Hanoi's Giant Softshell Faces an Invasive North American Turtle


Rafetus swinhoei Photo Credit:
Asian Turtle Conservation Network
Turtles have cultural importance in the societies of Southeast Asia. In Vietnamese culture the Ho Guom Turtle (Rafetus swinhoei) is considered holy because of a 15th-century legend describing how King Le Loi drove out invading Chinese with a magical sword, which the gods gave him and which he later returned by giving it to the lake's turtle, which swam it back to the gods. Hoan Kiem Lake is an oasis in urban Hanoi that attracts tourists and locals alike, and the place to go to catch a glimpse of the 300-kilogram Ho Guom Turtle, it’s most famous resident (there is a population of these turtles in the lake, not just one individual). Today (December 21, 2010), m&cnews.com is reporting that Vietnamese scientists are urging Hanoi authorities to wipe out the invasive Red-eared Slider (Trachemys scripta) which is believed to be a threat to Hoan Kiem Lake's legendary chelonian. Professor Ha Dinh Duc, an expert on the giant softshell Rafetus swinhoei, said 'Hanoi's authorities need to make a plan to kill these invaders because if there are no timely and proper measures, red-eared turtles would eat all foods of our native turtle...They even eat all plants in the lake, and the lake would not be green anymore."

Many Hanoians release the North American Red-eared Slider into Hoan Kiem for good luck at holidays, such as the Tet New Year. Thus, they have created the situation, said Pham Dinh Quyen, general secretary of the Vietnam Association for Conservation of Nature and Environment. Red-eared Sliders are now doing well in the lake.

Rafetus swinhoei is probably the world’s largest and rarest softshell turtle species (Family Trionychidae). There are few recent records of them, and what we known about them suggest they have a discontinuous and relictual distribution. The species is known from Tai Hu Lake and the Suzhou area, west of Shanghai, the Red River drainage in Yunnan, in southern China, and from the same river system in northern Vietnam. Rafetus swinhoei have also been reported from Thanh Hoa Province, Vietnam and this is the most southern reported locality for the species, if its presence can be documented. Rafetus swinhoei was already rare in the 1870’s, when Pierre-Marie Heude collected some specimens from the Tai Hu Lake area. In 2009 there were only four captive specimens in China and one in Vietnam, although fishermen’s accounts indicate that some wild animals existed as recently as 10-20 years ago (Le and Pritchard, 2009). Search for museum specimens was conducted by Peter Pritchard, who located about 20 specimens, most of them decades old, and nearly all had been misidentified as species of Pelochelys. Taxonomic confusion started when Heude (1880) ignored John Gray’s description of Oscaria swinhoei (Gray, 1873) and named five species within the genus Yuen to a group of swinhoei specimens from the eastern population. This was not sorted out until 1998 when Meylan and Webb (1998) carefully examined Gray’s type specimen in the British Museum of Natural History and confirmed the validity Rafetus swinhoei. To add to the confusion, Ha Dinh Duc (2000) described Rafetus leloii, based on specimens collected from Hoan Kiem Lake in downtown Hanoi, but Farkas and Webb (2003) placed leloii into the synonymy of swinhoei.

Rafetus swinhoei appears to be on the brink of extinction. Unless immediate action is taken to increase its populations it seems probable that it won't last the century.

Literature

Asian Turtle Conservation Network.

Farkas, B. L. and R. G. Webb, 2003. Rafetus leloii Ha Dinh Duc, 2000 – an invalid species of softshell turtle from Hoan Kiem Lake, Hanoi, Vietnam (Reptilia, Testudines, Trionychidae). Zoologische Abhandlungen 53: 107-112.

Gray, J. E. 1873. Notes on Chinese mud-tortoises (Trionychidae), with the description of a new species sent to the British Museum by Mr. Swinhoe, and observations on the male organ of this family. Ann. Mag. Nat. Hist. 12:156-161.

Ha, D. D. 2000. A new species of the genus Rafetus (Family: Trionychidae) from Hoan Kiem Lake of Vietnam. Archeology Magazine 4:104.

Le, M. D. and P. Pritchard. 2009. Genetic variability of the critically endangered softshell turtle Rafetus swinhoei: A preliminary report. In the Proceedings of the First Vietnamese National Symposium on Reptiles and Amphibians, pp. 84-92.

M&CNews.com December 21, 2010.

Meylan, P. A . and R. G. Webb, 1988. Rafetus swinhoei (Gray) 1873, a valid species of living soft-shelled turtle (family Trionychidae) from China. Journal of Herpetology 22:118-119.