Part 16

TABLE 6.--Kinds of Animals Found in the Stomachs of 25 Terrapene o. ornata of Both Sexes (23 adults, 2 juveniles) from Douglas County, Kansas. Frequency of Occurrence (number of stomachs in which found) is Given for Each Item Listed. =======================================+============================= | FREQUENCY OF OCCURRENCE |--------+-----------+-------- | Adults | Larvae | Total ---------------------------------------+--------+-----------+-------- Gastropoda | | | Helisoma sp | 1 | | 1 Succinia sp | 1 | | 1 Polygyra sp | 1 | | 1 Retinella sp | 1 | | 1 ---------------------------------------+--------+-----------+-------- Crustacea | | | Procambaris gracilis | 1 | | 1 Armadillidium vulgare | 4 | | 4 ---------------------------------------+--------+-----------+-------- Orthoptera (Locustidae) | | | Locustinae (Melanoplus | | | differentialis) | 13 | | 13 Oedipodinae | 1 | | 1 | | | Lepidoptera (unspecified) | | 1 | 1 Arctiidae | | 9 | 9 Noctuidae | | 10 | 10 Pyralidae | | 1 | 1 Sphingidae | | 1 | 1 | | | Diptera (Sarcophagidae) | | 1 | 1 | | | Coleoptera (unspecified) | 3 | | 3 Cantharidae | | 1 | 1 Carabidae (unspecified) | 6 | | 6 (Eumolops colossus) | 1 | | 1 Cerambycidae (Prionus fissicornis) | 1 | | 1 Chrysomelidae | | | (Diabotrica 12-punctata) | 1 | | 1 Curculionidae (Calendra parvulus) | 3 | | 3 Lampyridae (Photinus pyralis) | 2 | | 2 (Photuris sp.) | | 1 | 1 Phengodidae | | 1 | 1 Scarabaeidae | 11 | | 11 | | | Hymenoptera (Formicidae) | 2 | | 2 ---------------------------------------+--------+-----------+--------- Phalangida | 1 | | 1 | | | Araneida (Epeira) | 1 | | 1 | | | Diplopoda | 1 | | 1 ---------------------------------------+--------+-----------+--------- Vertebrata (carrion) | | | 4 ---------------------------------------+--------+-----------+---------

TABLE 7.--Occurrence of Insects, by Frequency and Volume, in Stomachs of 23 Terrapene ornata from Douglas County, Kansas. Relative Volume is Based on Total Amount of Food Material Present, Excluding Stones and Vegetable Material Contained in Dung. ===================+=========+=============+==============+========== | Insects | Orthoptera | Lepidoptera |Coleoptera | (all) | | (larvae) | -------------------+---------+-------------+--------------+---------- Average | | | | volumetric | | | | percentage | 88.6 | 28.7 | 26.9 | 32.5 -------------------+---------+-------------+--------------+---------- Range | | | | (volumetric | trace | | | percentage) | to 100 | 0 to 100 | 0 to 100 | 0 to 100 -------------------+---------+-------------+--------------+---------- Frequency of | | | | occurrence | | | | (percentage | 100 | 52 | 65 | 74 of total stomachs | | | | in which found) | | | | -------------------+---------+-------------+--------------+----------

Snails, sowbugs, and the one individual of crayfish found in stomachs were kinds that could be expected to occur in moist grassland or in wooded stream courses. Mulberries were present in one stomach and fragments of bird's-nest fungi (Cyathus striatus) were present in another. Carrion consisted of remains of mammals and birds; the only identifiable items were bones of the eastern cottontail (Sylvilagus floridanus) and a chicken. Stones up to seven millimeters in diameter were found in many stomachs; stones constituted as much as half of total stomach-contents. Presumably the stones were accidentally swallowed when food was taken from the ground.

The few adequate reports on dietary habits of T. carolina (Allard, 1935:325-326; Carr, 1952:147, 150, 152, 153; Stickel, 1950:361; Surface, 1908:175-177) indicate that the species is omnivorous but that individuals tend to be herbivorous or carnivorous at certain times. Ornate box turtles resemble T. carolina in being opportunistic feeders but rely on insects as a staple part of the diet. In this respect the ornate box turtle seems to differ from all other kinds of box turtles in the United States and it is probably unique in its habitual utilization of dung communities as a source of food.

POPULATIONS

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."

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.

MOVEMENTS

The only previous study of movements of T. ornata is that of Fitch (1958:99-101). He recovered 14 marked T. ornata at the Reservation a total of 30 times, the period between recaptures varying from one to seven years. He reported that the average radius of home range was 274 feet (for an area of approximately 5.4 acres), excluding a single (presumably gravid) female that moved 1830 feet in 53 days.

Although published information on T. ornata is scant, a considerable amount of information is available concerning its congener, T. carolina. The classic studies of Stickel (1950) on it constitute the most complete account of populations and movements for any reptile or amphibian, and probably, for any vertebrate. She found the average home range of adults to be 350 feet in diameter. Home ranges were not defended as territories and nearly all individuals were socially tolerant of one another. Movements (studied by means of a thread-trailing device) were characterized by frequent travel over the same routes within the home range. Some turtles concentrated their activities in only one part of the home range, moving subsequently to another part, and some turtles had two ranges between which they traveled at varying intervals. Females ordinarily left their home ranges to nest.

Other noteworthy, but less detailed, studies of populations of T. Carolina are those of Breder (1927) who found evidence of home range and homing behavior, and of Nichols (1939b) who, after observing a marked population on Long Island over a period of twenty years, found evidence of homing behavior and estimated normal home range to be approximately 250 yards in diameter. Numerous shorter papers such as those of Schneck (1886) and Medsger (1919) document the tendency of T. carolina to remain in restricted areas over long periods.

Important studies that indicate the presence of home range and homing behavior in other chelonians are those of Cagle (1944) on Pseudemys scripta and Chrysemys picta, and of Woodbury and Hardy (1948) on Gopherus agassizi. Grant (1936) and Bogert (1937) have also indicated that movements of individuals of Gopherus agassizi are restricted to limited areas.

Locomotion

Ornate box turtles moving forward over even terrain hold the plastron a quarter to a half inch above the ground and keep the head and neck lowered and extended. Each foreleg is brought forward and the humerus points nearly straight ahead when the foot touches the ground. Nearly all of the palmar surface is initially in contact with the ground but as the body is brought forward and the humerus swings outward, only the claws, and finally, only the two inner claws are in contact with the ground. Of the hind feet, the medial surfaces are the principal parts that touch the ground but some traction is derived from the hind claws at the beginning of each cycle of the hind leg. Under normal conditions, box turtles move slowly and pause to rest and examine their surroundings every few feet. When resting, the plastron is in contact with the ground, the legs relaxed, and the head and neck are extended upward. Some turtles seeking shelter from the heat of sunshine walk rapidly for a hundred feet or more without pausing.

Turtles seen feeding under natural conditions displayed remarkable agility in making lunges, consisting of one or two short steps and a thrust of the head, at moving objects. Turtles kept in my home were able, after being conditioned to hand-feeding, quickly to intercept a grape rolled slowly across a linoleum-covered floor.

Frederick R. Gehlbach told me that, of several species of captive turtles observed by him, T. ornata characteristically walked with the plastron held well above the substrate, as did Gopherus berlandieri, but that T. carolina (specimens from the northeastern U. S.) dragged their shells as they walked. Apparently T. carolina in Kansas (currently referred to the subspecies triunguis) differs somewhat in gait from populations in the eastern part of the range; several individuals of T. carolina from Kansas that I observed in captivity, kept their plastra raised well above the smooth, hard substrate over which they walked.

Box turtles at the Damm Farm were able easily to climb ravine banks that sloped at an angle of 45 degrees and, with some difficulty, could climb banks as steep as 65 degrees. Most individuals, however, were reluctant to walk directly downward on banks as steep as 45 degrees. Several individuals were seen to lose footing when climbing up or down a steep bank and to roll or slide to the bottom. Ordinarily, T. ornata is able to climb over a sheer surface as high as its shell is long, provided the surface is rough enough to give some traction to the foreclaws. The claws of first one, then the other forefoot are placed over the top of the barrier and then a hind foot, extended as far forward as possible, secures a hold as the turtle goes over the barrier.

A number of observations on speed were made in the field where distance traveled and time elapsed were known approximately. Speeds ranged from 20 to 100 feet per hour in the course of foraging. Higher speeds (400 or more feet in one hour) were for turtles moving along pathways or seeking shelter. Gould (1957:346) observed somewhat faster speeds in T. carolina (192 feet per hour in cloudy weather and 348 feet per hour in sunny weather); he observed individuals that had been removed from their normal home ranges.

Individuals of T. ornata that were placed in water swam moderately well but were clumsy in comparison to individuals of more aquatic emyids such as Pseudemys and Chrysemys. Box turtles were never observed to swim voluntarily, although they were frequently found in shallow water. On several occasions I confronted individuals at the edge of a pond so that the only unblocked route for their escape was through deeper water; nearly always these individuals attempted to crawl past me, to crawl away in shallow water parallel to the shore, or to hide in soft mud at the edge of the water. Box turtles floated high in the water with the dorsal side upward and had little difficulty in righting themselves when turned over. The head and neck are extended and submerged when the turtle is swimming; forward progress is interrupted every few moments to elevate the head, presumably for purposes of breathing and orientation. The shell is never submerged. The swimming of T. ornata is in general like that of Pseudemys or Chrysemys that have become dehydrated after long periods out of water and cannot submerge. These more aquatic turtles, however, quickly overcome their bouyancy, whereas examples of T. ornata, even if left in water for several days, are unable to submerge. Clarke (1950) saw an ornate box turtle swim a 60-foot-wide stream in Osage County, Kansas; his description of swimming agrees with that given above.

The meager swimming ability of T. ornata is of apparent survival value under unusual conditions and enables T. ornata to traverse bodies of water that would act as geographic barriers to completely terrestrial reptiles; however, swimming is a mode of locomotion seldom used under ordinary circumstances.