Inside a shrinking stronghold
In the rugged forests of the Dong Phayayen-Khao Yai Forest Complex in eastern Thailand, a handful of Indochinese tigers are carrying tiny computers around their necks. Conservationists captured and fitted three adults with GPS collars in early 2025. The collars record hourly locations, letting researchers see where the cats hunt, travel, rest, and cross roads. The first downloads are unsettling. The cats are ranging across a vast landscape yet often stalking smaller prey than expected. One female, nicknamed Chantra by the field team, has even been documented taking hog badgers and opportunistic meals of soft-shell turtles and water monitors. In a country that has delivered the region’s most hopeful tiger comeback, the early data from these collars points to a population that is surviving, but not thriving.
Only 20 to 30 tigers remain in the 6,000 square kilometer complex. That is a fraction of the numbers seen in western Thailand, where tigers have increased for more than a decade. GPS fixes reveal a pattern that helps explain the gap. Instead of targeting large ungulates such as sambar deer, banteng, or gaur, the collared cats are often killing wild pigs and muntjac deer. Smaller prey fill bellies for a day but do not provide the steady energy a breeding female needs to carry cubs to term and nurse them. The prey profile points to a shortage of big animals, a known result of widespread snaring and illegal hunting in Southeast Asian forests.
The behavior of individual cats adds another layer of concern. Chantra, the female with a taste for unusual prey, is smaller than her sister. She also carries a kink in her tail. Field teams see these traits from time to time in isolated carnivore populations. They can be harmless quirks, but they can also hint at inbreeding in a group that no longer has enough fresh genes. With so few tigers spread across a large area, mates are hard to find, and movement is often constrained by highways and settlements. The collars now provide a way to map those constraints and to pinpoint the barriers that keep cats apart.
Why this forest is different from western Thailand
The contrast with western Thailand is stark. The Western Forest Complex (WEFCOM), a chain of protected areas along the Myanmar border, has become a rare success story. Scientific surveys place the tiger count there at 143 in 2023, up from 41 in 2007. Thailand now holds an estimated 179 to 223 adult tigers across the country. Most live in WEFCOM, especially around Huai Kha Khaeng and Thung Yai wildlife sanctuaries. Years of steady patrol work, arrests of poaching gangs, and recovery of large prey have created the conditions for a comeback. In recent years, government teams and partners have released sambar deer in key sites to rebuild the prey base, complementing natural recovery driven by patrols that cut snaring pressure.
WEFCOM also benefits from size and connectivity. The complex covers about 18,000 square kilometers, with 11 national parks and six wildlife sanctuaries that are managed in a coordinated way. Rangers use the SMART system to record patrol data and spot threats early. Camera traps, first deployed widely in 2007, provide a long record for each tiger. The result is a landscape where females have enough prey to raise litters, and dispersing young can find new territories within protected habitat.
A population stuck in place
Dong Phayayen-Khao Yai is a different challenge. The complex, which includes Khao Yai National Park and several wildlife sanctuaries near the Cambodian border, holds only a few dozen tigers across 6,000 square kilometers. That is a very low density for an apex predator that needs large prey and room to roam. Researchers, reviewing early collar data and carcasses found by patrols, report frequent kills of wild pigs and muntjac. Kills of sambar, banteng, or gaur appear less common. Biologists have long linked tiger reproduction to the abundance of these large ungulates. A mother that must make many small kills to feed herself will struggle to meet the energy demands of pregnancy and lactation. Cubs then face a tougher start, which slows population growth.
How the collars work and what they reveal
The GPS collars fitted this year add a new layer of detail to the picture. Each collar logs hourly positions, building a breadcrumb trail that can be downloaded when the team recovers the device. Plotting those points reveals resting sites, travel corridors, river crossings, and the edges of home ranges. When a cat stays in one small area for many hours, researchers can check the site for signs of a kill. When several bouts of feeding cluster in a valley or along a ridge, that area may hold more prey than surrounding forest. Over time, the data shows whether tigers avoid certain roads, risk crossing at specific culverts, or skirt settlements.
Movement studies in western Thailand, where dozens of tigers have carried GPS units, give a sense of what to expect. Analysts have used a time geography approach to distinguish different types of interaction when tiger ranges overlap. Mothers traveling with older cubs often show tight, concurrent movements before the young disperse. Neighboring females may show a pattern of avoidance, with encounters rare and brief. An adult male may travel along the borders of several female territories and alter his routes as those females shift their ranges. These patterns matter in a small population. If females avoid a valley because human activity has increased, their ranges can shrink or move into areas with less prey. If young males cannot find gaps to disperse, they remain near their mothers too long, which complicates breeding and can increase conflict.
A diet of small game, and why that matters
In most of Asia, a healthy tiger diet centers on large ungulates. Sambar deer, banteng, gaur, and large wild boar deliver the calories and protein that make regular reproduction possible. The collars in Dong Phayayen-Khao Yai point to a different menu. Field checks and camera images associated with GPS clusters show kills of wild pigs and muntjac deer again and again. The female Chantra has a broader list, including hog badgers and opportunistic feeding on soft-shell turtles and water monitors. That mix is unusual for wild tigers in Thailand. The shift to smaller prey has a cost. A hunter that specializes in small animals must kill more often, which means more travel and more risk of injury. It can also bring tigers closer to people, since wild pigs raid crops and muntjac browse near forest edges.
For managers, the message is clear. Where prey is abundant and protected, tigers recover. Where prey is scarce, they stagnate. Western Thailand shows what can happen when ungulates rebound. Patrols that target snaring and a program to breed and release sambar have helped rebuild a food base, and tigers have followed. The same approach can guide work in the east. The collar data tells patrol leaders where tigers spend time, which valleys still hold small herds, and which areas are quiet. It can also reveal gaps where snaring or hunting has emptied the forest of big animals. Those maps can focus law enforcement and inform decisions about where to restore habitat and, if needed, where to consider careful prey releases.
Genetic warning signs in a small population
Small, isolated populations face a second threat beyond food. With few mates to choose from, related animals are more likely to breed. Over time, rare, harmful genes can become more common and health problems appear more often. Researchers in Dong Phayayen-Khao Yai are alert to that risk. Chantra’s kinked tail and smaller body size than her sister are the sort of field clues that keep geneticists cautious. A single trait does not prove inbreeding. Yet when numbers are this low, the risk is real, and every barrier that limits movement makes it worse. Gene flow requires tigers to move, and movement requires connected habitat.
Fragmentation is now the central challenge in many parts of Southeast Asia. Highways slice through forest blocks. Construction sites, quarries, and power lines cut access to water and force animals into narrow strips that lack cover. Proposed dams can flood river valleys that serve as natural corridors. Each feature may seem small on a map, but together they shape where animals can live. For wide ranging predators like tigers, the result is a patchwork of safe zones and traps. The GPS collars will help planners see which highway crossings get used, where fencing is needed, and which culverts can be modified so animals avoid tracks and lanes.
Connecting forests and reducing risk
There are proven fixes. Wildlife overpasses and underpasses that match natural travel routes can cut roadkill and reconnect ranges. Fencing that funnels animals to those safe passages reduces the chance of collisions. In key valleys, restoring native vegetation along streams creates shade and cover that prey seek, which brings predators back to safer interior areas. The case for these investments is strongest when data shows exactly where cats choose to cross. Collars can also identify stepping stone habitats, the patches of forest that let animals move between reserves without entering farms or towns. As agencies plan transport and energy projects, the data will help adjust routes and schedules to reduce risk to wildlife.
The role of prey recovery and patrols
Thailand’s progress in the west rests on two pillars, strong protection and a richer prey base. Government agencies and partners have rebuilt herds of native ungulates, including sambar deer, in core sites. Patrol teams, backed by technology and training, raised the cost of poaching. Countrywide, an estimated 20,000 staff guard protected areas. In the Huai Kha Khaeng and Thung Yai landscape alone, 52 ranger stations coordinate patrols. A crackdown on tiger poaching gangs in 2012 marked a turning point, and since 2013 no tiger poaching incidents have been detected in the core of that landscape. These gains have allowed tigers to breed and spread within WEFCOM.
Stuart Chapman, who leads the WWF Tigers Alive Initiative, cautions that progress depends on keeping threats low when numbers are small. He said the stakes are high in landscapes like Dong Phayayen-Khao Yai.
Every tiger counts, particularly when populations get to such low levels that recovery then depends on no additional threats coming in that can potentially wipe them out.
Anak Pattanavibool, Thailand country director at the Wildlife Conservation Society, points to patience and steady law enforcement as the engine of recovery in the west. He noted how difficult the early years were, and why an unbroken protection system matters.
Conservation success takes time. At the beginning, we did not have much confidence that it would be possible to recover tiger numbers, but we have been patient.
Technology and training make a difference
Thailand has invested in tools that guide patrols and help managers adapt. The SMART platform standardizes how rangers record tracks, snares, and signs of illegal activity. GPS units carried by patrols confirm coverage and reveal gaps. Cameras record the individual stripe patterns that identify each tiger, creating a database to track births and survival. At Huai Kha Khaeng, a regional training center teaches rangers how to use GPS, cameras, and data to plan patrols and monitor prey. In buffer zones, CCTV has helped catch poachers and seize weapons. These systems matter in the east as well. Combined with collar data, they can map the places where patrol pressure should increase, where snares concentrate, and where big prey still eke out a living.
What success could look like in the east
The early findings from Dong Phayayen-Khao Yai provide a checklist for action. First, boost the food supply. That means strict removal of snares, stronger prosecutions for illegal hunting, and habitat work that supports sambar and other large ungulates. Where natural recovery stalls, managers can evaluate carefully planned releases of native prey, as seen in western Thailand. Second, maintain patrol coverage at a level that deters poachers before they enter the forest. Third, use the collar maps to guide infrastructure fixes, from fencing and culverts to full wildlife crossings, and to redesign risky road sections. Fourth, invest in community programs that reduce conflict, such as support for fences that keep wild pigs out of fields, stalls that secure livestock at night, and ecotourism that rewards villages for healthy wildlife. Finally, prepare to swap data and strategies with neighboring reserves, so that future dispersing tigers can move safely into new habitat.
The team managing the collars plans a full threat analysis, including poaching, snares, and the effect of highways and proposed dams. Those results, coupled with movement and diet data, can guide funding to the places where it will do the most. Thailand has already shown that tiger recovery is possible at scale. If prey returns and movement becomes safer, the small population in the east can grow. The GPS data now streaming from these cats offers a rare, concrete guide to where each step should happen.
At a Glance
- Three tigers in Dong Phayayen-Khao Yai were fitted with GPS collars in early 2025, a first for this population.
- Hourly location data show frequent hunting of wild pigs and muntjac, a shift from larger prey.
- One collared female, Chantra, targeted hog badgers and opportunistically fed on soft-shell turtles and water monitors.
- Researchers suspect a shortage of large ungulates, which can limit tiger reproduction and survival.
- Physical markers such as a kinked tail and small body size raise concerns about inbreeding.
- The forest holds only 20 to 30 tigers across about 6,000 square kilometers.
- Western Thailand offers a model, with tigers tripling since 2007 after stronger protection and prey recovery.
- Thailand now hosts an estimated 179 to 223 adult tigers, the last viable Indochinese tiger stronghold.
- Conservation teams plan threat analysis for poaching, snares, and habitat fragmentation from roads and potential dams.
- Ranger patrols, SMART monitoring, and potential prey releases are central to plans for recovery in the east.
