In my previous articles, I introduced the Chambal Nature Sanctuary and the work being done by American Scientist Dr. Jeffrey Lang with his local Indian counterparts in a long-term study of the critically endangered Gharial. I continue with my discussion with Jeff on the work that is ongoing for the study of the ecology and behaviour of Gharials.
Jeff explained that Gharials have some parallels in their life cycle to humans. They do not become sexually mature until they are in their teens and a female will reproduce at the rate of around 40 eggs a year until she is in her 40s or 50s. The National Chambal Sanctuary in Northern India has the world’s largest free-living population of Gharials and an estimated 2,000 of the total wild population of 2,500 in the world. I asked if this was driven by the Chambal River being the cleanest river in North India. Jeff wholeheartedly agreed that the Chambal was special, particularly "clean" compared to other Indian rivers, but also unimpeded, with no dams or barrages, except in its headwaters. However, the radio telemetry work and the GPS data downloads were revealing that in the National Chambal Sanctuary, adult female Gharials were able to make long distance movements of a magnitude that had not been appreciated before. The gharials' requirement for an open river system is shared with other endangered wildlife such as the South Asian River Dolphins, large river turtles, and big species of river fish. I would undertake three river safaris to see more of the mighty Chambal River and its riverine animal residents.
I learned two types of data loggers were in use. I had noticed one type, VHF transmitters, on my first river safari. The small radios were attached to the tails of gharials, just behind the legs, and sent out beeping signals that could be detected with special radio receivers. This required researchers to patrol the river, typically on a boat (but also on foot), using a five element directional Yagi antenna and receiver. Each transmitter has a unique signal allowing the individual to be identified. However, this method is not perfect as the signal range is limited, to four to five kilometres. If the researchers go in one direction and the animal has gone in another, it will not be picked up at all. Significant movements by the animals can be missed by the movements of the researchers and the animals not coinciding. This became all the more apparent when some of the animals were also fitted with a second type of transmitter that also logged location information via GPS. These units are more sophisticated and can be calibrated to capture and store GPS points multiple times each day. These GPS loggers also transmit a VHF signal which enables manual tracking but the VHF signal is less powerful. The beauty of these loggers is that the data they have stored can be downloaded remotely using UHF signals without needing to catch the animal, or via a satellite link to the Internet. If the animal is within a few hundred metres and the signal is good, the research team can use their antenna, receiver and software on a laptop to download the GPS datapoints.
The GPS loggers also result in better year-round monitoring of movements and to a finer scale. With the manually tracked VHF transmitters, the data is better during the dry season (November to February) when the Gharials are basking in the sun on land. During the monsoon months (July to September), the data capture is limited because the gharials are mostly in the water. The GPS logger data that has been downloaded has come up with surprises. One of the tagged subadults had occupied a stretch of river that had been monitored but had gone undetected for nine months based on the manual tracking from its VHF transmitter. But its presence in the area being monitored was revealed by its GPS data.
The combination of the radio telemetry from manual tracking and GPS downloads has been revealing a fascinating picture. Most juveniles and subadults are fairly sedentary, with their movements restricted to around a 10-15 km stretches of river. Adults on the other hand, often make long distance movements between their upriver nesting sites and the downriver locations close to the Chambal Yamuna confluence. The data loggers are supplemented by two more methods to understand their behaviour, especially the parental behaviour. One is visual observation, done at a distance to avoid adversely impacting the behaviour of animals. Highly visible coloured discs have also been attached to the tails to enable visual identification of radio-tagged individuals.
The second was the use of infrared “game cameras” which can capture near continuous video clips at 55 second intervals. Gharials nest using an unusual creche system where multiple females, sometimes as many as 40 plus individuals lay eggs in nests which are clustered in colonies, like some bird species. At some sites, more than 30 nests are found together and may produce more than a thousand hatchlings all in one place. The hatchlings arrive within a week to ten days which means the breeding, egg laying and hatching are synchronised. Adult males maintain a breeding arena where females have suitable sandy slopes in which to build nests close to each other, sometimes only a metre apart. The hatchlings are vocal even in the egg and when they are ready to emerge, the females open the nest. However, another feature that sets the Gharials apart from other crocodilians is that the females do not carry the hatchlings to the water. The hatchlings walk down to the water by themselves and stay together in a creche. Jeff wryly noted that one reason for that may be that the jaws of the female Gharials are lined with over 100 sharp teeth. The teeth are evident in some of my images accompanying this series of articles.
The nests and the new hatchlings are typically guarded by a single dominant female. Work is still underway to understand the dynamics with other nesting females. The dominant female guardian is accompanied by a male guardian, typically a young mature male with a prominent ghara, but not necessarily the male parent. However, in some instances, the dominant breeding male will also be the male guardian. However, Jeff explained that they have recorded other instances where the dominant guarding male was not the dominant breeding male, but a junior male likely apprenticing to be a future breeder. In this way, he can become familiar to reproductive females who may choose him as a good prospect to be a future mate.
The researchers also came across one situation where a larger male had arrived and driven away from the previously dominant breeding male. The newly arrived male had acted as the dominant nest guardian. But he had arrived on the scene too late and the young that had hatched had probably been sired by the previous male. When the hatchlings are in danger, the guardian male will make his presence clear with loud jaw claps and also with hissing noises produced by exhalations which resonate in the cartilaginous ghara. Jeff and his team have been studying such parental as well as alloparental behaviour at these gharial nest sites for several years now. Being a helper may be one way in which animals learn parenting by helping to bring up a related brood. Such helping behaviour is performed by close relatives, or alloparents. Jeff chuckles at the thought of palaeontologists using such alloparenting behaviour performed by Gharials as a reference to suggest that dinosaurs were not only caring parents, but possibly alloparents on occasion. However, he cautions that it may not be so simple. They have observed subadult Gharials approaching the nest colonies and snatching baby Gharials. Cannibalism may arise from the need to grow fast. This is especially important for the males who need to put on bulk if they are to later become a dominant breeder.
The data recorded has thrown up other surprises. One female travelled 210 km downriver to the Chambal-Yamuna confluence where she spent the monsoon season. During the monsoon, the confluence is especially rich in food because of the nutrient flow. For nesting, she had travelled back over a 100 km upriver. Thus during the course of a year an adult female may travel over 300 km, and then she does this year after year, for several decades. This reinforces why the long-term conservation of species such as the Gharial needs a coordinated effort spanning multiple states and across fairly large spatial scales, across the riverine landscape with an expansive regional watershed. This is known as a regional approach to conservation and one frequently hears of this scenario for wide-ranging animals such as elephants which require adequate corridors connecting protected areas in a terrestrial landscape. Rivers, themselves, are also important corridors for similar movements in aquatic landscapes, where animals require different kinds of habitats in different seasons, and/or for different purposes, and feeding versus reproduction.
Jeff works with local counterparts and employs local staff who conduct the monitoring year-round in what is known as the Gharial Ecology Project which is under the auspices of the Madras Crocodile Bank Trust, a South Indian based NGO. The project brings together many people under the umbrella of collaborative Gharial Conservation with related projects elsewhere in India and Nepal. Jeff understands that it is important to give recognition to the locals who are engaged in the study. With this in mind, researcher Pankaj Kumar is listed as a co-author in the papers the project has published. The remit of the Gharial Ecology Project is not confined to just the scientific field work. Their activities encompass a wide range of stakeholder engagements. They conduct training camps for Forest Department frontline staff from the three states bordering the Chambal. They also have a school outreach programme to educate teachers and schoolchildren. They also need to educate the larger Indian conservation community on the threats to the long-term survival of these animals from human-induced threats such as industrial scale sand mining which continues although it is now banned under the law.
Subsequent to my visit, I heard from Jeff that in 2017, he and his Indian colleagues were able to survey the whole of the Chambal National Sanctuary, 425 km from Pali near Ranthambore down to most downstream nests near Chikni Tower, about 50 km upstream from the confluence with Yamuna. They found 411 nests, 356 of which hatched and produced an estimated 40 hatchlings per nest. This equates to an encouraging 16,000 hatchlings for the year in 2017. Furthermore, they conservatively estimate they had actual counts of around 500 mature adult Gharials in the last several years. Similar levels of nesting have been documented by the field team during 2018 through 2020.
The research and conservation model which I saw in the National Chambal Sanctuary is a good one. A collaboration between local scientists and foreign researchers like Jeff Lang can be productive, providing for improved access to international funding and valuable training experiences, in the country as well as abroad. It provides opportunities for local researchers to work with recognised experts who have experience in using cutting-edge technology and methods across different countries. All of this is contributing to Indian science and helping a team of passionate Indian conservationists to secure a future for a very special animal.