Field Surveys for Wild Rafetus
by¬†Dr. Gerald Kuchling¬†
The known world population of Yangtze giant softshell turtles (Rafetus swinhoei) presently counts four living specimens: two in separate lakes in the northern part of Vietnam (Red River drainage) and two in China where the only confirmed female from Changsha Zoo is on breeding loan at Suzhou Zoo since 2008, paired with the only surviving male in China. The male at the Suzhou Zoo appears to be very old and, despite many mating interactions over the last years, none of the numerous eggs the female laid annually produced any hatchlings and all eggs of 2011 were infertile.
Several surveys for Rafetus swinhoei took place over recent years in Vietnam, Laos and China. One of the two specimens in Vietnam, probably a middle-aged adult male, was discovered during such a survey in Dong Mo Lake in the Red River drainage in 2007. A survey along the Red River in Yunnan conducted by Conservation International in February 2007 confirmed the historic occurrence of the species in the Red River in Yunnan and listed several individuals which were recorded up to 1998, but could not find firm evidence for more recent captures or sightings.
The TSA funded a fact-finding mission to the Red River in Yunnan in September 2011 to confirm the information and data reported in 2007. Unfortunately, the team (led by Dr. Gerald Kuchling) also did not find evidence of recent sightings of the species. The main goal of their mission was to visit all Forestry Bureaus in Yunnan where Rafetus had been reported in the past to find out about past and current attempts to collect data on the species. They discovered that all Forestry Bureaus were aware of the rare and threatened status and the significance of the species and are monitoring the respective markets where softshell turtles are traded with the aim to rescue any Rafetus which might be offered for sale.
An interesting area of (at least former) Rafetus habitat seems to be a portion of the Red River. The team interviewed the now old fisherman who originally caught the last known specimen from this area in 1998 and tried to sell it. They found that fishermen still catch softshell turtles in this area, now mainly Pelodiscus, and sell them at the market in Langsha. Since 1998, the Forestry Bureau in Langsha has monitored the market every day to intercept and rescue any Rafetus which may turn up.
However, a main problem that the team discovered, and the likely reason why no Rafetus could be found since the 1990s appears to be that the only characteristic the forestry officers used and still use to identify Rafetus is that they are huge and gigantic. This means that any softshell turtle smaller than about 15-20 kg is considered to be a different, more common species and not worth any attention (Palea steindachneri, a medium-bodied species growing to over 20 kg, is for example also found in the area). Focusing exclusively on the discovery of huge and gigantic specimens completely ignores the fact that this may be the least common life stage turning up at markets particularly when populations are exploited or over-exploited. Even a huge turtle starts its life as a small hatchling and may take many years to grow to large size. Considering the large number of eggs a single female can lay annually (the Rafetus female in Suzhou laid about 200 eggs per year over the last four years) and that an individual female can do this over many decades if not a century (the female in Suzhou was already a large turtle in the 1930s), it is evident that the life history strategy of this species is to produce large numbers of eggs and hatchlings of which only very few will reach adulthood, similar to marine turtles. It is well known that in over-exploitation scenarios of large river turtles, large or huge adults are the first cohort to be extirpated. For several years after this event smaller size classes are still caught and consumed or traded. Extinction due to exploitation happens once all adult, reproducing individuals have been removed and, after a time lag of several years or a decade, all their still growing up offspring of previous reproductive seasons have also been removed. Since large Rafetus specimens were clearly still caught in the Red River in Yunnan in the late 1990s, it is highly unlikely that no small Rafetus specimens have been caught and sold at the markets over the last decade. Although since the 1990s the Forestry Bureaus along the Red River in Yunnan apparently allocated considerable time and resources to identify and rescue any Rafetus, they concentrated all their efforts exclusively on finding gigantic specimens, the least likely cohort to turn up. They ignored or overlooked any smaller ones which would have been much more common size classes in the local trade.
This discovery was the most important thing to come out of this survey trip.
Yunnan is fascinating since the drainages of all major south-east Asian rivers come closely together. There is a good likelihood that, accordingly, a number of different softshell turtles could still turn up in this area. However, the correct identification of different softshell turtle species in China still appears to be a problem even for experts. Over the last few years, authorities in China spent several times large sums of money to acquire large (and often moribund) specimens of Amyda cartilaginea and Nilssonia formosa in the believe that they were rescuing Rafetus swinhoei. This apparently widespread inability to correctly indentify softshell turtle species hampers past and present efforts to find and rescue surviving specimens of Rafetus swinhoei in China.
With significant habitat destruction caused by hydro-electric dams affecting the previous range of Rafetus, time may be running out fast to identify and rescue any surviving specimens. Since finding Rafetus specimens may not be possible during a time-limited survey with a small team of biologists, a major aim of efforts moving forward will be to build up the capacity of Forestry Bureaus in Yunnan to identify and rescue Rafetus¬∏ regardless of their size. With that goal in mind, the single major necessity is to compile a clear identification kit for all size classes of the different softshell turtle species which may be found or which may turn up in Yunnan and to distribute these kits to all forestry offices in the area. Doing so will significantly build up the capacity of Forestry Bureaus in Yunnan to identify and rescue Rafetus swinhoei specimens of any size which may still turn up in the local food trade and to make them available for captive breeding.