Why The Rhino Survived In Kaziranga But Vanished Elsewhere

Long-term climate and vegetation stability is why the one-horned rhinoceros survived in north east India even as it vanished from much of the subcontinent.

Ancient wetland sediments explain why the one-horned rhinoceros survived in Assam while disappearing elsewhere in India

Hidden beneath the wetlands of the Kaziranga National Park, layers of ancient mud have preserved a detailed ecological archive stretching back more than three millennia.

A new scientific study shows that this long-term climate and vegetation stability is a key reason why the Indian one-horned rhinoceros survived in northeast India even as it vanished from much of the subcontinent.

The findings come from a pioneering palaeoecological investigation conducted by scientists at the Birbal Sahni Institute of Palaeosciences (BSIP), which reconstructed the first continuous record of past climate, vegetation and herbivore activity from within Kaziranga.

Wetland mud as a time capsule

To piece together Kaziranga's ecological past, researchers extracted a sediment core more than one metre deep from the Sohola swamp inside the park.

Each layer of mud acted as a natural time capsule, preserving pollen grains and coprophilous (dung-loving) fungal spores.

"Pollen tells us what kind of vegetation dominated the landscape, while fungal spores linked to dung give us indirect evidence of large herbivores such as rhinos," a BSIP scientist explained.

Using this method, the team reconstructed environmental changes spanning roughly 3,300 years.

Climate & Vegetation Stability

According to the study, Kaziranga did not always look the way it does today.

In its early phases, the region was dominated by denser forests and deeper swamp conditions, with relatively low megaherbivore activity.

Over time, wetlands became shallower and open grasslands expanded, creating ideal conditions for grazing animals, including rhinoceroses.

These transitions were driven by a combination of climate fluctuations, changing river dynamics, vegetation shifts and grazing pressure.

The research has been published in the international journal Catena.

Palaeoecological Study

Why rhinos vanished from the rest of India

The study also sheds light on why megaherbivores, including the Indian one-horned rhinoceros, disappeared from large parts of northwestern and central India during the late Holocene period.

Scientists link this decline to a combination of increasing climatic instability -- particularly during the Little Ice Age-- and intensifying human pressures such as deforestation, agriculture and hunting.

"In contrast, north east India experienced relatively stable climatic conditions and lower human disturbance," the researchers noted.

"This allowed rhinos to migrate eastward and eventually concentrate in areas like Kaziranga, where suitable habitats persisted."

3,300-Year Climate Record

Kaziranga, part of the Indo-Burma biodiversity hotspot and a UNESCO World Heritage Site, now supports the world's largest population of the one-horned rhinoceros.

Conservationists say the new findings offer crucial lessons for protecting megafauna in a warming world.

The long-term data show how climate stability and resilient habitats can act as refuges during periods of environmental stress -- insights that could guide future conservation planning, habitat restoration and wildlife management.

From Swamps to Grasslands

Supported by the Department of Science and Technology, the study highlights the growing role of palaeoecology in shaping modern conservation policy.

By looking deep into the past, scientists argue, policymakers can better understand how species respond to climate change -- knowledge that may prove vital as India faces increasing ecological pressures in the decades ahead.

Feature Presentation: Ashish Narsale/Rediff