A population reborn
Manas National Park, a UNESCO World Heritage site at the foothills of the Himalayas, once had a thriving population of over 100 greater one-horned rhinos (Rhinoceros unicornis). That changed in the late 1980s and 1990s when civil unrest engulfed the region. The park became inaccessible to authorities, and poaching ran rampant, leading to the complete local extinction of its rhinos by the early 2000s.
The restoration of peace in 2003 prepared the way for one of India's most ambitious conservation efforts. In 2005, a coalition including the Assam Forest Department, the International Rhino Foundation, and WWF-India launched the Indian Rhino Vision 2020 (IRV 2020). The program's goal was to establish a new, viable rhino population in Manas to spread the risk for the species, which was heavily concentrated in Kaziranga National Park.
Starting in 2008, the program began moving rhinos. Over the next several years, a total of 22 adult rhinos were translocated from the crowded grasslands of Kaziranga National Park and Pobitora Wildlife Sanctuary to Manas. Twenty orphaned or injured rhino calves were hand-reared at the Centre for Wildlife Rehabilitation and Conservation and later released into the park. The project was a success: by 2021, the new population had grown, with 38 calves born in their new home.
Genetic bottleneck to genetic treasure
The success of the reintroduction is a numbers game. It represents a unique, real-time example of evolutionary dynamics. A recent genetic study revealed an unexpected and scientifically significant outcome. The small founding group of rhinos moved to Manas happened to carry specific mitochondrial DNA (mtDNA) haplotypes—sets of genetic variations—that have since disappeared from the much larger source population in Kaziranga.
This phenomenon is a consequence of genetic drift, where random chance can cause gene variants to be lost in a population over time. By moving a small subset of individuals, the IRV 2020 program inadvertently created a genetic snapshot. The Manas rhino population now acts as an important reservoir of genetic diversity that no longer exists in its parent population. One study confirmed that the reintroduced Manas population has a higher variation in its mitochondrial DNA compared to other rhino populations that were re-established from a single event.
This outcome demonstrates how a local extinction, followed by a carefully managed reintroduction, can lead to the formation of a genetically distinct population. The rhinos in Manas are a conservation success; they are an ark, preserving lost alleles and providing a buffer for the long-term survival and adaptability of the entire species. The process has, in effect, used a local extinction to create a new evolutionary trajectory.