Tarun Nair is a conservation biologist with an affinity for crocodilians and rivers. Leading the Wildlife Conservation Trust’s (WCT’s) Makara Programme, he works along North-Central Indian riverscapes that harbour the last remaining populations of the Critically Endangered gharial, a fish-eating crocodilian. To understand his work, Rizwan Mithawala spoke to him over email between boat surveys, power cuts and unstable internet. Here are some excerpts:
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A gharial female watches over hatchlings. Parental care is well-documented – hatchlings from several nests will aggregate in creches that are guarded by females and a large male over the first few weeks. Photo: Dhritiman Mukherjee.
Why are gharials so special?
The gharial can be described, simply, as a large, long-snouted, fish-eating, river-dwelling crocodilian endemic to the Indian subcontinent. And one just needs to take a look at a gharial, especially an adult male, to clearly see why it is both evolutionarily and ecologically distinct, although to some it can appear to be an oddly put together creature given the combination of characteristics!
More generally, crocodilian traits such as being amphibious, large, predatory, long-lived, and reaching high densities, allow them to play important roles as ecosystem engineers, indicators of ecological health, and as drivers of nutrient and energy transfer across ecosystems.
Where are they found, and what has happened to their population size and distribution over the past 100 years?
Historically, and even as recently as a 100 years ago, the gharial was widely distributed in the floodplain rivers of the Indus, Ganga-Brahmaputra-Meghna, Mahanadi-Brahmani, and Irrawaddy river basins, and quite possibly in the Godavari and Kaladan basins too. Going by accounts from British India, it was fairly common in much of its range.
By the 1950s and 60s, these populations were either depleted or extirpated, mainly because of hunting and fishing. Gharials were targeted by trophy hunters, skin traders, and by local hunters for meat and eggs. Trophy hunting and the trade in skins stopped in the early 1970s following the enactment of the Wild Life (Protection) Act, 1972, but the local egg consumption continued to be a threat, especially in the Terai region bordering India and Nepal. At the same time, large-scale construction of dams and barrages was responsible for range-wide habitat loss and degradation. Fishing took its toll too. In addition to accidental entanglements, fishermen and fishing contractors actively eliminated gharials. By the 1970s, the total gharial population in India was estimated at less than 200, with the species having shown a decline of almost 95 per cent in half a century. In response, the creation of Protected Areas and initiation of rear-and-release programmes under the Indian Crocodile Conservation Project helped reverse the population decline. This project was deemed a success by the mid-1990s and soon discontinued, only for the gharial population to see another phase of drastic decline between 1997 and 2006. There was also a mass mortality event between late 2007 and early 2008, which caused the death of over a hundred individuals in the Chambal.
A basking gharial is alerted by our survey boat. Regular surveys are essential to monitor gharial populations and habitats, especially since threats such as sand-mining and fishing are a constant menace for these crocodilians. Photo: Dr. Anish Andheria.
The 2019 IUCN Red List assessment for the gharial estimates a historic river length occupancy of over 20,000 km., and an inferred adult population >20,000 globally, but now occupying and numbering only a fraction of this estimate. They are currently extirpated from much of their historical range and persist only in a handful of sites, primarily in the Gangetic basin. Of these, the Chambal River (National Chambal Sanctuary) alone accounts for 80-85 per cent of the global gharial population. The remaining small, disjunct, breeding sub-populations include Katarniaghat National Park, Corbett Tiger Reserve and Gandak river in India, and Chitwan and Bardia National Parks in Nepal. The Son river produced two to three nests annually until recently, but has now lost all breeding males, while a couple of nests have been reported in the Mahanadi recently after nearly three decades! Other non-breeding, relict or reintroduced sub-populations exist in Ghaghara, Beas, Kosi, Hooghly, Brahmaputra, and Padma-Jamuna (Bangladesh) rivers.
However, there appears to be an increasing trend in the gharial population over the last 10 to 15 years, largely driven by recovering populations at two or three locations.
Tarun Nair leads the Wildlife Conservation Trust’s Makara Programme that is working to develop a conservation roadmap to secure gharial populations and riverscapes. Photo: Dr. Anish Andheria.
What is an ideal gharial habitat?
The gharial favours perennial rivers with deep pools and large sandbars. Deep pools serve as excellent refugia against threats and temperature extremes, and also provide ample feeding opportunities since fish (prey) congregate in these pools. Large sandbars are preferred sites for basking and nesting. And it certainly helps to maintain (near) natural flow regimes in these rivers to minimise breeding disruptions, and to keep in check anthropogenic threats and disturbances, particularly fishing, mining and encroachments. Large, contiguous, protected riverine habitats that can support multiple breeding groups and long-distance longitudinal movements are ideal, and currently only the Chambal meets these criteria, although constrained by several local and developmental pressures. All other gharial habitats are either too small or without formal protection, and support only relatively small or low-density populations at present.
What’s troubling them?
Several long-term, persistent and emerging threats impact gharial populations and habitats, and these multiple stressors often interact with one another to amplify their impacts. Major threats include dams; river regulation and flow diversion through barrages and lift-wells; fishing (gill netting, blast fishing, poisoning, electrofishing); river-bed mining for sand and stone; riverside agriculture and floodplain cultivation; pollution; and waterways development, and these threats impact gharials either through one or a combination of direct mortalities, habitat loss or degradation, flow disruption, prey depletion, and disturbances. Large infrastructural projects such as the proposed Inter-Linking of Rivers and National Waterways Projects can irreversibly damage gharial riverscapes through extensive habitat and hydrological modifications. Other overarching threats such as climate change and shifts in temperature and rainfall patterns can have implications on nest fates and hatchling sex ratios.
Forest staff and the WCT team navigating the rapids on the Chambal River during the 2023 annual survey of the National Chambal Sanctuary organised by the Madhya Pradesh Forest Department. Photo: Dr. Anish Andheria.
How does river regulation through dams and diversions affect gharial ecology?
The breeding adaptations of riverine fauna such as crocodiles, turtles, skimmers and terns reflect seasonal changes in water levels under natural flow regimes – nesting takes place in the dry season when low water levels expose sandbars, followed by hatching and fledging prior to the monsoonal floods inundating these nesting sites. River regulation through dams, barrages, and other such impoundments and diversions alter natural flow regimes and affect gharials and these other species in two major ways. On one hand, depleted dry season flow conditions decrease channel depth, increase channel braiding, and increase nest vulnerability to predation and cattle trampling; and on the other hand, random discharge of water from dams in the breeding season results in nest site inundation or erosion, often resulting in the complete loss of nests and eggs for that breeding season. Further, river regulation also impacts longitudinal and lateral river-floodplain connectivity, sediment transport, water quality, temperature and chemistry, and all of these can have cascading impacts on other upriver and downriver habitats and species – one obvious example being the disruption of cues that initiate the maturation and spawning of freshwater fish, many of which are themselves threatened and a vital component of riverine food webs.
An adult gharial basking at a nest site. Suitable nesting sites sans sand mining are at a premium, and even these are often subject to numerous disturbances such as riverside cultivation and livestock, as seen here, especially when accompanied by herders. Photo: Dr. Anish Andheria.
And fishing net entanglement? Can this be life-threatening?
Data on frequency of net entanglement is scarce, but this is definitely a major threat throughout their range. With their long, thin snouts, gharials, especially younger animals, are susceptible to getting entangled in fishing nets, and surveyors regularly encounter animals with nets clinging to or wrapped around their jaws. Older individuals may learn to avoid nets, but those that get trapped either drown or are killed intentionally by fishermen. Some animals that manage to break free still retain the nets, and may eventually starve to death. In some instances, fishermen resort to chopping or breaking gharial snouts to save their nets, and even these animals are no longer able to capture prey effectively, and lose condition and die.
So how is WCT’s Programme Makara making a difference? What are its objectives and core activities?
The Makara programme is working to develop a conservation roadmap to secure gharial populations and riverscapes. One component will involve an assessment of head-starting (a conservation strategy to minimise predation, wherein eggs are collected from the wild, hatched in captivity, hatchlings raised for about three years, and eventually released in the wild) and recovery programmes to improve population restoration outcomes, and also assess the feasibility of combining individual identification and remote monitoring tools to improve survey efficiency and coverage. The second component will attempt to characterise flow regimes and monitor key breeding sites to understand ecological flow requirements and minimise breeding disruptions, and facilitate threat reduction through mapping, capacity building and public engagement.
Your study sites harbour the last remaining populations of the species. Are they safe there?
Our study sites (the Chambal, Son, Ghaghara and Gandak rivers in the Gangetic basin) all experience varying types and levels of threats, and safety is therefore relative and dynamic across years and along the length of the river. For instance, the Chambal population is more susceptible to losing nests and nest sites to illegal sand mining, whereas the major challenge in the Son is from severely-reduced dry season flows leading to in-channel sedimentation and loss of connectivity. The Gandak and Ghaghara populations are outside the Protected Area network, and are therefore more dependent on the wide floodplains and braided channels as a buffer from local threats and disturbances, but this does not remove their vulnerability to nest site erosion owing to barrage flushing operations during the nesting season. Even within each site, locations closer to dams and barrages are more prone to sudden changes in water levels, while downstream sections may face higher fishing pressures.
Their long, thin snouts make gharials extremely susceptible to getting entangled in fishing nets, and many eventually starve to death being unable to feed. Photo: Dr. Anish Andheria.
How do you survey and ascertain whether nesting and hatching has been successful at a particular study site?
We are yet to start nesting surveys. But a simple, non-invasive method for coarse estimates would be to monitor potential nest sites at the start of the nesting season, keep track of trial nests, and then get an estimate of actual nests based on cues such as excavated sand and/or surface depressions accompanied by slide marks to and from the river, by observing attendant females, and manual excavations. Follow-up monitoring through the incubation period can help detect predation. Post-hatching, the nests are again checked for the proportion of successful hatched eggs, predations, and pre-hatching and post-hatching mortality. These can be further compared with the number of hatchlings observed at crèche sites adjacent to the nesting bank.
Are you engaging with other stakeholders as part of conservation, awareness and outreach activities?
The State Forest Departments are a major stakeholder, and we intend to assess and build capacity of frontline forest personnel in addressing ecological, management and legal aspects of conservation, to help improve site monitoring and protection, and achieve threat reduction.
Our public engagement efforts (communication, education and public awareness), specifically aimed at riverside communities and schools, will attempt to use audio-visual messaging through street theatre and/or social media to bring about behavioural changes such as positive action, positive inaction, and reduced hostility, through improved awareness and attitudes towards conservation. This is obviously easier said than done.
The Chambal supports the last viable population of the Critically Endangered red-crowned roofed turtle, but safe nesting sites are scarce even here, as sand mining often targets the best nesting banks. Photo: Dr. Anish Andheria.
How are your research insights going to impact policy and help plan conservation interventions?
These are still early days into the project, but we hope to provide practicable inputs towards improved Protected Area management and gharial population restoration outcomes. On the policy front, we’d like to address the provisioning of ecological flows in regulated rivers through dam reoperation and adaptive reservoir management, and reducing breeding disruptions through better inter-agency coordination.
Rizwan Mithawala is a Conservation Writer with the Wildlife Conservation Trust, and a Fellow of the International League of Conservation Writers.
