Care and Captive Breeding of the Highly Endangered Vietnam Pond Turtle

 Dennis Uhrig and David S. Lee
Asian Turtle Consortium

The Vietnam Pond Turtle, Mauremys (Annamemys) annamensis, is endemic to the central coastal lowlands of Vietnam. The only documented locality for this turtle is from Phun-Son in 1941, an area southwest of Da Nang. As far as we know there is no published information on this species in the wild, and it is not clear if any biologists have ever personally encountered this species outside of captivity. Ernst and Barbour (1989) note that its behavior in the wild is unknown. Published information seems to be limited to species descriptions, taxonomic uncertainty regarding the validity of the genus Annamemys and this turtle's relationship to other Asian Batagurs.

Hendrie (2000) states the species is known only from the food market trade in a few Provinces and that its habitat is believed to be marshes, streams and ponds. The basis for this and similar published habitat descriptions is unclear. Based on information from markets and available habitat this turtle's former range probably included an area from Na Trang to Hue. Documentation of the numbers that found their way into the food market trade has been limited as the species was generally unknown to enforcement agencies. Between 1994 and 2000 modest numbers of turtles were channeled into the pet trade, typically packed in with other species.

Here we provide species descriptions and information on the species' conservation status and outline the behavior and husbandry of two successful captive breeding groups of Vietnam Pond Turtles housed in the eastern United States. One of is maintained outdoors year-round in Florida and one in North Carolina that is kept inside during the winter months. The focus of our private sector efforts is the long-term conservation of these species through the Asian Turtle Consortium.

Description: Uniform dark brown to black, with a low, slightly arched carapace bearing three longitudinal keels. The medial vertebral keel is best developed in adults. Plastron is yellow with large black blotches on each scute and upon the underside of each marginal. A black band crosses the bridge. The head is pointed and dark brown with three lateral stripes running along each side. Lower jaw is yellow, and the upper jaw notched. Neck is long and dark dorsally. Toes fully webbed. Adults are up to 20 cm (10 inches) in carapace length. Compared to females males have longer and thicker tails and slightly concaved plastrons.

Conservation Status: Originally appeared on the 1994 Red List but was delisted for a time. The 1996 Red List placed the species at low risk, or least concern. Since the 1996 listing the species was proposed for Critically Endangered status and elevated five categories. The species is now listed as extremely scarce and highly endangered (vanDijk et al., 2000). The reasons stated for decline are habitat loss and collection for food and pet markets. The relatively small area where this endemic turtle once occurred is prime for rice production and is currently being converted to agriculture at a rapid pace. It should also be recognized that the region around Hanoi where these turtles occur was hit heavily with Napalm and Agent Orange during the Vietnam War. Many now consider this turtle to be functionally extinct in the wild. Vietnam currently allows no trade in any turtles, and M. annamensis is now listed by CITES. Vietnam signed onto CITES in 1994 but enforcement of National Wildlife Protection laws is at best marginal and inconsistent. Commerce and trade is typically permitted and enforced at the provincial level. In summary this species has not been seen in the food or pet trade in the last 5 years and it is likely
to be extinct in the wild.

Overview of Husbandry: The housing of the group in southeastern North Carolina is seasonal. During the winter they inhabit three interconnected pools (190-380 liters; 50 to 100 gallons in size) within a greenhouse. From late April through early October they are housed in an outdoor pen that contains two 380 liter (100-gallon) plastic pools. While the indoor and outdoor pools have ledges they are steep sided. Turtles can exit the pools by climbing up lightweight rubber doormats draped over the pool's edge. Floating aquatic plants provide both shade and browse for the turtles. Along with pools? filters the plants are helpful in the removal of nitrates. The outdoor pen is approximately 3.6 by 7.3 m  (12 by 24 feet) with about 70% of the enclosure being land; the greenhouse pen is 1.8 by 7.3 m (6 by 24 feet) with about 45% being land.

The other group, kept near Orlando, Florida, stays outside throughout the year. They are housed in a pen 4.8 by 7.3 m (16 x 24 feet). Centered in the pen is a pool 4.3 by 4.8 m (14 x 16 feet) with a maximum depth is 1.7 m (2.5 feet). While it has not been observed as a problem in the North Carolina pools and three sides of the Florida
pools are sloped so that the males cannot drown the females when mating. During the summer the pond is shaded with 60% shade cloth, and in the winter when temperatures fall below 4.4 C (40 F) well water is run through the pond. Ground water temperatures are about 22 C (72 F).

These turtles are successfully housed with other species. We both keep Chinese striped-necked turtles, Ocadia sinensis, with our M. annamensis. In North Carolina when kept indoors in the greenhouse their pools are also co-inhabited with Malayan box turtles, Cuora amboinensis, and four-eyed turtles. In summer, when outdoors, they live in pools along with Japanese pond turtles, M. japonica, Reeve's turtles, Chinemys reevesii, and four-eyed turtles, Sacalia bealei and quadriocellata. A hybrid male M. mutica x annamensis also lives with this group. While this hybrid has been seen trying to mate with a female M. japonica, it seems to pay no attention to the M. annamensis. Young from female annamensis to date have shown no sign of being hybrids.

Feeding; We feed our adults and young primarily on commercially available fish pellets, however, these turtles are omnivorous and will eat almost anything. Secondary foods for our captive groups include aquatic vegetation, fruits, vegetables, and various store produce greens (dark green varieties of lettuce, collards, kale, turnip greens, etc.). Like many aquatic Asian pond turtles juveniles and adults feed both on land and in water. They eat aquatic vegetation in such quantities that it is difficult to maintain submerged and floating vegetation in their pools. Large plants become stunted and eventually die while small species such as the various duckweeds (Lemna) are gradually eliminated from the pools. These turtles are fed two times a week in winter and three times a week during the warmer months. Hatchlings maintained in aquaria are fed three to four times a week in amounts that can be entirely consumed within 5 minutes. Both captive young and adults paddle frantically at the surface during feeding at night while adults fed during the day are secretive, remaining well-submerged and taking maximum advantage of aquatic vegetation and other cover. M. annamensis feed both day and night, but they forage more vigorously after dark. Lights over their outdoor pools attract various insects, many of which fall into the water and are consumed. Dragonfly larvae small frogs, Rana and Hyla, and other aquatic creatures that find their way into both greenhouse pools and outdoor ones are probably a significant part of their diet. Adults have been seen eating recently transformed leopard frogs, Rana utricularia that commonly occur in the outdoor pools in late summer and early fall. On several occasions they have been seen at night stalking and capturing them on land. As of now, iridovirus has not appeared in our local amphibian population but it will be interesting to see if this disease impacts how turtle collections are kept outdoors in the States should it spread regionally.

Other Behaviors: Vietnam pond turtles appear to be generalists, probably filling niches similar to Trachemys in North America, if true it is difficult to explain their restricted geographic distribution. These turtles are tolerant of extreme water temperatures ranging from the low of 6 C to high of 30 C (40s-80s F). They feed and exhibit activity in water ranging from 10 C (50 F) to at least 29 C (85 F). These Mauremys are extremely shy and are essentially never seen during the day except when being fed. They remain submerged and effectively use logs and aquatic vegetation as cover when near the surface.

Vietnam pond turtles are nocturnal. They will eat during the day when fed but otherwise most of the adults activity takes place after dark. At night they are seen foraging on aquatic vegetation, swimming at the surface and emerging to walk about on land. When practical we feed these turtles at night as we suspect this gives them a competitive advantage over the other species that share their enclosures.

While basking is occasionally observed in young individuals, the adults never bask. This is based on, literally, thousands of observations of their enclosures at all seasons and during random periods throughout the day.

Medical: This turtle does not seem as delicate as some other Asian species and no particular specific medical protocols appear necessary. When kept in cool water or under less than ideal lighting conditions both the young and adults are very susceptible to skin fungus. The white fungus grows mostly on necks and front limbs but is easily cured and for us has never been fatal. Keeping the water acidic helps prevent the fungus, so pools and aquaria housing this species will benefit from the addition of submerged pieces of cypress or hardwood.

Reproduction: We have observed mating in late August, and early September but based on fresh neck scars on our captives it occurs during other seasons as well. Copulation occurs in water at dusk and at night. Males lock their rear legs? claws under the posterior marginals of the female and their front legs under the marginals anterior to her front legs while simultaneously biting the top of her neck. Once he has a good grip he holds his head down and sideways and locks his jaws lock onto her neck. The swimming motions of the female moves the pair about, mostly near the surface, as she attempts to breathe. The act of mating is rather violent and the pair can be heard bumping into the sides of pools and submerged logs and when thrashing at and near the surface.

In captivity M. annamensis is a species with a protracted nesting period. We have records of nesting as early as mid March (in greenhouse setting) through early August. Most nesting occurs from late May through early July. Late nesting is associated with dry springs and early summers. Mean laying date taken over a six-year period for turtles housed outside in Florida is 20 June.  Individuals will double clutch. Fertile eggs band within a few days after laying.

Nesting occurs both day and night, but primarily at night. Nesting events last for several hours with considerable time spent repacking the nest. In digging the nest females moisten the soil with bladder discharge and then move the posterior portion of their shell left and right as they alternate legs while scooping out the hole. This leaves a telltale semi-circular rim of moist soil just behind the nest site that makes nests easy to locate. The group maintained in Florida always laid their eggs at the base of a saw palmetto, Serenoa repens, making nest location predictable. Eggs are deposited in nest holes that are 50 to 100 mm in depth. Each egg is positioned with the hind feet after being deposited. Soil above the egg chamber is packed tightly by the female who actually pounds the soil with the posterior quarter of her plastron after each scoop of soil is placed back in the hole. Clutch size ranges from 1-12 (6.3) eggs (n= 50).

Eggs: Wt. 10-15 (11.6) gr.; Length 37.4-40.9  (38.8) mm, width 20.1-24 (21.9) mm; (n=150)

Incubation: 80-90 (88.3) days (n=50 clutches). We incubate eggs in commercial incubators at 27-28 C (82-83F), though some nests that were over looked produced young that were later found in the outdoor pools with their parents.

Hatchlings: Wt. 8.4-11.2 (9.52) gr.; Standard carapace length 36.2.0-36.9 (36.5) mm.