Second breeding attempt for Rafetus swinhoei in China leads to cautious optimism

The epic move of the last Chinese female Yangtze giant softshell turtle (Rafetus swinhoei) from Changsha Zoo to the last Chinese male at the Suzhou Zoo in 2008 resulted in successful mating, producing two clutches totalling over one hundred eggs. Despite this success, unfortunately none of the eggs hatched. About half the eggs of the second clutch were not properly shelled and many cracked during laying. Nutritional deficencies of the long-term captive female ‚Äì over 70 years in captivity - were most likely to blame for this setback, and apparently caused any fertilized eggs to die early during development.   Despite this disappointment, this event captured the attention of the global conservation community, and the remarkable story was featured in a PBS/Nature special called The Loneliest Animals that aired on April 19, 2009. Click here to view. 

This problem with the eggs had been foreseen and a nutritional workshop held in Changsha in May 2007 had resulted in some improvements to the diet of the female. Since yolk formation for eggs in turtles takes many months, there is always a delay until dietary improvements can result in better egg hatchability.  So, in actuality, a balanced diet is needed in the year prior to oviposition to improve hatching success. Unfortunately however, due to concerns of the Chinese stakeholders that the female did not eat enough after her move to Suzhou, her diet was reverted back to primarily meat and liver in May 2008. Only since August 2008 was this problem addressed by providing an improved diet to the female including vitamin and calcium supplements.  Concerns for the well-being of the female by her Chinese guardians resulted in recommendations for dietary changes being slowly implemented.   But now chicken parts with bone, fresh whole fish, crayfish and gutted quail with calcium supplements are offered routinely; this bodes well for the future but somewhat clouds our optimism for 2009.  Despite this, we have installed a rearing tank with filtration for juveniles in anticipation of success.
Since June 2008, the male and female were kept separate in the divided breeding pond at Suzhou Zoo. The gate was again opened in the morning of 26 April 2009 and a likely copulation took place the same day between 13:05 and 14:45. On 28 April from 13:08 to 13:41 another possible copulation was observed. Numerous other interactions of the male and the female took place, but with the male often mounted for only short periods of time (< 5 min). On 07 May the female twice vehemently swam away from the male when he tried to mount her and they were separated and the gate closed. The gate was opened again in the morning of 10 May, and again the female fled twice when the male tried to mount her. For this reason the gate was closed again at noon.

The weather was unusually hot in Suzhou in early May 2009 and the behavior of the female suggested that she ovulated earlier than in 2008 when she first nested on 6 June. For this reason Gerald Kuchling returned to Suzhou on 31 May 2009 and the female nested the same night, depositing 56 eggs in a nest on her sand beach. TSA again hired Chinese-American biologist Emily King to help with monitoring breeding and egg incubation and on 04 June the nest was dug out. Four of the eggs were found slightly cracked and 28 eggs were placed into incubators in either sand, vermiculite or hatchrite at 29, 31 and 33¬∞C. Incubation procedures have been modified this year to ensure adequate humidity and hydration and multiple incubation medias are being tried. The other half of the clutch was left in the nest with two temperature data loggers. However, no clear banding of eggs could yet be seen on 09 June. From 5 to 13 June the male and female were again paired up for breeding, and then separated on 14 June due to the female‚Äôs  non-receptivity.

A disturbing trend in 2009 is that the now-tamer female Rafetus accepts junk food (bread, crackers, chips etc) thrown into her pond by zoo visitors, eating so much that she is not particularly hungry at feeding time.  She was also seen eating plastic bags and candy wrappers, which threatens the health and survival of the female and potentially jeopardizes the entire breeding program.  An improved method of separation ‚Äì glass panels ‚Äì limiting zoo visitor‚Äôs access to the breeding pond is imperative. However the costs of are currently prohibitive, estimated at $30,000 U.S.  For all these reasons it is not yet clear if this second breeding attempt will have better success than the first. It is obvious that further improvements to husbandry and the enclosure are needed. The good news is that Changsha Zoo is now committed to leaving their female at Suzhou Zoo until the sucessful production of hatchlings.  

This effort would not have been possible without the coordination and logistic support of the WCS China office.  The 2009 breeding attempt was again funded by the Turtle Survival Alliance, with generous financial support from Kadoorie Farm and Botanic Garden, WWF Canada, Alessandro Fornetti, David Shapiro, Frank and Kate Slavens, Taste of Thai, Jacksonville Zoo, and Thomas Jacoby.  Special thanks to all those that purchased Rafetus prints this past year, the proceeds of which went to help support this remarkable effort.  

Gerald Kuchling 

Lu Shunqing
WCS-China Program