In the early 1990s, biologists in southeast Asia discovered a species of turtle unknown to science. But there was a catch: They didn't know where it came from. Cuora picturata, as the new turtle was formally named, was found only in markets where it was sold for food.

Nearly two decades later, a clever piece of biological sleuthing has found the native home of C. picturata. The discovery offers hope not just to C. picturata, but to other turtle species known only from markets.

"It's frustrating. You see this animal being exploited, and likely facing extinction," said Bryan Stuart, a biologist at the North Carolina Museum of Natural Sciences, whose search for C. picturata's home was described April 1 in Biological Sciences. "But there's little that conservation can do, because we're missing the basic information necessary for conservation: Where does this species occur in the wild?"

Stuart and other researchers weren't starting from scratch, however. From the location of markets where C. picturata was sold, they figured the turtles were captured in southern Vietnam or across the border in Cambodia. The turtle also resembled two other known box turtle species, Cuora galbinifrons and Cuora bourretti. Genetic comparisons proved their relation.

Those other turtles live in wet forests with closed canopies. The place best fitting that description in southern Vietnam was the Langbian plateau, at the southern tip of the Truong Son mountains – and C. bourreti lived in the central part of the mountains, with C. galbinifrons to the north.

The puzzle pieces were coming together, and there was one more clue. Where C. galbinifrons lived, so did Hylobates leucogenys, a species of gibbon, and Pygathrix nemaeus, a species of douc langur. Likewise, where * C. bourretti* lived, so did a Hylobates species closely related to the northern gibbons, and a Pygathrix species closely related to the northern doucs. Such so-called "co-occurences" result from historic events – a new river, a climate change – that split ancestral populations into separate groups. The Langbian plateau also had its own unique gibbon and douc langur; if the pattern held, C. picturata should be its box turtle.

But though Stuart could guess where C. picturata might be, he still needed help finding it. Enter Tri Ly, a biologist at the University of Science in Ho Chi Minh City, who had just finished his undergraduate studies and approached Stuart in search of a project.

Ly traveled to the Langbian plateau, where he interviewed villagers and met with hunters. In July of 2010, the first expedition set off. Hunting dogs were used to find turtles in the dense jungle foliage, but their barks were often false alarms: the group found king cobras, mouse deer, squirrels, monkeys – but no turtles.

Finally, on July 5, 2010, hiding from the dogs under a pile of dry leaves at the base of a rattan bush on the slope of a hill, was a single female C. picturata, seen for the first time in the wild. "I was totally amazed and elated," said Tri Ly.

Three separate expeditions recovered a total of eight turtles, firmly establishing the Langbian plateau as their home. Unfortunately, the turtles' habitat is being lost to agriculture and coffee plantations, but the findings are an essential first step toward conservation.

>'It is hoped that ... efforts such as ours will soon identify the mysterious origins of these other rare species that are known to scientists only by turtles bearing price tags.'

Beyond knowing what places need protection, conservationists now know where turtles bred in captivity can be released. Without this knowledge, C. picturata could end up in the conservation equivalent of life support, bred in captivity in perpetuity.

Stuart and Ly hope their efforts will inspire other biologists in southeast Asia, which is currently experiencing what's known as the "Asian turtle crisis": Millions of turtles are sent each year to China, threatening many species with extinction. At least three other box turtle species – C. zhoui, C. mccordi and C. yunnanensis – are known only from markets.

"It is hoped that focused field efforts such as ours will soon identify the mysterious origins of these other rare species that are known to scientists only by turtles bearing price tags," wrote Stuart and Ly.

Images: 1) Female Vietnamese box turtle (Biological Conservation). 2) A map of southeast Asia and the box turtles' ranges (Biological Conservation).

See Also:

Citation: "Market Turtle Mystery Solved in Vietnam." By Tri Ly, Huy Duc Hoang and Bryan L. Stuart. Biological Conservation, online publication, April 1, 2011.