On foot and by drone, radio tracking helps rehabilitate pangolins in Vietnam

  • Conservation NGO Save Vietnam’s Wildlife is employing radio tracking to follow rehabilitated pangolins rescued from the illegal wildlife trade, even in difficult terrain and when the animals burrow underground.
  • Tracking these pangolins on foot and using a novel radio telemetry drone has not only allowed the organization to assess the survival of released pangolins, but also improved the team’s knowledge of the secretive animals’ behaviors and habitat needs.
  • However, this radio-tracking work is vulnerable to funding challenges, as the expectation that conservation work result in published papers can make it difficult to find long-term funding for basic equipment like radio tags.

When the organization Save Vietnam’s Wildlife receives a pangolin rescued from the wildlife trade, it can take months to remind the scaly, housecat-sized mammal how to be a pangolin again. After treating any diseases or injuries, SVW caretakers place the pangolin in a small, semiwild enclosure. Here they monitor the rehabilitating animals to see if they’re behaving the way they would in the wild: if they’re investigating tubes of bamboo filled with ants, if they’re climbing trees, and if they’re digging burrows in the soft dirt. It can take up to a year for rescued animals to start acting like wild pangolins again — a delay compounded by ongoing criminal investigations, in which the animals are evidence.

But once a pangolin has been approved for release, SVW’s veterinarians might take an additional step: puncturing a hole in one of the pangolin’s fingernail-like scales and fastening on a small radio transmitter. Then they reintroduce the pangolin back to Vietnam’s forests and marshes, hoping that each animal has remembered enough to survive.

For the pangolin, radio tracking offers a tremendous boon to research. These mammals are shy and nocturnal. Because they live in dense forest and burrow underground, much of their habits are still unknown. For SVW, radio tracking pangolins on foot and using a new radio telemetry-equipped drone is revealing previously unknown facets of the animals’ lives, as well as refining the reintroduction process. But like many conservation organizations, their work is also limited by funding challenges.

A rehabilitated pangolin being released back into the wild.
A rehabilitated pangolin being released back into the wild. Image by Russell Gray.

By hand and by foot

Globally, all eight species of pangolin — four of which live in Africa and four in Asia — are gravely threatened by the illegal wildlife trade. Pangolin scales have been used in traditional Chinese and African medicine to treat a variety of conditions; their blood is considered a healing tonic, and their meat a delicacy across Asia.

Habitat change is also a significant factor, “especially in Asia, where development and urbanization is really expanding, pangolin populations are really affected by losing habitat,” says Charlene Yeong, a senior manager of conservation and wildlife health at the Singapore-based organization Mandai Wildlife and a member of the Pangolin Working Group at the IUCN, the global wildlife conservation authority.

As a result, three of the Asian pangolins are listed as critically endangered. Two of these species are native to Vietnam: the Sunda pangolin (Manis javanica) and the Chinese pangolin (Manis pentadactyla).

SVW started using radio tracking on pangolins in 2015, just a year after its founding. Though it now works with several different animals, the organization started with pangolins, tracking rehabilitated Sunda pangolins it received from law enforcement.

From the start, the team found that they could successfully track these pangolins using handheld radio receivers, which on average picked up a pangolin tag from as far as 200-300 meters (about 660-980 feet) so long as the animal was aboveground.

SVW began collecting data on how far these pangolins were moving and the impact of the environment on their behavior, and quickly found that they were breaking new ground. Outside of one small study from Singapore, there was no other research about the home ranges and movements of Sunda pangolins.

In 2023, SVW’s team published their first paper on the results of tracking pangolins, using data from 2018-2021 across three of Vietnam’s national parks. In addition to providing a baseline for the normal home range of Sunda pangolin, which average around 1.5 square kilometers (0.6 square miles), the research gave the team valuable information about where to release their scaly charges. For example, they discovered that male pangolins will usually high-tail it out of an area if they find signs of other male pangolins, such as scratch marks on trees, to avoid a conflict.

Two rehabilitated pangolins ready to be returned to the wild.
Two rehabilitated pangolins ready to be returned to the wild. Image by Russell Gray.

Unlike other tools such as camera traps, radio tracking allowed the SVW team to track pangolins directly to where they were sleeping during the day.

“This allows us to collect ecological info on what their movement is that day, and then collect what kind of micro-habitat information they are using most often,” says Russell Gray, a science adviser and technical specialist at SVW. “So, we can see that they’re using this specific tree and this area, and this amount of ants or leaf litter.”

That creates what Gray calls a “feedback loop” to rescue and release: “It’s essentially to increase the survival rate and make sure they are in the optimal location.”

This information is also helpful to animals awaiting release. Pangolins are difficult to keep in captivity, and yet they can end up stuck in SVW’s care due to pending criminal investigations. A better understanding of their diets and behavior gives pangolins the best chance of staying healthy in captivity until law enforcement gives them the all-clear.

Radio tracking also helped SVW decide which pangolins were worth the investment of tracking for the long term. The NGO found they were much more likely to successfully track females and individuals with a smaller body size, which move slower day to day and over shorter distances—while large males moved much faster, and tended to have bigger home ranges.

“If it’s a 12-kilogram [26-pound] male, it’s probably going to go missing in the first day, and you would be lucky to find it again,” Gray says.

From left to right, Russell Gray, Linh Le, and Tiffany Chen from Save Vietnam's Wildlife use hand-held radio telemetry to follow the tracking signal from a released pangolin on foot. Image by Russell Gray.
From left to right, Russell Gray, Linh Le, and Tiffany Chen from Save Vietnam’s Wildlife use hand-held radio telemetry to follow the tracking signal from a released pangolin on foot. Image by Russell Gray.

Following from above

Despite these successes, the SVW team kept running into a challenge during the dry season. In the rainy season, pangolins sleep in trees during the day, making them more easily detectable on foot. But during the dry season, when pangolins burrow underground during the day, the SVW trackers had to be within just 10 meters (33 ft) of a subterranean pangolin to detect it.

“When you’re looking for a pangolin in a tropical forest, you’re getting chewed up by bamboo, vines, thorns … it’s not always pleasant,” says Gray, adding that it can take an entire day to walk just 3 km (1.9 mi), and that’s when you know where you’re going. “So, it’s very, very difficult to find the animals when you’re on foot, you only have a 10-meter radius, and they can move up to a kilometer by the next day. Your chance of finding them is almost zero.”

Then, in 2019, a mutual connection linked SVW with Debbie Saunders, the founder of Australia-based Wildlife Drones. Saunders’ company creates drone-mounted systems that can pick up a radio tag signal from above, all this while flying as far as 5 km (3 mi) from the drone operator. Though Saunders was initially unsure if the drone would work in the tangled rainforest — the only research she could find on radio signals in such an environment came from defense journals, covering ground communications during the U.S. war in Vietnam — she agreed to fly to Vietnam at no cost for a trial of the system.

It was a success: despite the sometimes harrowing terrain, the system found 100% of the tags that the team had planted in the forest, even one hid beneath a fallen tree. Saunders returned to Australia and left the SVW team with a Wildlife Drones system, which they began using in the mountainous rainforests of Pù Mát National Park and U Minh Thượng National Park, a swampy wetland.

“[The drone] does exactly what we need,” Gray says.

Still, Gray emphasizes that the drone isn’t a perfect tool, and doesn’t entirely replace humans on foot. In Pù Mát, the drone could only track animals for a few days before SVW lost track of them, due to the mountains obstructing radio signals. The drone also can’t collect information about the habitat around the pangolin, as SVW staffers can. In many locations, the SVW team uses the drone to get a pangolin’s general location and then looks for it on foot, which reduces the overall search time and staff needs.

The drone can detect the radio tags’ frequency as well. This is important because the tags’ radio signal will increase in frequency, or beeps per minute, when the tag hasn’t moved in the past 24 hours, suggesting the pangolin in question has died.

This helps conservationists answer a vital question: are released pangolins surviving?

Lo Tien Bieu and Pham Thi Ha Nguyen flying a drone from the Wildlife Drones system.
Lo Tien Bieu and Pham Thi Ha Nguyen flying a drone from the Wildlife Drones system. Image by Russell Gray.

Funding challenges and future plans

Despite the fact that pangolins remain globally threatened, it’s a hopeful time to be working with these mammals. Just 10 years ago, pangolins were largely unknown outside of Asia. Today, pangolins are found in children’s books and brought to life by animators, and there’s growing public pressure to save these species. As a result, in 2020 pangolin scales were delisted from the Chinese pharmacopoeia, the approved list of ingredients in traditional Chinese medicine, and campaigns encouraging people not to use pangolin products are gaining momentum.

“Awareness has really increased, and that’s helped pangolin conservation in all its different aspects,” Yeong says. “Because more people now know what pangolins are and that consumption is a problem, more people are interested in helping in their conservation.”

Yet basic conservation for pangolins still faces challenges. At SVW, simply funding radio tags for their tracking work can be difficult: radio tags cost at least $300 each, while those with integrated GPS can be more than $1,000. The issue comes from the fact that many conservation donors want to support novel programs that lead to published material. While SVW’s work can lead to important ecological information, its pangolin tracking is primarily focused on ensuring that the animals survive.

“This makes repeated donors unlikely, or long-term tracking programs unlikely, because we cannot continue publishing the same information on the same species,” Gray says in an email to Mongabay.

Funding limitations have also affected their ability to use the Wildlife Drones system. Its software is expensive, at $3,000 per year, and any repairs can be pricey.

Yet the organization continues to press on in other directions. SVW is currently creating a center in Cúc Phương National Park to host its breeding program for Chinese pangolins, which are close to extinction in Vietnam.

Russell Gray watches a pangolin climb into a tree hole shortly after release.
Russell Gray watches a pangolin climb into a tree hole shortly after release. Image by Lam Le.

Similarly, at Mandai in Singapore, Yeong’s team saves sperm from any male pangolins it rescues in hopes of future assisted reproduction work. Indeed, many of the pangolins that Mandai receives are healthy, and have simply wandered into a home or yard. This gives the team an opportunity to study healthy individuals and develop normal baselines and techniques, which they then share with other groups. This culture of cooperation is one way this relatively small community continues to push pangolin conservation forward, even when resources are limited.

“We have been in contact with a number of rescue centers all throughout Southeast Asia, and we’re always learning from one another,” Yeong says. “Even the simplest things, like how do you house a really, really young pangolin — in a box, in a towel? Do you provide heat or not? Those sorts of things have been really helpful.

“There’s a lot more room to grow for sure,” she adds, “but it’s very encouraging to know that there are so many others out there fighting for pangolin conservation.”

Banner image: A pangolin fitted with a radio transmitter prior to re-release. Image by Tran Van Truong.

Rare baby Chinese pangolin born to rescued mom makes surprise debut at Vietnam sanctuary [VIDEO]


Gray, R. J., Le, D. V., Nguyen, H. T., Cau, L. N., Nguyen, T. V., Pham, T. V., … Nguyen, T. V. (2023). Home ranges and activity patterns of Sunda pangolins Manis javanica (Pholidota: Manidae) in Vietnam. Journal of Asia-Pacific Biodiversity, 16(3), 421-431. doi:10.1016/j.japb.2023.05.005