Thai tiger numbers swell as prey populations stabilize in western forests

The tiger population density in a series of protected areas in western Thailand has more than doubled over the past two decades, according to new survey data.

Thailand is the final stronghold of the Indochinese tiger (Panthera tigris corbetti), the subspecies having been extirpated from neighboring Cambodia, Laos and Vietnam over the past decade due to poaching, habitat loss and indiscriminate snaring.

Persistent markets for tiger skins, bones and other body parts used in traditional medicines in China and Vietnam drive poaching and illegal trade, which present the main threat to the big cats.

Fewer than 200 tigers are thought to remain in Thailand’s national parks and wildlife sanctuaries, only a handful of which are sufficiently undisturbed and well-protected to preserve breeding tigers. 

The most important of these protected areas for tigers is the Huai Kha Khaeng Thung Yai (HKK-TY) UNESCO World Heritage Site, which comprises three distinct reserves out of the 17 that make up Thailand’s Western Forest Complex (WEFCOM). Together, these three reserves — Huai Kha Khaeng Wildlife Sanctuary, Thungyai Naresuan West and Thungyai Naresuan East — account for more than a third of the entire WEFCOM landscape.

Now, a new study published in Global Ecology and Conservation documents a steady recovery of tigers within the HKK-TY reserves since camera trap surveys began in 2007. The most recent year of surveys, which concluded in November 2023, photographed 94 individual tigers, up from 75 individuals in the previous year, and from fewer than 40 in 2007.

Healthy tiger families  

The study findings reveal that the tiger population grew on average 4% per year in Hua Kha Khaeng Wildlife Sanctuary, the largest and longest-protected of the reserves, corresponding to an increase in tiger density from 1.3 tigers per 100 square kilometers, to 2.9 tigers/100 km2. 

“Tiger recoveries in Southeast Asia are few, and examples such as these highlight that recoveries can be supported outside of South Asia, where most of the good news [about tigers] appears to come from,” said Abishek Harihar, tiger program director for Panthera, the global wildcat conservation organization, who was not involved in the study.

Among the camera trap footage gathered in HKK-TY over the years were encouraging scenes of healthy tiger families, including one instance of a mother tiger and her three grownup cubs lapping water and lounging in a jacuzzi-sized watering hole. The tiger family stayed by the water source for five days during the height of the dry season.

The team of researchers from Thailand’s Department of National Parks, Wildlife and Plant Conservation, the Wildlife Conservation Society, Kasetsart University, and India’s Center for Wildlife Studies deployed camera traps at more than 270 separate locations throughout the HKK-TY reserves, amassing 98,305 days’ worth of camera-trap data over the 19-year study period.

Using software that identifies individual tigers by their unique stripe patterns, they built a reference database of all known tigers frequenting the three reserves. A total of 291 individual tigers older than 1 year were recorded, as well as 67 cubs younger than 1 year.

Ten of the tigers were photographed in more than one of the reserves, indicating their territories straddled the reserve boundaries. The authors conclude that each of the three reserves has a solid breeding tiger population and that, taken together, the HKK-TY landscape is a vital source of tigers that could potentially repopulate surrounding areas where they’ve been lost. This is supported by cases of known HKK-TY tigers dispersing into neighboring parts of WEFCOM and even across the border into Myanmar.

Conservation efforts pay off

Anak Pattanavibool, study co-author and Thailand country director at the Wildlife Conservation Society, told Mongabay that population models that take into account the full extent of suitable habitat available to tigers within the reserves and the likelihood that some tigers inevitably go undetected by camera surveys indicate there could be up to 140 tigers within the HKK-YT landscape.

Anak told Mongabay the tiger recovery is a clear indication that conservation efforts are starting to pay off. In particular, long-term action to strengthen systematic ranger patrols to control poaching as well as efforts to boost the tigers’ prey populations seem to be working, he said.

“Conservation success takes time. At the beginning we didn’t have much confidence that it would be possible [to recover tiger numbers], but we’ve been patient,” Anak said. For him, the turning point came in 2012, when authorities arrested and — with the aid of tiger stripe recognition software — prosecuted several tiger-poaching gangs operating in Huai Kha Khaeng. “These cases sent a strong message to poaching gangs and they stopped coming to these forests,” he said.

Although ranger teams have detected no tiger poaching in the HKK-TY part of WEFCOM since 2013, isolated incidents have occurred in peripheral parts of the forest network. In early 2022, for instance, authorities arrested five people and confiscated two tiger carcasses in Thong Pha Phum National Park in Kanchanaburi province, close to the border with Myanmar.

Effective law enforcement is paramount, Anak said. “The important point is to maintain the quality of the protection system. If something happened to undermine it, the situation could revert back to weak protection and poaching could start happening again.”

Such an eventuality would prove catastrophic for tigers and their prey. “When tiger poaching happens, it can happen quickly and quietly. So very suddenly, the tigers can disappear,” Anak said, adding that authorities should take the survey results as a sign to keep doing what it’s doing. “The budget, the number of park rangers and the patrolling system are all good just now. They are creating a stable situation for the tigers.”

Intensification of ranger patrols, in terms of both numbers of personnel and their coverage of the reserves, has helped tip the balance in favor of the tigers, Anak added. In 2007, ranger patrols typically encountered six or seven poaching camps per 1,000 km (600 miles) of foot patrols, he said, whereas now, they encounter just one or two.

Thailand operates the SMART (Spatial Monitoring And Reporting Tool) wildlife monitoring and antipoaching patrol method, a system that was honed over the years from elephant-monitoring protocols. Under the SMART system, ranger teams simultaneously collect wildlife field sign data while out on antipoaching foot patrols. It’s now implemented throughout the country’s network of protected areas and has been widely acclaimed for its capacity to help park managers pinpoint poaching and other human-related threats and adapt protection measures accordingly.

“The good thing about Thailand is that the government invests a big budget on forest protection and park rangers,” Anak said. He estimates the country’s protected areas are guarded by roughly 20,000 patrol staff, with 52 ranger stations in the HKK-TY landscape alone. “It’s quite a big force and its quite unique [in comparison to neighboring countries],” he said. “It’s like a green army to protect the forest and wildlife in Thailand.”

Harihar from Panthera said he agrees with the authors that law enforcement is vital to reduce poaching, which is by far the main threat to Southeast Asia’s tigers, he said. However, he added that it’s not possible to directly attribute the tiger recovery in the WEFCOM reserves to enforcement action.

“The law enforcement metrics evaluated [in the study] are broad metrics that indicate higher patrol coverage, effort, and detection of threats, but do not evaluate how the law enforcement program reduced the threat,” he told Mongabay in an email. He added that to learn lessons on how law enforcement can help restore tiger populations, more targeted evaluation studies are required.

Ungulate prey resurgence

Prior research has long linked the recovery of tiger populations to the presence of their prey species: large ungulates such as sambar deer (Rusa unicolor) and banteng (Bos javanicus) and gaur (Bos gaurus) wild cattle. A female tiger can have three to four cubs per year, but they can only survive if there’s sufficient food to eat.

Such large prey species are globally threatened, however, and fast disappearing from landscapes across Southeast Asia, including Thailand. Studies have concluded for years that even within well-protected, intact areas of WEFCOM, the tiger population can grow no further due to a lack of prey.

But evidence of healthy populations of several tiger prey species is beginning to emerge. In a separate new study, a team of Thai researchers including several of the same authors show that populations of sambar and banteng have more than doubled in recent years within Huai Kha Khaeng Wildlife Sanctuary. The authors attribute the recovery to antipoaching efforts and restoration of their key grassland habitats and water sources.

Surveys based on transect sampling and field sightings revealed that between 2007-2008 and 2021, the population density of sambar increased from two to four individuals per 100 km2, and banteng from fewer than one to two individuals per 100 km2. They also document that the density of muntjac deer almost tripled over the same time period. Meanwhile, wild pig and gaur densities remained stable.

Another recent study documents the first ever records of banteng dispersing out of Huai Kha Khaeng into the adjacent reserve, Thung Yai West. Taken together with previous evidence of their dispersal into Mae Wong National Park to the north, the authors say it’s clear that the banteng population in Huai Kha Khaeng is an important reservoir for repopulating the wider landscape and could in fact be home to the largest banteng population in the world.

“When we started this work in 2005, it was very hard to see banteng,” Anak told Mongabay. “But now, you can see herds of 30 or 40 of them in Huai Kha Khaeng. There is even a wildlife tourism project focused on them in the forest buffer zone.”

The ungulate recovery is also good news since scientists consider them proxies for wider ecosystem health. Recent research from Sumatra, for instance, found that sambar deer were consistently associated with a greater richness and diversity of other mammal species. Therefore, their recovery in WEFCOM might indicate a healthy overall system.

Connectivity for wider recovery

Sustaining the recovery of the growing population of tigers in HKK-TY will also depend on their ability to repopulate nearby areas from where they’ve disappeared. As wide-ranging and territorial species, tigers need extensive connected networks of safe forests that enable them to move across landscapes to maximize their genetic diversity and adaptability to climate change and other disturbances.

According to Harihar from Panthera, conservation actions at a sociopolitical level are required when it comes to boosting such connectivity. “Strengthening local economies and relying less on forest resources, avoiding infrastructure development in critical habitats and having policies that encourage compliance of nature-friendly land uses can be vital,” he said, adding that Thailand “has the right political will” to recover tiger populations on a wider scale.

While teams have sighted roughly 20 tigers in the Dong-Phayayen Khao Yai Forest Complex in the east of Thailand, close to the border with Cambodia, WEFCOM in the west is the hotspot of the country’s tiger recovery efforts.

Given the HKK-TY tigers will be a key source of animals repopulating empty forests in WEFCOM, Anak said he’s hopeful they can further boost the populations living there. He said he would like to see the tiger population density rise from its current level of roughly 3 tigers per 100 km2 to 5 tigers per 100 km2. “That would be about 350 tigers in this core part of WEFCOM,” he said.

At that point, tigers could not only repopulate other areas of WEFCOM, but also potentially move into suitable forests across the border in Myanmar, Anak said. The latest figures released by Myanmar authorities, in 2019, estimated the number of tigers remaining in the whole country at 22 individuals.

“Some NGOs set camera traps over the border in Myanmar, and they find some [tigers], but not in enough abundance to come into Thailand,” Anak said. “In reality, it will be the opposite situation, that tigers from here might be able to recover the tiger populations in Myanmar if the situation allows.”

Carolyn Cowan is a staff writer for Mongabay. Follow her on 𝕏, @CarolynCowan11.

Banner image: An adult male tiger in Huai Kha Khaeng Wildlife Sanctuary. Image courtesy of the Thailand Department of National Parks, Wildlife and Plant Conservation/WCS Thailand.

Citations:

Duangchantrasiri, S., Sornsa, M., Jathanna, D., Jornburom, P., Pattanavibool, A., Simcharoen, S., … Karanth, K. U. (2024). Rigorous assessment of a unique tiger recovery in Southeast Asia based on photographic capture-recapture modeling of population dynamics. Global Ecology and Conservation, 53, e03016. doi:10.1016/j.gecco.2024.e03016

Saisamorn, A., Duangchantrasiri, S., Sornsa, M., Suksavate, W., Pattanavibool, A., & Duengkae, P. (2024). Recovery of globally threatened ungulate species in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Global Ecology and Conservation, 53, e03012. doi:10.1016/j.gecco.2024.e03012 

Amorntiyangkul, P., Jornburom, P., Pattanavibool, A., Suksavate, W., Klanprasert, S., Kaewvisat, S., & Thongthai, T. (2024). First dispersal records of the endangered banteng (Bos javanicus) in Thung Yai Naresuan West Wildlife Sanctuary, Thailand. Ecology and Evolution, 14(6). doi:10.1002/ece3.11602

Phumanee, W., Steinmetz, R., Phoonjampa, R., Weingdow, S., Phokamanee, S., Bhumpakphan, N., & Savini, T. (2021). Tiger density, movements, and immigration outside of a tiger source site in Thailand. Conservation Science and Practice, 3(12). doi:10.1111/csp2.560

Jornburom, P., Duangchantrasiri, S., Jinamoy, S., Pattanavibool, A., Hines, J. E., Arnold, T. W., … Smith, J. L. D. (2020). Habitat use by tiger prey in Thailand’s Western Forest Complex: What will it take to fill a half-full tiger landscape? Journal for Nature Conservation, 58, 125896. doi:10.1016/j.jnc.2020.125896

Ardiantiono, Deere, N. J., Eka Ramadiyanta, Sibarani, M. C., Adhi Nurul Hadi, Noviar Andayani, … Struebig, M. J. (2024). Selecting umbrella species as mammal biodiversity indicators in tropical forest. Biological Conservation, 292. doi:10.1016/j.biocon.2024.110511

See related story:

‘Huge blow’ for tiger conservation as two of the big cats killed in Thailand

FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.