Among the largest and most endangered crocodilians in the world, the gharial (Gavialis gangeticus) is on the verge of extinction today. This harmless fish-eating crocodile has fewer than 200 adult breeding individuals in the wild, their numbers having plummeted rapidly over the past few decades due to destruction of their riverine habitats, entanglement in fishing nets, and hunting. But among this gloom and doom, conservationists have been working tirelessly to reinstate the wild populations.
In one such attempt in April this year, a team from the Wildlife Trust of India (WTI) and Bihar Forest Department released six satellite-tagged gharials into a stretch of Gandak River (a tributary of the Ganges) lying between Valmiki Tiger Reserve and Sohagi Barwa Wildlife Sanctuary. The six individuals included five adult females and one male, bred in captivity at the Sanjay Gandhi Biological Park in Patna (or Patna Zoo).
“It was a great moment to see the captive bred animals going back to the wild, from a small pond at the Patna Zoo to the clean fast flowing river Gandak,” said Samir Kumar Sinha, WTI’s regional head for Bihar. “Interestingly, in India, captive breeding of gharials started with some eggs collected from the Narayani or Gandak river. The release of captive bred gharials in the same river, thus, makes the cycle complete.”
Satellite-tagged gharial released in River Gandak. Photo: Samir Kumar Sinha/WTI.
While the gharial population in the wild has remained low, it has been rising fairly rapidly in captivity. To restock the dwindling wild crocodile populations, the Indian government together with the United Nations Development Program-Food and Agriculture Organization (UNDP-FAO), launched a Crocodile Breeding and Management Project in 1975. It was under the aegis of this project that numerous rehabilitation centres were set up for gharials, and other crocodile species. Several thousand gharials were reared in captivity in these centres, and released back into the wild. Subsequently, the project was declared a success.
In 2006, however, surveys revealed otherwise. With less than 200 mature breeding gharials in the wild, their IUCN status was soon changed from Endangered to Critically Endangered. Despite a successful captive breeding program, the restocking of wild populations has yet to prove as effective.
Satellite-tagging of gharials and their continued monitoring after release could, however, help conservationists better understand their movement, habitat use, and ability to adapt in the wild.
WTI team and forest department staff with a satellite tagged gharial near river Gandak. Photo: Neha Sharma/WTI.
“The tagged animals would be satellite tracked for the next 12-18 months (based on the life of the battery in the transmitter). Other physically marked animals would be tracked manually,” said Sinha.
But for the gharials to survive in the wild, various lingering threats need to be addressed urgently. B.C. Choudhury, a senior advisor to WTI and the Regional Vicechair of the IUCN Crocodile Specialist Group, told mongabay.com, “While restocking is an active conservation action, there are lots of other disturbing causes that need to be eliminated from the riverine habitat of gharials. These include maintaining an optimal ecological flow in the rivers, stopping illegal and destructive fishing, as well as agriculture, and sand mining along the river banks that are the egg-laying areas of the gharial and many other aquatic fauna.”
For now, the six released gharials have traveled more than six miles (10 kilometers) from their release site, and have been spotted basking on the sandy river beds very close to other wild gharials in the river, according to Sinha. The team plans to continue to release gharials in the river after the monsoons.
“This will help us compare the adaptability and movement patterns of the gharials pre-and post-monsoon,” said Choudhury. “This in turn will give us an insight into our plans of initiating a similar exercise for the gharials in Bhutan, which have a sizable population in captivity, and require urgent attention for release to the wild.”
A captive Indian gharial (Gavialis gangeticus). Photo by Matěj Baťha/Creative Commons 3.0.
Satellite-tagged gharial released in River Gandak. Photo: Samir Kumar Sinha / WTI.
WTI team satellite-tagging gharial (Gavialis gangeticus) at Sanjay Gandhi Biological Park, Patna. Photo: Neha Sharma/WTI.
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Captive gharial. Photo: Justin Griffiths/Public Domain.
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