The family Emydidae is comprised of many chelonian species that are immensely popular among zoos, private breeders, and turtle enthusiasts. Almost every young person has kept a box turtle at some point in their lives, but the most popular group, undoubtedly, must be the pond turtles of the genus Clemmys. The eastern forms, especially, have that winning combination of beauty and rarity that places them in demand the world over, as is evidenced by the increased numbers on reptile dealers' price lists.
The largely terrestrial wood turtle, Clemmys insculpta, is the largest member of the group and is found in unpolluted streams with sandy bottoms from southern Canada to northern Virginia, and as far west as southeastern Minnesota. The prettiest and most aquatic member is the spotted turtle, Clemmys guttata which ranges from southern Maine west to extreme northeastern Illinois and south along the coastal plain to northern Florida. Last, but not least, the bog turtle, Clemmys muhlenbergii, is not only the smallest of the group, but the rarest as well and occurs in disjunct populations from eastern New York and western Massachusetts south through the Appalachian Mountains into northeastern Georgia. A large gap separates the northern and southern populations between northern Maryland and southwestern Virginia.
According to Slavens (1989), twenty-nine zoos and private breeders maintain C. insculpta, twenty-eight reported keeping C. guttata, only twelve maintain C. muhlenbergii, while only five zoos and breeders reported working with all three species in their collections. The bog turtle appears in fewer collections because of its protected status in much of its range and the high probability that many may have been illegally obtained, therefore the private sector is reluctant to report any involvement with the species. Most of the bog turtles presently kept by zoos are either grandfathered or those obtained under state permits for captive breeding and headstart purposes (Herman, 1987a; Tryon, 1988, 1990).
Zoo Atlanta has maintained the eastern Clemmys periodically since 1965-66 (Herman, 1989b). The first wood turtles were obtained by the zoo in September, 1965 followed shortly by spotted turtles and bog turtles in July, 1966. Two spotted turtles and two bog turtles were reported on the zoo's October, 1967 inventory, but no information was included. Zoo Atlanta did not keep either C. guttata or C. insculpta for nearly ten years until two pairs of spotted turtles were purchased in 1978. Wood turtles were added to the collection after a seventeen year hiatus when two pairs were obtained on breeding loan and/or donated. One pair of bog turtles were purchased in 1967 and are still maintained in the collection along with other C. muhlenbergii from captive breeding and/or studies conducted with various state's permission (Herman, 1989). Our techniques for captive husbandry are actually variations on those used elsewhere, with some slight modifications thrown in.
Management of Adults
The adult groups of Clemmys are housed in individual artificial bogs that were constructed to closely resemble their natural habitats. Each species' individual set-ups are:
Wood Turtle. The enclosure that houses our 2.2 wood turtles measures approximately 760 x 250 cm (25 x 8 ft.) and a sunken 950 l (250 gal) metal stock tank provides an area for swimming, mating, and brumation. A flow of freshwater trickles into one end of the tank and exits through an overflow at the opposite end creating a flowing stream effect. The turtles are able to burrow into the mud and gravel substrate to escape sub-freezing temperatures. A variety of berry-producing plants and weeds provide cover and the perimeter fence has an overhang to prevent escape by climbing, at which wood turtles are adept.
Spotted Turtle. Our 1.4 spotted turtles are kept in a 180 cm diameter (6 ft.) metal stock tank buried to a depth of 48 cm (18 in) for insulation. This set-up is almost identical to those of the bog turtles and will be discussed in more detail in that section.
Bog Turtles. The bog turtles (4.5) are housed in various sized metal or fiberglass tanks. Following are the number of bog turtles per enclosure and the dimensions of the enclosure: 1.1 (1967 pair) are housed in a 180 cm diameter (6 ft.) metal stock tank, 1.2 (North Carolina turtles) are housed in a 200 cm diameter (7 ft.) metal stock tank, 1.1 (Virginia turtles) are housed in a 120 x 120 x 60 cm high (4 x 4 x 2 ft.) fiberglass tank, and 1.1 (progeny of 1967 pair) are housed in a 100 x 120 x 60 cm high (3.5 x 4 x 2 ft.) fiberglass tank.
The same basic design is used in the construction of each bog no matter the size or shape. Plumbing is achieved using 1/2 inch PVC tubing with freshwater supplied from the tap. An overflow drain is installed in each bog and the water exits into the zoo's sewer system so that a completely open system is maintained. Turn-valves at the intakes are used to regulate water flow. Substrate in each tank consists of a 5 cm layer of pea gravel topped by a 10 to 15 cm layer of peat and sphagnum moss mixture. The water level is maintained 5 to 8 cm above this peat mud layer. Long fiber sphagnum moss is the cement used to build up the land area which also contains ground peat and sand over the gravel base. Landscaping is achieved by the use of live plants, such as, sphagnum mosses, sedges, bog rushes, ferns, and other wetland species. Two rivulets in each of the larger bogs flow from the intake through the land area into the water area. One-third of the set-up is comprised by the water area. Sheet metal overhangs on the corners of the rectangular tanks prevent escape by climbing.
Management of each bog consists of selective cutting periodically through the year and burning off dead vegetation in February. This practice keeps the weedy plants and shrubs from choking out the bogs and rejuvenates them.
Feeding regimes differ slightly among the three species. Since the adults live outdoors throughout the year, they forage for and feed on a variety of invertebrates and plants. Salads are fed biweekly to the wood turtles. Each salad consists of chopped fruits, vegetables, greens, and chopped skinned mice. Pervinal multivitamin powder (St. Aubrey/Division of 8-in-1 Pet Products, Inc., New York, NY) may be added occasionally, or as needed, to the salad. The spotted turtles and bog turtles are supplemented with either newborn mice, crickets dusted with bone meal, or earthworms three to four times weekly. The bog turtles have been observed feeding on the leaves of grass-of-Parnassus and dayflowers that grow in the enclosures.
The outdoor bogs make it easier to observe natural behaviors since the turtles are not frequently manipulated as is the case for indoor exhibits. Each turtle is located during brumation so that periodic monitoring can be done. Most of the observed behaviors parallel, for the most part, those seen in nature. Seasonal temperatures have been recorded periodically since the first bog was constructed in 1979. Environmental temperatures (air, water, and substrate) were recorded daily in one bog set-up between November, 1982 and March, 1983: air, -4 to 18° C; water, 6 to 15° C; substrate, 4 to 14° C. Extreme fluctuations in temperature are expected in Atlanta because of the variable winter weather that occurs each year.
The wood turtles essentially do not experience the brumation periods that they would in more northern climes and become inactive only on the coldest days. They are often observed basking on sunny days in January and February. The spotted turtles become less active in November and December and observed basking in late January, with increased surface activity during February and March. The bog turtles, on the other hand, seem to disappear during October or November with little or no surface activity observed until mid February. By the end of March most of the C. muhlenbergii are actively seen basking and foraging for food. This activity is four to six weeks earlier than that observed for wild turtles in North Carolina (Herman, 1986a).
Wood turtles have been successfully bred by several zoos and private breeders (Slavens, 1985). Zoo Atlanta has maintained at least 2.2 wood turtles since 1983-84. Combat leading to courtship has been observed each year, with copulation observed in October, November, and March. Nesting was observed on 21 April 1990 for the first time and photographs of the complete nesting process were taken. This is the earliest date for egg deposition that we have recorded here. An average clutch of 6.3 eggs is usually deposited by our wood turtles. Since 1985, a total of 19 eggs (3 clutches) have been deposited and the following data were recorded:
The eggs were incubated in either small aquaria or plastic boxes in a medium of peat moss and sand or long fiber sphagnum moss at a temperature of 26.7-27.8° C. We successfully hatched wood turtles in 1987, 1988, and 1990. Incubation periods have ranged from 51-54 days. Carapace lengths of ten neonate wood turtles that hatched since 1987 were:
|Range:||26.2-35.4 mm||x=32.3 mm|
Spotted turtles have also been bred in several zoos and private collections (Paul et al., 1983; Slavens, 1985). A group of C. guttata (2.3) was purchased by the zoo in 1978, the first since 1968. Copulation was observed shortly after their introduction into the outdoor bog. Nesting was observed only once, although nests containing from 1 to 4 eggs have been found annually. The eggs were usually left in the nest to incubate under natural conditions and proved successful. Unfortunately, the imported red fire ant (Solenopsis invicta) invaded the nests in 1985 and predation on recently pipped eggs was observed. Now, as soon as nests are located, the eggs are removed and incubated indoors. Measurements and masses of three C. guttata eggs deposited since 1985 were:
The spotted turtle eggs were incubated under similar conditions to the wood turtle eggs at temperatures ranging from 26.0-28.9° C. Incubation periods ranged from 44-63 days. Carapace lengths of neonate spotted turtles (n=7) hatched since 1984 were:
|Range:||26.8-30.3 mm||x=28.7 mm|
Bog turtles were first bred in captivity at the Bronx Zoo in 1973 (Anon., 1974). Since then they have bred at other zoos (Bowler, 1974; Tryon and Hulsey, 1977; Herman 1980; Herman and George, 1986; Reininger, 1990; Tryon 1990) and in private collections (Warner, 1974; Bartlett, 1990). One pair (1.1) of bog turtles was purchased by the zoo in 1967 and is still reproductively active. These turtles have surpassed the longevity record reported by Bowler (1977) and are at least 35 years old. Offspring have been hatched from their eggs annually since 1975. During this time, this one female has deposited a total of 58 eggs of which 28 have successfully hatched. Her clutches have ranged from 2 to 6 eggs (mean, 3.4 eggs per clutch) and she deposited multiple clutches in 1985 (Herman, 1983, 1986c). Offspring from this female produced the zoo's first successful second generation hatching of bog turtles in July 1990 (Archibald, 1990).