Ornate box turtles were probably more numerous on the Damm Farm than
any other kinds of reptiles, excepting skinks (_Eumeces fasciatus_ and
_E. obsoletus_), and were by far the most conspicuous element of the
reptilian fauna.
The 194 box turtles that were marked at the Damm Farm were captured a
total of 437 times. Seventy-nine (41 per cent) individuals were
recaptured at least once, 49 (25 per cent) twice, 29 (15 per cent)
three times, and 20 (10 per cent) were recaptured at least four times.
Only three individuals were recaptured more than eight times. The
greatest number of recaptures for a single individual, an old female,
was 23.
In all, 185 turtles (95 per cent of total recorded at Damm Farm) were
captured on the pasture. Of these, 73 were in the northwest corner
area, 44 in the house pond area, and 35 in the southern ravine area.
The density of the population at the Damm Farm, considering the entire
area, was .88 turtles per acre; for the woodland area alone, density
was .41 turtles per acre and for the pasture alone, density was 1.49.
Acreage and population density in the northwest corner, house pond,
and southern ravine areas were respectively, 28 acres with 2.6 turtles
per acre, 7 acres with 6.3 turtles per acre, and, 17 acres with 2.6
turtles per acre. The densities noted above for the wooded area and
for the entire Damm Farm are low as a result of incomplete sampling in
the wooded area. Estimates of population density for the subdivisions
of the pasture seem more closely to approach the true population
density in areas of favorable habitat.
Fewer unmarked turtles were captured as the study progressed, but they
were still being captured occasionally when field work was terminated.
In order to estimate the number of turtles in the population at the
Damm Farm the "Lincoln Index" (Lincoln, 1930) was used to compare the
ratio of marked individuals to total number of individuals (17:56) in
collections for June, 1956, to the ratio of marked individuals as of
July 31, 1955 (87) to total individuals in the population; the result
was 286.
Fitch (1958:78) estimated the population of _T. ornata_ in one area of
the Reservation (including woodland and ungrazed pasture) to be .076
turtles per acre. Stickel (1950:373) estimated the population of adult
_T. carolina_ to be four to five turtles per acre in favorable habitat
at the Patuxent Research Refuge, Laurel, Maryland; juveniles comprised
less than ten per cent of the population.
Of the 194 turtles marked at the Damm Farm, 103 (53 per cent) were
adult or subadult females, 61 (31 per cent) were mature males, and 30
(16 per cent) were juveniles of undetermined sex. The ratio of males
to females was then, 1.00 to 1.69, and the ratio of juveniles to
adults was, 1.00 to 6.47. Eighteen of the 194 individuals were
juveniles less than 90 millimeters in plastral length and only six had
plastra less than 60 millimeters long (Fig. 25). The unbalanced ratio
between males and females may result, in part, from sexual differences
in habits. The studies of Carr (1952:9), Fitch (1954:140), Forbes
(1940:132), Legler (1954:138), and Risley (1933:690), have shown,
however, that unbalanced sex ratios, with females outnumbering males,
are found in several species of reptiles, especially in turtles.
Records for 540 adult _T. ornata_ collected at the Damm Farm, the
Reservation, and on roads in eastern Kansas, show that females
outnumber males just before and during the nesting season and again in
late autumn (Fig. 26). The high incidence of females in May, June, and
July, can be explained by their more extensive movements associated
with nesting in these months. I have no explanation for the increased
number of females captured in late autumn. In April and August, the
only two months in which males were more abundant than females, the
samples were small. The number of juveniles collected was too small to
allow any trustworthy conclusions concerning their seasonal incidence;
a few juveniles were taken in nearly all the periods in which adults
were active.
Risley (1933:690), studying _Sternotherus odoratus_ in Michigan, found
an over-all sex ratio of 1.0 male to 2.3 females; the percentage of
females in collections ranged from 50 to 71 per cent in April and most
of May and rose to 83 and 85 per cent in late May and mid-June,
respectively.
The infrequency with which hatchlings and small juveniles of ornate
box turtles are observed is well known to naturalists. Several of my
colleagues who are expert field observers and who have lived in areas
where ornate box turtles are abundant, have never seen hatchlings;
many other persons have seen only one or two. Rodeck (1949:33), noting
the abundance of coleopterous insects in the scats of captives and the
rarity of individuals of all age groups during dry periods in
Colorado, commented, "It is possible that the young are even more
subterranean than the adults. Perhaps they spend their early years in
rodent or other burrows where there is a fairly abundant insect fauna.
Increasing size might force them to the surface for feeding, with a
daily return to a burrow for resting and protection."
[Illustration: FIG. 25. Composition of the population of
_T. o. ornata_ at the Damm Farm based on the 194 individuals
marked there in the years 1954 to 1956. Individuals smaller
than 100 mm. ordinarily could not be sexed accurately and are
shown as open bars. Open bars in the groups larger than 100 mm.
are for females, whereas solid bars are for males.]
My own experience in the field has shown that small examples of _T.
ornata_ are not so rare as previous workers have believed. Small box
turtles occupy the same microhabitat as do the adults and seem not to
be more aquatic or subterranean in habits. Juveniles are found in
burrows, in marshy areas, and in other sheltered places, but so are
adults. Most of the juveniles that I found were in open situations
where adults were abundant, sometimes within several inches of a place
where an adult was feeding or basking. Nearly every one of the smaller
turtles was discovered when I was closely scrutinizing some other
object on the ground; sometimes juveniles were actually touched before
being seen. Most juveniles were covered with cow dung or mud and
blended so well with the substrate that they were detected only when
they moved. It is likely that only a small number of the young box
turtles present in an area is ever actually observed. Young are more
vulnerable to predation and injury because of their small size, soft
shells, and immovable plastra. They evidently rely, to a large extent,
on inconspicuousness for protection.
[Illustration: FIG. 26. The seasonal abundance of females of
_T. o. ornata_ based on 540 adults captured at the Damm Farm,
the Reservation, and on roads in eastern Kansas, in the years
1954 to 1956. Records are grouped in periods of 30 days, the
periods beginning with the dates shown at the bottoms of the
bars. Juveniles are not considered. Numbers at the top of each
bar indicate the size of the sample (both sexes) and give an
approximate indication of relative seasonal abundance of
adults, except for August, when little field work was done.]