Many species of mammals, either extinct in the wild or teetering close to it, have been successfully restored to parts of their range: the scimitar-horned oryx in northern Africa, black-footed ferrets in the United States, and Arabian oryx in Oman, to name but a few. These species would have been doomed without one thing: captive, or ex situ, populations in well-managed zoos.

A new study from Vietnam indicates the country’s diverse but increasingly imperiled host of mammals could benefit from such assurance collections alongside concerted efforts to strengthen protection of their habitats.

“The conservation goal today is not only to avoid extinction but also to focus on species recovery,” the study says.

The team of researchers from Germany, Japan and Vietnam found 20% of Vietnam’s 329 species of mammal are threatened with extinction at a global level, and more than one-third at a national level. The findings broadly reflect the bleak global outlook for mammals; the IUCN, the global wildlife conservation authority, estimates 27% of mammal species worldwide face extinction.

Localized mammal diversity

Vietnam is home to an impressive diversity of mammals, including the highest number of primate species in mainland Southeast Asia: 28 species in total, including endemic Tonkin snub-nosed monkeys (Rhinopithecus avunculus) and Delacour’s langurs (Trachypithecus delacouri). Camera-trapping surveys in the country’s network of national parks also frequently turn up an array of species, from rare ungulates and rabbits to ferret badgers and sleek but timid spotted linsangs (Prionodon pardicolor).

However, habitat loss, hunting for wild meat, and collection for the wildlife trade are pushing critical populations to the brink. The relentless loss of mammals from landscapes diminishes their crucial ecological roles, such as frugivorous seed dispersing, herbivorous vegetation control, or predator-prey dynamics. Indeed, studies show their loss from landscapes significantly reduces animal-dispersed plants’ ability to adapt to climate change.

Worryingly for the researchers, all primate species in Vietnam are threatened with extinction. They also identified knowledge gaps about several “micro-endemic” species that are confined to tiny localities and islands. “Species with such small distributions have a much higher risk of being extirpated and critically need immediate conservation actions,” the study says.

Adding to their concern is the finding that just two-thirds of threatened species of mammal currently receive protection under Vietnam’s wildlife laws, and only 17% are afforded any form of international trade regulation through CITES, the global convention on the wildlife trade.

While Vietnam’s existing protected area network covers much of the range of threatened mammals, the researchers found it affords little protection for species such as the Da Lat tube-nosed bat (Murina harpioloides), a globally endangered species whose entire global range remains unprotected.

The team spotlights the Hoang Lien Mountains in northeastern Vietnam, the Annamite Mountain Range along the border with Laos and Cambodia, and several offshore islands, such as Cat Ba in the northeast and Phu Quoc in the south, as particularly worthy of more conservation attention for mammals. These areas are home to critically endangered species, such as Cao-vit gibbons (Nomascus nasutus), southern white-cheeked gibbons (Nomascus siki) and red-shanked douc langurs (Pygathrix nemaeus).

‘One Plan’ for each species

Analysis of global zoo databases revealed that only 60% of Vietnam’s threatened mammal species are kept in zoo collections, mainly in facilities in the United States, Europe, Japan, Southeast Asia and India. Among the 45 threatened mammals absent from backup collections are iconic and critically endangered species like the saola ox (Pseudoryx nghetinhensis), the silver-backed chevrotain deer (Tragulus versicolor) and the large-antlered muntjac deer (Muntiacus vuquangensis).

The researchers advocate combining field-based and ex-situ conservation measures to recover mammal populations in Vietnam in line with the IUCN Conservation Planning Specialist Group’s “One Plan” approach. By leveraging expertise and resources from both inside and outside of species’ natural ranges, the “One Plan” vision is to have one integrated conservation plan per species.

Establishing assurance colonies under the care of specialized keepers in well-managed networks of zoos or local breeding centers is a critical part of this approach. In theory, these captive populations can buy conservationists time to address threats in the wild, such as reducing hunting pressure, curbing habitat loss, or controlling invasive species.

“If a species has gone extinct, this is irreversible,” study co-author Thomas Ziegler, coordinator of biodiversity and nature conservation projects for Vietnam and Laos at Cologne Zoological Garden in Germany, told Mongabay in an email. “If we still have threatened species in zoos, they are available for reintroductions, once the problem in nature is solved.”

In addition to specific locations and species for focus, the researchers recommend authorities strengthen the effectiveness of Vietnam’s network of protected areas by creating wildlife corridors for mammals, which often have vast home ranges or territories.

Proactive measures are vital

The study’s “big picture” overview of the status of mammals should prove helpful for planning purposes, according to Marcel Cardillo, a macroecologist at Australian National University, who wasn’t involved in the study. “Conservation planning is all about prioritization and making choices,” he said. “It is studies like this that inform decisions made at the national scale about where to allocate scarce conservation resources.”

Noam Werner, co-chair of the IUCN’s deer specialist group, said care must be taken in setting conservation priorities at a county-by-county level, as in the Vietnam study, since animals don’t adhere to national borders. “In a global perspective, resources should be prioritized for the protection of globally threatened species rather than species that might be nationally threatened but otherwise safe,” he said, noting that here might be merit in protecting charismatic species at a national level where indirect benefits spill over to less charismatic and globally threatened species that would have been otherwise overlooked.

Ultimately, captive-breeding programs are best viewed as one part of a balanced approach to species conservation, according to Cardillo. “It is only appropriate for species that are able to be successfully kept and bred in captivity,” he said. “It is [also] expensive, and we need to take into account factors like the capacity of zoos to keep and breed an ever-increasing number of threatened species, the ethics of removing individuals from dwindling wild populations, or the difficulty of reestablishing captive-bred animals into the wild.”

Maintaining healthy wild populations through preventive measures — such as involving local communities in conservation efforts, and strengthening the enforcement of wildlife laws and hunting bans — is also likely far more cost-effective in the long term than relying on rescue programs once species near extinction, Cardillo said.

“A more proactive outlook to conservation makes a good deal of sense everywhere, and especially for countries in which resources for conservation are limited,” he said. “Just as in medicine, prevention is better than cure in biodiversity conservation.”

Carolyn Cowan is a staff writer for Mongabay.

Citations:

Höffner, H., Nguyen, S. T., Dang, P. H., Motokawa, M., Oshida, T., Rödder, D., … Ziegler, T. (2024). Conservation priorities for threatened mammals of Vietnam: Implementation of the IUCN´s one plan approach. Nature Conservation, 56, 161-180. doi:10.3897/natureconservation.56.128129

Nguyen, T., Luu, A., Pham, H., Nguyen, H., Pham, T., Nguyen, M., … Nguyen, A. (2024). Systematic camera trapping survey for terrestrial vertebrates in Xuan Lien Nature Reserve, Vietnam. Biodiversity Data Journal, 12. doi:10.3897/bdj.12.e135746

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