After more than six decades of absence, the Asiatic wild ass — known in Mongolia as the khulan — is back in eastern Mongolia. Hundreds of the animals have been recorded crossing the Trans-Mongolian Railway and recolonizing habitat they had not reached since the mid-20th century, in what researchers are calling the first confirmed evidence of khulan recolonization within their historical range.
At a glance
- Khulan recolonization: A new study published in the journal Oryx confirms that khulan are now being seen repeatedly in several groups east of the Trans-Mongolian Railway — a barrier that had blocked their movement for decades.
- Safe passage zone: In May 2025 C.E., the Wildlife Conservation Society and Mongolian government partners officially designated a monitored, fence-free passage corridor near the China-Mongolia border, giving the animals a clear route across the railway line.
- Global significance: Mongolia’s Gobi region holds roughly 91,000 khulan — more than 84% of the entire global population — making every successful habitat reconnection effort critical to the species’ long-term survival.
What the railway took away
The Trans-Mongolian Railway cuts through one of the world’s most important grassland ecosystems. For migratory species like the khulan, that kind of linear barrier is not just inconvenient — it can be fatal to a population’s long-term health.
The khulan is a wide-ranging animal. It depends on connected, open steppe to reach seasonal grazing areas and water sources as Mongolia’s harsh, variable climate shifts across the year. Fencing along the railway severed that movement, cutting eastern habitat off from core populations in the south and west. Over time, the eastern range was simply emptied out.
Habitat fragmentation like this is one of the central challenges facing large mammals across Central Asia. When a species can’t move, it can’t adapt. Populations shrink, genetic diversity narrows, and local extinctions follow.
How the corridor was built
The recovery began with a practical experiment. Teams from the Wildlife Conservation Society (WCS) and their Mongolian government partners tested temporary fence-free stretches along the railway to see whether khulan would use them — and whether train safety could be maintained.
The results were encouraging on both counts. Monitoring showed wildlife crossing the railway without a measurable increase in train collisions. That evidence gave the project the credibility to move forward.
In May 2025 C.E., the partnership officially set aside a monitored safe passage zone near the China-Mongolia border. Cameras and survey teams tracked the results. Hundreds of khulan were subsequently recorded on the eastern side of the railway — including crossings during winter, when the need for connected habitat is most acute.
“Documenting khulan crossing this long-standing barrier and beginning to re-establish in their former range represents an extraordinary conservation breakthrough,” said lead author Buuveibaatar Bayarbaatar, per the WCS Newsroom.
A broader win for Mongolia’s steppe
The khulan is not the only large mammal to have been brought back to Mongolia through deliberate conservation work. Przewalski’s horse — known to Mongolians as the takhi, and the only equine species never domesticated — was successfully reintroduced after going extinct in the wild. In 2023 C.E., a Spanish nonprofit moved 16 Przewalski’s horses from Mongolia to the Iberian Peninsula, where they have since begun reshaping the local landscape.
These projects share a common insight: restoring species requires restoring the connections between places. A single protected area is rarely enough. What large, migratory mammals need is landscape-level thinking — corridors, not just sanctuaries.
For the grasslands of eastern Mongolia, the return of the khulan matters beyond the species itself. Connected landscapes are more resilient landscapes. Healthy steppe supports the herders, livestock, and communities that have depended on it for centuries.
What comes next
The study’s authors are clear that the work is far from finished. The khulan still faces serious pressure from habitat fragmentation, competition with livestock, illegal hunting, and a warming climate that is making Mongolia’s already extreme seasons more unpredictable. The species is classified as Endangered on the IUCN Red List, and eastern Mongolia’s recolonized habitat remains fragile without formal protection.
Plans are underway for a local protected area on the eastern side of the railway that could help preserve the gains already made. The study calls for continued strategic investment in wildlife-friendly crossings and habitat restoration east of the railway to support further recolonization and reduce pressure on core populations in the South Gobi.
The research also establishes a critical baseline. Before this study, there was no confirmed evidence that khulan were returning to their historical eastern range at all. Now there is — and that evidence can guide funding, policy, and infrastructure decisions for years to come.
It’s a reminder that the relationship between infrastructure and wildlife need not be one of permanent conflict. With the right partnerships and the political will to act, a railway that once divided a species from its habitat can become part of the story of its return.
Read more
For more on this story, see: The Cool Down — Asiatic wild ass returns to Mongolia after 65 years
For more from Good News for Humankind, see:
- Alzheimer’s risk cut in half by drug in landmark prevention trial
- Renewables now make up at least 49% of global power capacity
- The Good News for Humankind archive on Mongolia
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