Gharials swimming across India-Nepal border an opportunity for enhanced co-operation

Gharial hatchlings at a new nesting site June 2020. Photo by Subrat Behera/WTI.

  • Transboundary coordination and better information capture and sharing through social media have helped researchers monitor the long-distance movement of gharials along the India-Nepal border.
  • Lack of uniformity in large-scale release of captive-bred gharials from the site of origin is one of the factors behind the transboundary movement of gharials.
  • Often gharials that are released into the wild and journey long distances are entangled in fishing nets and captured in rivers.
  • Experts have sought the release of captured gharials, protecting habitats that gharials could use for breeding and nesting, data sharing on the release of gharials, and better transboundary co-operation through a formal agreement.

School teacher Goutam Tantia recalls being shocked at seeing people put a price on glimpsing a gharial in a village in eastern Bihar, abutting Uttar Dinajpur district of West Bengal. 

“The eight feet-long female gharial was caught by locals in a fishing net from the Mahananda river which flows through Bengal and Bihar. Some of the local community members had kept it in a shallow water tank beside the river and did not want to let go of the animal. They were offering a peep at the gharial for Rs. 10 to Rs. 15. Many were poking at it with a bamboo stick,” Tantia, of the animal welfare group Uttar Dinajpur People for Animals, recounted his experience from October 2015. 

The gharial in Bihar was eventually rescued and brought to Bengal. “It was captured by the forest department and was placed in Rasikbill in Cooch Behar district in Bengal,” added Tantia, who facilitated the rescue.

Gharials (Gavialis gangeticus) are critically endangered and listed in the Convention of Migratory Species (Appendix I) with only about 650 adult individuals found in the wild in sparse pockets of the subcontinent’s rivers. Once common in the Indus, Ganga, and Mahanadi river systems, wild gharial populations are found mainly in India and Nepal. They are on the verge of extinction in Bangladesh. In India, the gharial nesting sites are now found mainly in Chambal, Girwa, Ghagra, and Gandak river basins.

The gharial that swam over a 1000 km across borders

This particular gharial that Tantia witnessed, had in fact had a transboundary run through the Gandak river barrage, straddling the Nepal-India border. It was released by Bihar Forest Department and Wildlife Trust of India at Valmiki Tiger Reserve as part of a gharial restocking project on the transboundary Gandak river (called Narayani in Nepal) earlier that year (2015). 

The individual moved upstream through the barrage, entering Nepal waters and subsequently swimming downstream. It was caught in the Mahananda river in east India, covering a distance of more than 1000 km in 234 days. Both Gandak and Mahananda are major tributaries of the Ganga river.

The 2015 long-distance gharial movement is among the seven recorded notable long-distance movement and/or transborder crossings by gharials in the last 40 years, highlighted in the IUCN Crocodile Specialist Group’s April-June newsletter. The most recent one is the identification and capture of a gharial that was released in Nepal and captured in West Bengal’s Hooghly river near Rani Nagar Ghat of Nadia District in May 2020.

As long-distance and transboundary movements of captive-bred gharials come to the fore, experts have called for protecting habitats that the fish-eaters pass through in their journey within the river systems and uniform release of the animals. They have also sought the release of gharials that were reared in captivity, released into the wild, and then placed back in captivity following their long-distance movement.

The gharial that was captured in the Hooghly river in May 2020. Photo by Somen Halder.

Transboundary coordination

There are around 10 marked gharials captured in various rivers of West Bengal in 2020. The origins of these indivduals are yet to be verified through examination of scute clipping patterns, said veteran crocodilian expert B.C. Choudhury. Tail scute markings are uniquely coded by gharial conservation biologists for monitoring of the released gharial in the wild.

Choudhury suspects that increasing transboundary gharial encounters are a result of the timing of large scale releases of the animals as part of captive-breeding efforts.

“As per the Crocodile Conservation Project guidelines, the releases are supposed to happen at the beginning of the winter (November-February) after the end of the monsoon season, when floods occur. By October the river waters would be cleaner and water levels recede and the movement of the animals will be restricted,” he said. 

“The other advantage of the release of the gharials in the wild in winter is because they are ectothermic (cold blooded) and their food requirement comes down in that season; so if you release them in winter, the fear of the animals dying of starvation will not be there. They will have time to adapt to their new surroundings,” Choudhury told Mongabay-India.

“But that regime is not followed by all release centers,” he rued, adding that when they are released slightly later than suggested, animals have opportunities to move downstream.

“Most projects are releasing gharials in the month of May and so immediately after the release, we have the flood season. A barrage or a dam is not really a deterrent to a gharial’s movement in the flood season, especially if it’s a barrage. And in the main stem of the Ganga, there are more barrages than dams. The animals upstream come down if it’s a barrage,” added Choudhury.

Ravi Kant Sinha, Chief Wildlife Warden, West Bengal said the rescued animals are kept in rescue centres which shields them from public and political pressure to put them on display for public. “We don’t give it to any zoo unless the rescue centre is far away. If we rescue gharials above the Farakka barrage, we release them then and there itself; after treatment, etc.”

Samir Sinha, who heads Wildlife Trust of India’s (WTI) Gharial Conservation Project on the Gandak river said because they are reared in captivity, dispersal could be one reason. “They could be exploring the natural habitat.”

Read more: Gharials of Gandak return, face development pressures

Observations from the Gharial Ecology Project, also known as the Gharial Telemetry Project, that was initiated in June 2008 to investigate the circumstances of the 2007-08 mass die-off of gharials in the lower Chambal river, showed that individual gharials show different patterns of seasonal movement and residency, primarily dependent on size/age. Adult females move as far as 80-120 km during each seasonal cycle to join dry season basking-breeding aggregations and to locate suitable nesting areas. In contrast, sub-adult gharials exhibit restricted movements, typically 10-30 km seasonally, and occupy seasonal residencies only 5-15 km in extent.

Nest-watcher and biologist taking out the hatched gharial eggs from a nest. By Subrat Behera/WTI.

Sinha said there are two reasons why the transboundary movements of the crocodilian species have received so much exposure and attention. “One is, better information capturing and sharing mechanism (social media, everybody is holding a camera in the form of mobile) and better coordination between researchers working on the species (data sharing between them), including Nepali counterparts.”

In May 2020, WTI field biologist Subrat Behera, who was also involved in ascertaining the identity of the 2015 gharial, came across a photo on social media of a gharial trapped in fishing nets in the Hooghly in West Bengal. “Based on the tail scute marking we could see it was released elsewhere. We contacted Nepal officials,” he said, adding that local communities often confuse gharials with crocodiles and are driven by fear to act negatively.

In Nepal, Bed Khadka of Gharial Conservation Breeding Center (GCBC) at the Chitwan National Park, was able to verify that the clipped tail scutes matched those of a gharial that had originated from the Center. The gharial was released upstream in Rapti River (a tributary of Narayani as Gandak is called in Nepal) and had journeyed about 1100 km from its release site. The animal is now in a rescue centre in Bengal and the forest department is working to get it to Bhagalpur in Bihar so it can be released back into the wild.

“The movement in March-May occurred prior to the rainy season, but the Narayani/Gandak river is a massive, glacier-fed river so there is sufficient flow of water to assist the gharial downstream, especially as the snowmelt begins upstream. The movement could have involved the gharial being passively carried downstream, or actively swimming,” said Khadka.

As of March 2020, 1515 gharials had been released from the GCBC into various rivers of Nepal, within the species’ geographic range. Khadka said both Nepal and India have “engaged in head-starting programs over long periods of time, and many, if not most, of the gharials released back into the wild, including areas upstream of this capture site in West Bengal, have been scute-clipped.”

Bringing back gharials through captive breeding

Choudhury explained that in the 1960s-1970s gharials were “almost nonexistent” in Indian rivers. But as conservation efforts started with Project Crocodile in 1975, they were reared and bred in captivity and put back in the wild in the 1980s and in the 1990s their population started picking up. 

While the National Chambal Sanctuary, which spans Madhya Pradesh, Rajasthan, and Uttar Pradesh, is the stronghold of gharial population, the transboundary Narayani-Gandak river system hosts the second largest population of this species. Chambal, Girwa, Ramganga, and Gandak rivers are the four extant breeding sites of the gharials in India.

Gharials reside exclusively in river habitats with deep, clear, fast-flowing waters and steep, sandy banks. Adult gharials prefer still, deep pools, formed at sharp river-bends and river confluence, and use sandy banks for basking and breeding.

Bihar state government is set to notify a 150-km stretch of the Gandak river as a Conservation Reserve, bringing that stretch under the protected area network. “Rivers are connected and the gharials in the wild may be moving through optimal habitat in a protected area. It is necessary to protect the habitat otherwise the good habitats will be destroyed due to human interference. We need to protect the breeding sites,” said Sinha.

“In a PA the entire area is not uniformly used by the animal. In Gandak, 80 percent of the habitat is suitable. Out of this, there are four key sites where they breed and we need to protect those. By including Gandak in the PA network you are ensuring a specific area is conserved,” he said, adding there are around 1800 to 1900 gharials in the Indian rivers.

A gharial kept in captivity. Tail scute markings are uniquely coded by gharial conservation biologists for monitoring of the released gharial in the wild. Photo By Partho Chatterjee
A gharial kept in captivity. Tail scute markings are uniquely coded by gharial conservation biologists for monitoring of the released gharial in the wild. Photo By Partho Chatterjee

The 2018 Aquatic Fauna of the Ganga River — Status and Conservation report prepared by the Wildlife Institute of India under the ‘Biodiversity Conservation and Ganga Rejuvenation’ project by National Mission for Clean Ganga (NMCG) revealed that the populations of the priority aquatic species, such as gharials and Gangetic river dolphin, were mostly restricted to the relatively undisturbed areas, including the PAs. These PAs account for around 15.5 percent of the total length of the Ganga river and the priority species were found to be distributed along about 50 percent of the surveyed stretch of the river. Therefore, restoration attempts must focus on these high-biodiversity areas, and conservation planning should be initiated in consultation with the stakeholder groups, the report suggests.

Bed Khadka also stressed the need to have a formal agreement between the two countries for transboundary cooperation, including timely updates on captured and released gharial and enhanced sharing of scientific information and meeting. “Transboundary protected areas encompassing rivers used by gharials will be important to protect gharials. Such transboundary protected areas will ensure that gharials are protected irrespective of which country they are and also when they take such a long-range voyage,” Khadka told Mongabay-India.

“In Nepal, we are now investigating the movement of gharials released from the GCBC, using radio-telemetry. Building on the data from the long-term scute clipping work and surveys, this study will provide a more detailed understanding of the movements of a subset of released gharials, including how often movements into India might occur,” he added.

Banner image: Gharial hatchlings at a new nesting site in June 2020. Photo by Subrat Behera/WTI.

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