwest
corner area in terms of limiting barriers, nevertheless constituted
separate areas of favorable habitat, each of which contained a number
of individual home ranges. Although the two areas were not far apart,
but little movement was observed of turtles from one area to the
other. The home range of only one turtle, an adult female, was known
to include parts of both areas.
Unbroken expanses of tall grass seem not to be optimum habitat. The
crest of the hill at the Damm Farm (Pl. 17, Fig. 1) was an area of
more or less homogeneous grassy habitat. Turtles were seldom found on
the crest of the hill although this area was as thoroughly searched
for turtles as any other area. Known home ranges of nearly every
individual observed were on either one of the sides of the hill but
not on both sides.
At several places on the border of the pasture, turtles were able to
move freely into cultivated areas but seldom did so except for
nesting. Trailing records show that most of the turtles that entered
one of the cultivated areas returned again to the pasture.
Ornate box turtles seem to find places of shelter by trial and error
along regularly used routes of travel in their home ranges. The
individuals that I studied never returned to the same forms, and
seldom returned to the same natural burrows and dens. Probably
foraging, basking, and watering sites are found also by trial and
error.
Stickel (1950:375) placed considerable importance on the occurrence of
transient turtles in populations of _T. carolina_; in estimating
population density, she added to her study area a peripheral strip,
half as wide as the average, estimated home range, to account for
turtles that had home ranges only partly within the study area. The
study area used by Stickel had no natural boundaries, as habitat
conditions on all sides were essentially the same as those of the
study area itself. The pasture at the Damm Farm, on the contrary, is a
relatively isolated area of natural grassland, bordered by rock
fences and cultivated fields. I believe that most of the box turtles
found on the pasture were permanent residents there. Individual box
turtles at the Damm Farm seemingly occupied but one home range and it
did not change from year to year. Populations of _T. ornata_ in areas
less isolated than the Damm Farm, like the populations of _T.
carolina_ studied by Stickel (_loc. cit._), could be expected to have
a higher percentage of transient individuals and individuals with
multiple or changing home ranges. Henry S. Fitch told me that he
considered most of the individuals of _T. ornata_ that were captured
only once at the Reservation were transients.
Several females at the Damm Farm traveled long distances from their
home ranges to nest but other females nested within their known or
estimated home ranges. Seemingly a complex of environmental factors,
including soil texture, weather, availability of water, and possibly
the urge for random wandering in the breeding season, governs the
distances traveled by gravid females and the ultimate selection of a
satisfactory nesting site. Females, because of their more extensive
travels in the nesting season, seem more likely than males to have
multiple or changing home ranges. Males of _T. ornata_ did not
noticeably alter the extent or pattern of their movements in the
breeding season. Hibernacula, unlike nesting sites, were within the
known or estimated home ranges of all individuals studied.
[Illustration: FIG. 28. The movements of an adult (non-gravid)
female of _T. o. ornata_ in the house pond area at the Damm
Farm during a period of 24 days in July, 1955 (solid line), and
a period of three days (broken line) in July, 1956. Solid dots
represent the points where the turtle was found as her thread
trail was mapped; hollow symbols represent points of recapture
when no trailing thread was attached to the turtle.]
The actual home range of almost every individual studied, even
of those individuals for which the most data were available, probably
differed at least slightly from the observed or estimated home
range. One adult female, for example, was captured six times in
two years within a radius of approximately 50 feet. Another female
was found 2780 feet from her last point of capture. These last
two records were regarded as unusual; when they were grouped
with records of the 44 individuals mentioned above, the average
radius of home range for the entire group was much larger (327
feet).
[Illustration: FIG. 29. The movements of a gravid female of
_T. o. ornata_ in the southern ravine area at the Damm Farm in
a period of ten days in June, 1956. Her movements were, for the
most part, in and around several ravines (shown on map by
broken lines) where she was searching for a nesting site. For
explanation of symbols see legend for Fig. 28.]