Captive Husbandry of the
Eastern Clemmys Group at Zoo Atlanta
by Dennis W. Herman
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
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:
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).
A second pair (from North Carolina) has been used in another breeding project and they have produced a total of 12 eggs
since 1984 (mean, 2.4 eggs per clutch) of which only four successfully hatched. Initially, all bog turtle eggs located
in the outdoor bogs were left in the nest for natural incubation. Predation from an opossum and fire ants took their
toll in 1985-86 (Herman, 1986b, 1987b) and now all bog turtle eggs are incubated indoors in plastic sweater boxes or
small aquaria. Incubating medium consists of peat moss and sand or long fiber sphagnum moss and the incubation
temperatures range from 24-32° C. Neonates emerge after an incubation period of 42-56 days. Measurements and masses of
34 bog turtle eggs produced since 1985 were:
Carapace lengths of 27 neonate bog turtles captive- hatched at the zoo since 1983 were:
After many years of producing neonate Clemmys one might expect a few aberrancies or abnormalities to show
up. Shell anomalies are common with divided vertebral scutes or additional marginal scutes the most prevalent. In 1986
twin bog turtles were found in an egg among a clutch that was destroyed by fire ants. The fully developed neonates
were dead, but in great shape (Herman, 1987b). Color aberrancies are the least common abnormalities observed. A
leucistic neonate bog turtle was found in an egg that failed to hatch, but appeared to be full-term, in 1988. A dead
leucistic spotted turtle was found in a recently pipped egg in July, 1990 (Herman, in preparation).
Captive Management of Neonates
Neonates of the three eastern Clemmys are generally reared together in an aquarium that measures 122 x 60 x 30 cm high. The rearing set-up is very similar to the larger outdoor bogs, although filtration is achieved with an
undergravel filter. This filter is covered with a coarse layer of pea gravel that is in turn covered with a peat mud
layer. The peat mud layer is created, as in the larger set-ups, by floating ground peat moss on the water until it
sinks to the bottom. A period of 3-4 weeks is usually needed for this to take place, but the filtering action of the
undergravel unit facilitates the sinking. Excess peat is skimmed from the surface. A land area is built up at one end
of the set-up and landscaped with live bog plants, i.e., sphagnum mosses, sedges, and rushes. Lighting is provided by
four 40W Vita-Lites (Duro-Test Corp., North Bergen, NJ) that are placed 30 cm above the land surface. Basking spots
are heated by three 150W incandescent plant lights. Since ultraviolet light is essential for neonate turtles, this
requirement is met using a 250W/110V UV lamp on a timer. No more than five minutes of UV per day is used. Freshwater
is added to the set-up as needed due to evaporation. An overflow drain is used to periodically flush the set-up.
Humidity is another important factor in rearing neonate Clemmys, especially C. muhlenbergii. Zovickian
(1971) found humidity essential to the proper growth in C. muhlenbergii neonates, therefore our rearing bog
provides moderate to high humidity for the neonates.
Feeding and Growth
A calcium-enriched diet is fed to the neonates 2-3 times weekly. This diet includes Frog or Turtle Brittle (NASCO,
Fort Atkinson, WI), earthworms, chopped mice or newborn mice, dusted crickets, slugs, and various other invertebrates.
The smaller sized Frog Brittle is fed to small neonates and Turtle Brittle to the larger neonates and juveniles.
Currently, Turtle Brittle constitutes 50-60% of the normal diets fed to our neonate Clemmys. The following is
an example at Zoo Atlanta (actual feeding period is 10 months because neonates usually refuse food until 2 months of
The above feeding record was an actual feeding record for a group of 4 neonate C. muhlenbergii over 40 weeks
(1.45 feedings per week). Earthworms and/or dusted crickets are used as the first meals to stimulate the neonates into
eating. It seems that they are attracted to the movement of these food items. When a good feeding response is
observed, then Turtle Brittle is alternately offered until accepted. Once acceptance takes place, Turtle Brittle
becomes the preferred food item.
Growth rates of neonate Clemmys are usually kept for at least the first year, except for C. muhlenbergii,
which are studied in more depth at the zoo. See Table 1 for a comparison of the mean growth of the three species over
a one year period.
Neonates are usually fed throughout the winter months and do not experience brumation as the adults. As can be seen
from Table 1, the wood turtles exhibit faster growth rates than those of the spotted turtles or bog turtles. The
growth rates for the bog turtles now approximate those of neonates that have been found in nature (Herman, pers.
observation.). In earlier years bog turtle growth was accelerated and the results were year old turtles with a size
equivalent to a 3-4 year old wild caught C. muhlenbergii. I personally do not believe in producing misshapen
"mega-turtles" so neonates are fed less and a more natural rate of growth is achieved. Arndt (1972) maintained two
hatchlings which grew an average of 3 mm during four months. Sachsse (1974) reported a growth rate of 13.5 mm over a
six month period for one hatchling, while Warner (1974) recorded growth in two neonates at 4 mm each in one month.
Tryon and Hulsey (1977) recorded 33 mm mean growth in two neonates over a 12 month period at Fort Worth Zoo. The mean
growth of C. muhlenbergii presented in Table 1 falls within the range of that reported by the above observers.
Populations of eastern Clemmys are declining because of habitat destruction and commercial exploitation
(legal or illegal) for the pet trade. Captive breeding programs can be beneficial in eliminating the illegal trade and
filling the demand for these highly sought-after chelonians. Knowledge gained from studying these interesting turtles
can help in captive, as well as, wild management of the species. It is important for zoo and private turtle breeders
to work more closely with state nongame wildlife agencies and to get actively involved in the conservation of the
eastern Clemmys. One can start by not purchasing turtles from questionable sources or where the legal origin
can not be determined. We can only hope that any involvement concerning the conservation of the eastern Clemmys
will be positive and beneficial--not only for captive populations, but for natural, wild populations as well.
I thank the staff of the Department of Herpetology for their assistance and encouragement. I am grateful to Howard
Hunt for his helpful suggestions and advice throughout the project. Captive breeding and possession permits were
kindly issued by the North Carolina Wildlife Resources Commission.
Anonymous. 1974. Rare bog turtles breeding at the Bronx Zoo. Def. Wildlife News 49(1): 64.
Archibald, E. 1990. Second generation bog turtles hatch. AAZPA Communique 9: 23.
Arndt, R. G. 1972. Additional records for Clemmys muhlenbergi in Delaware, with notes on reproduction. Bull.
Maryland Herpetol. Soc. 8(1): 1-5.
Bartlett, R. D. 1990. The bog turtle Clemmys muhlenbergi. Vivarium 2(3): 25-27.
Bowler, J. K. 1974. Breeding report. Chelonia 1(1): 9.
Bowler, J. K. 1977. Longevity of reptiles and amphibians in North American collections. SSAR Misc. Publ. 6: 32.
Herman, D. W. 1980. Atlanta Zoo hatches rare bog turtles. AAZK Anim. Keeper's Forum. 7(9): 198.
Herman, D. W. 1983. Life history notes: Clemmys muhlenbergi. Reproduction. Herpetol. Rev. 14(4): 122.
Herman, D. W. 1986a. Herp-of-the-Month: Clemmys muhlenbergii (Schoepff) bog turtle. North Carolina Herpetol.
Soc. Newsletter 9(2): 3-5.
Herman, D. W. 1986b. Life history notes: Clemmys muhlenbergi. Nest predation. Herpetol. Rev. 17(1): 24.
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Herpetol. Soc. 23(3): 122-124.
Herman, D. W. 1989a. Captive management and conservation of the bog turtle at Zoo Atlanta. pp. 597-600. In: AAZPA
Southern Regional Conference Proceedings. Atlanta, Georgia.
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muhlenbergii. pp. 39-45. In: M. J. Rosenberg (ed.). Proc. 12th International Herpetol. Symp. Captive Propagation
and Husbandry, Thurmont, Maryland.
Herman, D. W. and George, G. A. 1986. Research, husbandry, and propagation of the bog turtle Clemmys muhlenbergii
(Schoepff) at the Atlanta Zoo. In: S. McKeown, et al. (eds.). Proc. 9th International Herpetol. Symp. Captive
Propagation and Husbandry, Thurmont, Maryland.
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Occas. Pap. 12: 10-11.
Reininger, K. 1990. New York endangered turtles hatch at Burnet Park Zoo. AAZPA Communique 5: 21.
Sachsse, W. 1974. Zum Fortflanzungswerhalten Von Clemmys muhlenbergi Bel Weltgehender Nachamung Der
naturalichen lebensbedingungen Im Terrarium (Testudines, Emydidae). Salamandra 10(1): 1-14.
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Tryon, B. W. 1988. The rare little bog turtle of East Tennessee. Tennessee Wildlife 11(4): 6-9.
Tryon, B. W. 1990. Down in the bogs. Zoo Life 1(2): 38-43.
Tryon, B. W. and Hulsey, T. G. 1977. Breeding and rearing the bog turtle Clemmys muhlenbergii at the Fort Worth
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From: Proceedings First International Symposium on Turtles & Tortoises: Conservation & Captive Husbandry. pp. 54-62, 1991.