Researchers Trace the Evolution of Rhinos at Kaziranga National Park

Northeast India, part of the Indo-Burma biodiversity hotspot, hosts numerous endangered species at risk of extinction.

Within this landscape in the largest state in Northeast India, Assam, lies Kaziranga National Park, a UNESCO World Heritage Site that is a stronghold for megaherbivores, notably the Indian one-horned rhinoceros.

A study was conducted to examine the causes of the decline and current confinement of megaherbivores, particularly the Indian one-horned rhinoceroses in Kaziranga National Park. 

Scientists from the Birbal Sahni Institute of Palaeosciences, an autonomous institute of the Department of Science and Technology, used pollen samples from mud beneath wetlands in Kaziranga National Park to establish the first long-term palaeoecological records of palaeoherbivory in the park.

The researchers extracted a sediment core of just over a metre from the Sohola swamp within Kaziranga National Park.

Layer by layer, this mud acts like a natural archive, preserving microscopic traces of the past. Among these traces are pollen grains from plants and fungal spores that thrive on animal dung.

Fig: a. Location map of the sampling site, b. Vegetation coverage map of the Kaziranga National Park (after Das et al., 2014).

Based on fossil evidence, researchers discovered that the species was once widely distributed across the Indian subcontinent, but this distribution has since declined markedly since the Holocene.

The study (published in the journal, ‘Catena‘ (Elsevier)) highlights that Kaziranga’s present landscape differs markedly from its past and documents the regional extinction of megaherbivores, including the Indian rhinoceros, from northwestern India due to climatic amelioration during the late Holocene, especially during the Little Ice Age and increasing human activities.

In contrast, northeastern India remained relatively climatically stable, facilitating eastward migration and the eventual concentration of rhinoceroses in Kaziranga. 

Over the last ~3300 years, northeastern India remained relatively climatically stable with lower human pressure, while habitat loss, climate deterioration, and overhunting in northwestern regions forced rhinoceroses to migrate eastward and eventually concentrate in Kaziranga.

The study demonstrates how long-term vegetation and climate changes have shaped wildlife survival, migration, and extinction, providing long-term ecological knowledge to guide more effective conservation and wildlife management under present and future climate change.