It’s not looking good for the saola.
If it still exists, it is one of the world’s rarest large mammals — a deerlike creature from the mountainous rainforests of Vietnam and Laos that’s been called “Asia’s unicorn” because of its scarcity. But the last living saola (Pseudoryx nghetinhensis) was seen in 2013, in photographs from a motion-triggered trail camera. Even hopeful experts think there are now fewer than 100 still alive. “That number is extremely optimistic,” says University of Copenhagen wildlife geneticist Rasmus Heller. “The real number is probably much lower … and it’s possible that there are actually zero.”
A new genetic study of saolas could help the animals survive. Saolas became known to science in 1992, through trophies in the homes of subsistence hunters in Southeast Asia’s rugged Annamite mountains (called the Truong Son in Vietnam and the Sai Phou Louang in Laos.) The research used DNA from 26 individual saola hunting trophies to establish a “reference genome” for the species — the first complete saola genome ever derived, Heller and colleagues report May 5 in Cell.
As well as revealing new details of the animals’ ancestry, the reference genome could better help locate saolas through environmental DNA, genetic material in cells shed into waterways and other parts of their habitats.
And it shows there are two populations of saolas that diverged between about 20,000 and 5,000 years ago — possibly when their habitats were splintered by changes in climate. The researchers estimate that 12 saolas will be needed for a captive breeding program, and the study sets out how mixing these two genetic populations could help them avoid extinction. “What we’ve done is to quantify the benefits of mixing them together,” Heller says.
Saola samples
Researchers examined DNA from 26 saola hunting trophies in Vietnam and Laos and found the animals had come from two distinct populations (blue and orange dots). The purple shading indicates the saolas’ expected range.
Several of the study authors are based in Vietnam, including biologist Minh Le at Vietnam National University in Hanoi. Le helped collect the saola samples, and stresses that traditional hunting with snares along animal trails now threatens several species. “Not just saola, but also predators like tiger and leopard have been virtually extirpated in much of the Annamites,” he says. “Other species will follow soon if immediate conservation measures are not implemented.”
Le also notes that while recent surveys for saolas in Vietnam have been negative, more encouraging signs could come from Laos, where the U.S.-based Saola Foundation is working to locate and conserve the animals.
The foundation’s chief executive, Lorraine Scotson, says conservationists in both countries support the search for saolas, but her group has determined the best chance of establishing a breeding program right now is in Laos. “Our hope is to broaden our search to other parts of the saola’s range as soon as resources permit,” she says.
Rob Timmins, the foundation’s technical director in Laos, says the group is dedicated to ensuring the survival of saolas through a breeding program, even if there prove to be only a few founder animals left.
“Mauritius kestrels have recovered from the brink of extinction on the basis of just four founders.… Galapagos giant tortoises have recovered from 15 founders…. California condor from 23 individuals,” he says.
Timmins is one of the few who has seen a living saola — a female dubbed “Martha” who survived captivity for a few weeks in Laos in 1996. Timmins has since scoured both Vietnam and Laos for traces of them and may have spent more time in saola habitats than anyone else.
The American biologist Bill Robichaud, a champion of saola conservation who has often collaborated with Timmins, also saw Martha in 1996 — to date, the only living saola ever seen by Western scientists. “I realize now what a great gift and privilege that was,” he says. “Who knew back then she would be the only one?”