Search for the silver-backed chevrotain

The silver-backed chevrotain (Tragulus versicolor) is a small ungulate known only from Vietnam. The species has been lost to science for almost 30 years. We set out to find it.

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By Andrew Tilker and An Nguyen

The chevrotains are unique among the ungulate family: picture a deer-like animal the size of a toy poodle, with short thin legs stuck into a stocky body, and two miniature fangs that protrude vampire-style. What ecologist wouldn’t want to study such an intriguing animal? But there was a deeper motivation to our interest in the species: the silver-backed chevrotain (Tragulus versicolor) was, by all accounts, a species that was lost to science. 

The silver-backed chevrotain was described in 1910 from four specimens that were collected near the city of Nha Trang in southern Vietnam. The scientist who described it must have immediately known that he had something unique: the species’ slate-gray coloration and distinct throat markings clearly set it apart from the more common lesser chevrotain (Tragulus kanchil). For the next 80 years, there were no additional scientific records of the species. All that changed in 1990, when a fifth animal turned up in south-central Vietnam. And then the silver-backed chevrotain again slipped off the scientific radar. Given the drastic increase in snaring that has occurred across Vietnam in the past three decades, scientists were unsure whether the species still existed.

We set out to find the silver-backed chevrotain. One of the first challenges we faced was simply deciding where to look. The fact that the species has only been recorded from two places didn’t make things easy. Furthermore, because the last reliable record was decades old, we didn’t have a fresh trail to follow. A group of us met up one hot day in central Vietnam and, over copious amounts of green tea and café sua da (iced coffee), thought about these questions. In the end, we decided to target our search on the dry coastal forests in the southern part of the country. This was the general area of the type specimens. Also, a fair amount of camera-trapping has occurred in the wet evergreen forest habitat that predominates across much of Vietnam, but little work has been done in the drier coastal areas. So we headed for the arid, thorn-choked scrub forests in the south.

Coastal forests of southern Vietnam. Photo: An Nguyen.

But that still left a large area to cover. To narrow down the search area, we conducted rapid interviews across three Vietnamese provinces. During the interviews, we asked villagers and protected area staff to describe the wildlife in the region. We asked about all mammal species, but of course were most interested in information on chevrotains. We were intrigued when locals reported the existence of gray-colored chevrotain in two different forest areas. Could these animals be the lost silver-backed chevrotain? We were hopeful, but didn’t want to jump to any conclusions. We made a plan for further surveys in these locations. At the end of the interviews, we opportunistically set three camera-traps in one of the areas where locals reported gray chevrotain. We had the cameras from another project – so why not use them?

Setting camera traps for silver-backed chevrotain. Photo: An Nguyen.

We returned three months later armed with 30 new camera-trap units with the plan of conducting an intensive search effort in what we deemed was the most promising area. After a week of hot, dusty, machete-wielding fieldwork we had all the units out. The last thing to do before heading home was to check the three cameras that we had set earlier. We retrieved the units and flipped through the photos and found – to our complete surprise – that all cameras had images of a gray-colored chevrotain. The animals had all the morphological characteristics of the silver-backed chevrotain: distinct bi-coloration, with an ocherous head and neck and shoulder, and slate-gray hindquarters, complete with non-convergent throat markings. After confirming the identification with a few mammal experts we could come to only one conclusion: We had found the silver-backed chevrotain!

Silver-backed chevrotain camera-trap images. Photo: SIE/GWC/Leibniz-IZW/NCNP

Over the course of the next few months we obtained more than one thousand additional silver-backed chevrotain photographs in that same area. With every photo, we had one more glimpse into the life of this secretive species, and we slowly started to piece together some basic facts about its ecology. The species was diurnal and mostly solitary, though we did record a few animals in pairs. It appeared to be relatively common in the area that we had camera-trapped. However, this does not, in itself, mean that the species is common across the wider forest area. Indeed, we knew from our interviews that locals believed that chevrotain populations had plummeted in the region over the past five to ten years. 

The silver-backed chevrotain has resurfaced to scientific community for only the third time. But it would be a mistake to think that history can’t repeat itself. And so we are left wondering: What will it take to ensure that the silver-backed chevrotain does not become lost once again? Given the snaring crisis in Vietnam, is it possible that this recently-found species could slip into extinction? We urgently need more information. From a research perspective, the two highest priorities are to assess the population status in the site where it was recorded for this study, and to search for additional populations. Only when we make progress on these overarching questions will we be able to develop an evidence-based conservation plan for the silver-backed chevrotain.

All of this will be an immense undertaking. It won’t be quick, easy, or cheap. And yet – we consider ourselves fortunate to have the opportunity to continue working on this remarkable animal. Protecting the silver-backed chevrotain is about more than protecting a single small deer-like animal that lives deep in the forests of Southeast Asia. It is about protecting an animal that is only found in Vietnam, and is therefore a unique part of its biodiversity heritage. It is about protecting a species that has been largely overlooked in the past, and needs a voice. And it is about protecting a species that has been lost to science and, now that we know it is still out there, has given conservationists a rare second-chance to ensure its survival.

For more information on the silver-backed chevrotain check out our paper here. For more information on the Search for Lost Species see here.

Andrew Tilker

Asian Species Officer, Global Wildlife Conservation