Captive care and breeding of the Spotted Pond Turtle, Geoclemys hamiltoni |
Wayne Hill and David S. Lee, © 2007 Asian Turtle Consortium
The Spotted Pond Turtle, Geoclemys hamiltoni is a large (up to 36 cm) rare, aquatic turtle found in India, adjacent Nepal and Bangladesh, and extreme western Pakistan. Within these countries it is restricted to the Brahmaputra, Ganges and Indus drainage systems. The Nepal record is from the India-Nepal border and the turtle is probably only peripheral in the latter country. This species is also known as the Black Pond Turtle, the genus is represented by this single species, no subspecies are recognized and geographic variation has not been reported. Little information exists on the natural history of the species and most accounts are primarily taxonomic descriptions. There are only a few published notes by people who have worked with the species in the wild.
The turtle is nominally protected by legislation in all range countries. This is a Red List species of the IUCN (1996) and it is considered low risk-near threatened. It is listed as Endangered in Bangladesh by the 1999 Red Data Book. Spotted pond turtles are protected by Schedule I of the Indian Wildlife Protection Act of 1972 and by Schedule III of the Bangladesh Wildlife Protection Act of 1974. Populations seem to have benefited by the creation of several sanctuaries created in northern India, but over all the species is declining in both numbers and in over all distribution. Geoclemys is protected under the USFWS endangered species act and has been protected from export since July 1975 by CITES as an Appendix I species. The pet trade is not a conservation issue in the United States market but this turtle does appear in the pet trade in countries where CITES is not carefully enforced. They are eaten by Hindus and exported to the food markets in China from Bangladesh. In India some international trade exist but most are eaten locally. The species was fairly abundant through the early 20th century but it has now been depleted drastically throughout its range. The major conservation concerns are over exploitation of eggs and adults for food; habitat destruction; loss of nesting areas by commercial removal of sand; clearing of riparian and aquatic vegetation resulting in loss of cover for the turtles, food for aquatic snails, and soil erosion. The construction of hydro-electric dams and other barriers now restricts the movement of adults to nesting sites. Many of the conservation issues are the result of extensive river flood plain agriculture in the region.
This Batagur lives in rather clear shallow water of oxbow lakes and sloughs with abundant aquatic vegetation. Their highly domed shell suggest that this is not a turtle of swift currents so they probably do not inhabit the main channels of large rivers on a regular basis. While they are found in rivers this seems to occur during seasons when river flood plain ponds are dry and the rivers are themselves are low. In the more arid northern portion of their range ponds and rivers may completely dry up by the early summer. At such times the turtles migrate to wells dug in river-beds.
Here we report on the long-term captive breeding of this species as part of an on-going conservation effort for rare and endangered Asian turtles. Because of the turtles decline in the wild this species is an ideal candidate for captive breeding as a long-term conservation tool. Our adult turtles are being maintained in outside enclosures in central Florida. Five wild caught juveniles were acquired in 1971. An additional two sub adult founders were acquired in 1990. The current breeding-group consist of the original 7 founders, 26 turtles from a 1997 hatch which are now breeding adults and 4 turtles of a new blood line from a breeding loan. Offspring from the breeding group which are now sub adults and juveniles are also part of this collection (1998 24 individuals; 1999 31 individuals; 2000 51 individuals; 2001 67 individuals; 2002 53 individuals; and 2004 55 individuals. The eggs were not found in time to incubate them in 2003 so there were no young produced that year.) Reproductive output fell after 2004 when the breeding pond was frequented by bald eagles and ospreys. While these birds are predominately fish eaters, the eagles are notorious predators of turtles. The adult turtles were moved and only ten young were produced in 2005 and another ten in 2006. An additional 25 individuals produced by this breeding group are held by various members Asian Turtle Consortium (see below). This represents the largest and most significant successful captive breeding group of these turtles known. It also is the longest term, most consistent, and only multi-generation program in existence for this globally endangered species.
In the wild Spotted Pond Turtles are reported to feed primarily on snails. Wild caught turtles from Pakistan voided snail opercula and undigested algae. The alga is believed to be ingested incidentally. Another study showed Geoclemys to be feeding on the snails, Lemnaea and Gyruls, and dragonfly larvae. The large heads and cusps and ridges in the turtle’s mouths are probably adaptations for crushing snails. Their occurrence in quiet waters with abundant aquatic vegetation is probably related to the fact that this vegetation supports extensive snail populations. In captivity this species is reported to eat meat, fish, shrimp, and insects and it is not known to eat plant material. Captive animals in Florida are fed primarily on defrosted frozen whole fish and commercial fish chow. They feed while swimming at the surface on the fish that are suspended on clothespins and eat pellets floating on the surface. However, they also consume aquatic animals living in their ponds and tanks. Water hyacinths placed in the ponds and pools housing adult and sub adult Spotted Pond Turtles are gradually striped of their roots. It is assumed that this is a result of turtles gleaning aquatic invertebrates from submerged root systems of these plants and that the roots are not a food source per se. Captives in North Carolina showed a similar behavior and gradually over several months striped roots of water lettuce.
Geoclemys are reported to be crepuscular, and we see some evidence of this in our captive population. However, a few turtle heads can be seen throughout the day, they respond to food whenever they are fed, and during the cool months of fall and winter, whenever sunning sites are exposed to direct sun turtles bask in the heat of the day. Turtles maintained out doors are shy and hide from view when approached. January temperatures in Central Florida average about 63 F, and the number of frost days average less than 5 per year and occasionally there is a freeze. Adults maintained outdoors have survived water temperatures as low as 46 F with no problem. Young turtles are kept inside during the winter and not subjected to cool temperatures.
Captive Breeding:
Initially our adult turtles were housed outside in a circular pool with a 6-meter diameter containing about 1 meter of water. Floating aquatic vegetation and a few sunning logs were provided. A ramp leading to a covered, sand filed nesting box was attached to one side of the pool. Turtles were fed daily. In the summer of 2002 the adult turtles and two large f1s from the 1997 hatch were moved to a large fenced out door pond. An electric fence runs along the sides of the enclosure. The open pond encompasses about two-thirds of the 150 x 300 foot enclosure and averages about 4 feet in depth. Aquatic vegetation covers a small percentage of the total surface area, and Tilapia were introduced to the pond. The land portion of the enclosure is maintained in mowed grass with a few open sandy areas for nesting. The 28 f1s from the 1979 hatch were moved to the out door pond housing the seven founders in September of 2004. Hatchlings and juveniles are housed in large plastic tubs with each year class housed separately with the older groups living outdoors. All age classes are fed daily. Eggs are incubated in damp vermiculite in a walk- in temperature controlled incubation room. Each clutch is kept in a separate covered container. The turtles are not housed with other species of chelonians.
The breeding group discussed here mate in Florida in January and February as opportunity allows. Courtship includes males mounting and biting the back of the head females.
Summaries of literature suggest that nesting extends from May to October but the original sources for this statement are unclear. Das was told that nesting corresponding with the monsoon season, with laying both prior to and just after the monsoons in February and again in October. Courtship has been seen in February and March and five nests laid in April and May indicate that there is variation in the breeding season in different portions of the turtle’s range. The breeding group discussed here lays from 13 April through 7 June with the majority of the eggs produced in May.
With rare exception the Florida breeding group chooses the west bank of the pond to nest. The soil in the nest hole is first wet with body fluids from the laying female. The nest holes are as deep as the turtle can reach with the back legs, so they vary in depth with the size of the turtle. All observed nesting was from 4 pm to midnight.
Egg size is reported in literature at 41-45 x 25-37 mm (various sources). Information on the Florida group is as follows: Eleven eggs from a single clutch laid on 7 June 2004 measured 36-43 (38.5) x 21.0-23.0 (21.97) mm and weighed 9-15 (11.78) grams. The weight of the total clutch was 129.6 grams. Eggs from seven other 2004 clutches which had not hatched by 24 June when they were examined were all of similar sizes and weights. Eggs with weights that dropped below 10 grams failed to hatch. Adults are known to produce two to three clutches per year, although multiple clutches in our captive group are suspected but not confirmed. Clutch size is reported by several authors to be from 13-36 eggs. From our first successful reproduction in 1997 clutch size has increased each year as the turtles increased in size. Turtles laying clutches of 10-12 eggs in 1997 are now producing up to 23 eggs per clutch. As the founder stock increased in size and additional f1 offspring were added to the breeding group total annual egg production increased. In 2004 100 eggs were recovered from the nesting area.
Studies by others show incubation periods of 74 days and 32-48 days. At 82 F eggs from the captive group reported here hatch in 60-64 days. Hatching success for fertile clutches varied from 50-95%, and was typically above 80%.
The size of hatchlings is reported to be 35-37 mm. Information on the Florida group is as follows: Nineteen young from a single clutch were weighed and measured by us on the day of hatching (24 June 2004). Their lengths were consistent in size with what has been reported in the literature. Total carapace length ranged from to 34.6 to 38.5 (37.0) mm. Width ranged from 26.5 to 29.7 (28.7) mm and height was from 19.0 to 21.2 (20.2) mm. Weights ranged from 10 to 12.6 (11.89) grams. In overall appearance the young resemble adults in coloration, although they are move vividly marked. The interpreted keels are pronounced and the posterior marginals are more serrated than those of the adults.
Growth of our captive bred young was tracked by measuring samples of turtles of known age classes. Considerable variation occurred in the growth rates of all classes but individuals essentially doubled in size annually. Only a small sample of each age class was measured and weighed, this included the smallest, largest and two typical sized turtles from each class. Turtles could be reliably sexed by their fourth year and 4-7 year old males were up to 20-36% greater in mass than females of the same age. Sex ratios of captive hatched turtles were not studied but superficial and random examination indication that they were approximately even. Turtles hatched in 1997 reached breeding condition in 2004, thus in this year the founder stock, f1s and f2s are all represented in this captive breeding group. It is possible that a few of the 1997 f1s nested in 2003 and eggs were overlooked because of the shifting of housing. At any rate captive raised turtles reach sexual maturity and produce viable eggs within seven years. Size at first breeding is 216 to 250 mm and 1135 to 1515 (1385.4) grams. Standard carapace length increase averages about 28 mm a year and weight increase is about 198 grams/year during the first seven years needed to reach sexual maturity.
This breeding program reported here is but one of a number for rare and endangered Asian turtles under captive management by the Asian Turtle Constrain. This Consortium consists of about 100 active members all of which are in the private sector. These captive breeding groups serve as assurance colonies in case at some future date repatriation of various species is needed within their natural range. For many of these turtles little is known regarding their biology. So, in addition, various aspects of the natural history and captive husbandry of individual species are being learned and reported by Consortium members. Published in Reptiles 15(3); 34-41
Published information on G. hamiltoni:
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