Yangtze giant softshell turtle

R. swinhoei eats fish, crabs, snails, water hyacinth, frogs, and "green rice leaves".

The Yangtze giant softshell turtle may lay from 20 to more than 80 eggs. It nests at night and during the morning.[11]

A fertile female from the Changsha Zoo was introduced to the only known male in China, a 100-year-old individual in the Suzhou Zoo, in 2008. The female, who is over 80 years old, was said to settle in well after her 1000-kilometre (600-mile) move, and biologists were optimistic for breeding success. The move was coordinated by the Wildlife Conservation Society and the Turtle Survival Alliance.[24] In July 2013 National Geographic reported that in the sixth breeding season for the Suzhou mating pair, 80 eggs have been laid, but none were fertile.[25]

Despite its massive size and distinctive appearance, this species is extremely secretive and only rarely comes up to breathe, largely preferring to stay submerged deep underwater. This may be part of the reason why it is so difficult to positively identify and confirm wild sightings of this species.[26]

Illustration by G.H. Ford, from Gray's original description, 1873

The species became known to Western science in 1873, when John Edward Gray, the turtle expert at the British Museum, described the specimen sent to him from Shanghai by English biologist Robert Swinhoe.[27] He named the species Oscaria swinhoei, and described it as "the most beautiful species of Trionychidae that has yet occurred."[28]

In 1880, the Shanghai-based French Jesuit Pierre Marie Heude obtained several specimens of this turtle, from the Huangpu River (near Shanghai) and Lake Tai (near Suzhou). He thought them sufficiently different from each other to describe them as five distinct species: Yuen leprosus, Yuen maculatus, Yuen elegans, Yuen viridis, and Yuen pallens.[29] The genus name, Yuen, presumably comes from the Chinese 鼋 (transcribed yüen in the Wade-Giles system, or yuan in the modern Hanyu Pinyin), which means a large turtle.

Later zoologists classified these turtles as belonging to the genera Trionyx, Pelodiscus, and Pelochelys; in 1987, Meylan categorized this species under the genus Rafetus.[29]

The placement of the related or conspecific Hoan Kiem turtle, Rafetus leloii, remains poorly known and controversial. Most herpetologists accept R. leloii is a junior synonym of the Yangtze giant softshell turtle,[10] though some Vietnamese biologists, such as Ha Dinh Duc, who first described R. leloii, and Le Tran Binh, assert R. leloii to be distinct. Le points out genetic differences, as well as differences in morphology.[30] However, Farkas et al. repeated their 2003 conclusion in 2011, attributing differences between specimens to age, and pointed out that the genetic sequences used were never sent to GenBank. They also criticized the fact that Le et al. violated ICZN Code by renaming the species from R. leloii to R. vietnamensis on the grounds of "appropriateness".[9]

The Yangtze giant softshell turtle is on the brink of extinction due to habitat loss, legal overtrade, lack of legislation to control these wildlife trading, trafficking, the human food preferences,[31] hunting for subsistence and local consumption, and the use of the carapace and bones in alternative medicine. Skulls are often kept as trophies.[11] A recent plan to build hydropower cascade of 12 dams on the Red River in China may flood all of its habitat and change the ecosystem of lower Vietnam.[32]

Conservation efforts are concentrated on breeding captive turtles in China and searching for live specimens in the wild. An agreement was made to transfer the only known remaining female specimen located at the Changsha Zoo to the Suzhou Zoo to breed with the male specimen there. Also, efforts are being made to improve conditions for breeding at both the Suzhou Zoo and Western Temple in Suzhou. A workshop on the Rafetus Conservation at Yunnan was held by CI-Shanshui. Local Chinese scientists are searching for the last existent individuals.[33] The two specimens were able to produce two clutches of eggs, with over half of them being fertile, though all of them perished before hatching.[34] The Turtle Survival Alliance released a statement saying, "A number of the eggs had very thin shells, suggesting that the diet of the animals prior to breeding was not optimal."[35] The two turtles were prepared for another round of mating, while being fed a high-calcium diet in an effort to strengthen the eggs. Liu Jinde, the director of the zoo said, "We've worked very hard on this, We ought to succeed. The turtles are very healthy."

The scientists began preparing to mate the two once again in May 2009, which fell within this species' breeding season,[36] but in the fall of 2009, the zoo announced that despite laying 188 eggs, the eggs were infertile and would not hatch.[37] The Turtle Survival Alliance issued a statement explaining the infertility was due in part to the turtle's poor diet and the group expressed concern that the zoo's patrons had thrown trash into the turtle's enclosure that, if eaten, could endanger the health of the turtles.[37] On June 15, 2010, the female laid a total of 63 eggs. Half of the eggs were left in the sand to incubate naturally, while the other half were moved to incubate at varying temperatures and humidities. Once again, they were infertile.

In 2015 artificial insemination was attempted, a first for this species.[38] In May 2015, the female was successfully inseminated. Semen was extracted from the sedated male using electro-ejaculation. By late July, the female had laid 2 clutches of eggs, totaling 89 eggs, but none were viable.[39] The female later died in April 2019 following another artificial insemination attempt.[13][14][15]

As of mid-2017, conservationists are searching for any possible wild individuals in the remote parts of China. A major target of the survey are parts of the Red River in Yunnan Province. Locals in the area have reported seeing 1-2 turtles that have a similar description to that of this species, meaning that there is a small possibility the species may still survive in the wild.[40] In Oct. 2018, the Asian Turtle Program announced that it was interviewing local people to collect data to guideline searches for R. swinhoei in the very large area of flooded valleys formed by damming the Da River.[41]

In April 2018, conservationists confirmed the existence of a second wild individual in Xuan Khanh Lake, Vietnam. The individual was photographed two times in 2012 and 2017, but both times the photograph was blurry and provided little confirmation of its identity. Using traces of the turtle's DNA in the lake's water, the specimen's identity was confirmed as R. swinhoei.[42] In Nov. 2018, it was announced that a second, smaller individual of R. swinhoei also lives in Dong Mo Lake; this individual had long been confused with the larger turtle until the summer of 2018, when both turtles were seen raising their heads out of the water at the same time.[43] In 2020, a survey at Dong Mo managed to capture one of the turtles and obtain genetic samples, and found that it was a female, representing the first known female R. swinhoei since the death of the captive female in 2019.[16] This female died from unknown causes in early 2023.[18]

There are also several other modern accounts of surviving individuals of R. swinhoei, although most of these are unverified or have not been followed up on. Following the creation of the Madushan Dam in China's Yunnan Province, local fishermen regularly reported sightings of one to two very large softshell turtles in the reservoir. However, extensive surveys in 2016 and 2017 were unsuccessful in finding any such turtles.[44] At some point prior to 2015, a survey team from the conservation group Turtle Island apparently managed to locate an individual of R. swinhoei in a section of the Red River between two reservoirs. However, the individual was never trapped and was at high risk of being caught by fishermen.[45] Another search by the same group found a pond in Laos where a R. swinhoei had apparently lived for over 45 years before a monsoon in 2013, during which the individual moved to a nearby river and was never seen again.[45]