Given that there are only four of the world’s rarest freshwater turtle, Swinhoe’s soft-shell turtle’s (Rafetus swinhoei), known to exist in the wild or captivity today, the news this fall from the Suzhou Zoo’s captive breeding program that their male may be infertile has forced researchers to reconsider the program’s future.
Not only is it the rarest freshwater turtle species, Swinhoe’s softshell turtle is also famous for it role in Vietnamese legend as the fabled Sword Lake Turtle, which inhabits Hoàn Kiếm Lake (“The Lake of the Returned Sword”) in Hanoi, Vietnam. But of the handful of Swinhoe’s softshell turtles known to scientists to exist in the wild or captivity in recent years, five have died since the 1990s, leaving only four remaining: one in Hoàn Kiếm Lake, one in the wild in Đồng Mỏ Lake west of Hanoi, and two in captivity, the latter now both part of the Suzhou Zoo’s captive breeding program.
Since 2008, when the Changsha Zoo’s female, “China Girl,” was relocated to Suzhou, scientists at Suzhou Zoo have undertaken a captive breeding program with their older male turtle. But despite repeated bouts of courtship displays and mating between the pair in the years since, the resulting eggs – this year’s, too – have failed to hatch. Remediative actions to date, including steps to improve their diet by constructing a glass wall to prevent visitors from tossing junk food into their inclosure, provisioning the pair with a more natural diet (e.g. whole shrimp, freshwater crayfish, fishes, freshwater snails, frogs, quail, pigeons), and redesigning their enclosure to allow the pair more time together, have proven unsuccessful.
This fall with the support of the Turtle Survival Alliance, Kaitlin Croyle, a research assistant with the San Diego Zoo’s Institute for Conservation Research, visited the Suzhou Zoo to remove the yolk membranes of fresh laid eggs and examine them microscopically for sperm, a technique known as ovo sperm detection. Croyle was unable to detect sperm, confirming what many have long suspected, that the male is likely infertile.
Despite this setback, with the permission of Chinese officials Rafetus stakeholders are instead exploring the option of artificial insemination. But to do so, they need a new male Swinhoe’s softshell turtle. To this end, herpetologist Gerald Kuchling is following up on anecdotal observations of possible Swinhoe’s in the Red River in Yunnan Province, China. There, Dr. Kuchling and Dr. Rao Dingqi at the Kunming Institute of Zoology are using collapsible “cathedral traps” designed to trap deep waters, but which are also buoyant enough to allow turtles to surface and breath. Unfortunately, scientists aren’t the only ones interested in catching Swinhoe’s soft-shell turtles. Locals and fisherman see the turtles as food. According to an August 2014 update by Kuchling in the Turtle Survival Alliance’s magazine, Turtle Survival, “There is a real danger that the last wild R. swinhoei in China could end up at a banquet rather than in a breeding program.”