Discovery of new gharial population
The Gharial (Gavialis gangeticus), endemic to the Indian subcontinent, has been classified as Critically Endangered by IUCN on the basis of a precipitous decline in distribution and abundance, as well as only a remnant global population (IUCN 2007). The National Chambal Sanctuary (NCS) in India holds the largest population of Gharial, estimated at >80% of the remaining world’s wild Gharial, with much smaller populations in Katerniaghat Wildlife Sanctuary on the Girwa River, in Chitwan National Park (Nepal) on the Narayani River and on the contiguous Gandak River in India, and in Corbett National Park on the Ramganga River. >90% of annual nesting recorded globally occurs in the NCS. After an initial and slow recovery in the late 1970s-early1990s, the NCS population has undergone two sharp declines, one in the decade prior to 2005, and the other in 2007-2008, followed presently by evidence of a robust recovery of the only open-river, self- sustaining Gharial population still extant.
The surveys were carried out in 2015-2017, with each survey focused on a specific objective.
The Chambal is a clear and fast- flowing river that originates from the Vindhya hill range, in central India. A 618-km stretch of the Chambal River, between Jawahar Sagar Dam and Panchhnada, which is protected under NCS, receives water from the mainstream and additionally from Parvati, Kali Sindh and Banas Rivers, where the main study area lies, at the border of Madhya Pradesh and Rajasthan.
Climatically, the region lies within the semi-arid and sub-humid region of India. Moderate rainfall, high temperatures, dry summers and cold winters are the main features of climate.
The 2015 survey was conducted on all three rivers, to assess the potential of each for the presence of either Gharial and/or Mugger. In winter (December-February), animals were detected basking, and in summer (June) nests and/or hatchlings were evident. Survey routes were plotted on digital maps of each river.
The sex of observed Gharial was also recorded in the survey, classifying them as ‘males’ based on a clear protuberance at the tip of the snout, females/ sub-adults for large individuals lacking such a protuberance, and juveniles for smaller size classes. The intensity of human activities along the river banks was recorded as well throughout, notably net fishing, water extraction and sand mining.
In brief, Gharial and Mugger were present only in the main channel of the Parvati River at any appreciable distance upstream from the confluence of all three rivers. In addition, breeding adults, nests and hatchlings were observed upstream in the Parvati, but nothing comparable was found in the other rivers. The Banas River has records of seasonally isolated individuals; the Kali Sindh River lacked Gharial and had Mugger only a short distance upstream from its confluence with the Chambal. Consequently, the Kali Sindh was excluded after the initial survey, and the Banas was monitored through rescue operations and local reports.
In the initial 2015 survey along the Parvati River, 14 Gharial were encountered between Pada Ghat and Koth. On the Banas, only one Gharial was observed near Banas bridge, 14 km from the Chambal confluence; and no Gharial was found on the Kali Sindh River. In 2016, 5 Gharials were reported in the Banas River near Aamlideh – 1 was rescued and 4 were noticed alongside by the Rajasthan Forest Department.
Based on these findings, we focused primarily on the Parvati River in subsequent surveys. In 2016, 29 Gharial (1 male and 28 females/sub-adults) were observed from Pada Ghat to Rondi (~40 km). The presence of a male Gharial at Jind Baba along the Parvati River (~ 38 km upstream; within the NCS) prompted us to investigate signs of nesting. In June 2017 another survey was conducted at Jind Baba and Mor Kudna area (~30 km upstream), in which 1 male and 3 females/ sub-adults along with 203 hatchlings were spotted at Jind Baba; in addition, 2 females/sub-adults along with 42 hatchlings were sighted at the Mor Kudna area. Based on an average clutch size of 35-45 eggs/nest, these observations indicate the presence of 4-6 nests at Jind Baba, and possibly an additional 1-2 nests at Mor Kudna. The upstream boundary of the NCS on the Parvati is at ~60 km, so the nesting areas lie within the NCS.
In comparison with Gharial, Mugger numbers were higher, 83 in 2015 and 66 in 2016, than those of Gharial, and the species was distributed throughout the survey section. Concentrations were highest in the midstream area in both years, where Gharial was also most evident in both years. Size class information for Mugger was not recorded, but incidental observation suggests that small sub-adults and juveniles (<2 m total length) were the most frequently encountered Muggers.
Human activities along the Parvati River consisted of net fishing, sand mining and water extraction. Fishing and agriculture activities were concentrated near the Chambal-Parvati confluence, diminished in the midstream survey section, then resumed in intensity upstream. In marked contrast to the main Chambal channel, sand mining was infrequent throughout the survey area; sand mining along the Chambal channel has intensified significantly in recent years and poses a major threat to mainstream nesting banks. Clearly, water extraction is the main resource removal activity on the Parvati at present, and occurred throughout the river course surveyed, even near the two sites where nesting occurred in 2017. Gharial presence during breeding and nesting in 2017 coincided in general with the absence of fishing activity, where sand mining was not detected, and where water extraction varied by site.
The Parvati River lies within the NCS where it reaches its confluence with the Chambal River, and a ~60 km stretch from the confluence upstream is protected. Previously, no records of Gharial using this stretch were available. The present study firmly establishes that this protected stretch of the Parvati River is an important additional segment of Gharial habitat within the NCS because Gharial utilizes this section for breeding, nesting, and hatchling habitats. Human activities are common along this stretch of river, particularly net fishing and water extraction, and pose potential threats to Gharial along the protected Parvati River section, as well as the continuing threats of these activities in the mainstream Chambal. Throughout its entire length inhabited by Gharial, from above Pali to the Yamuna confluence, and the adjacent protected areas upstream and downstream from that point on the Yamuna, these threats are combined in recent years with industrial level sand mining, particularly on the Madhya Pradesh and Rajasthan riversides, upstream.
During seasonally low water periods, the Parvati and the Kali Sindh Rivers are the primary sources of water for the mainstream Chambal. Three large storage dams (Gandhi Sagar, Jawahar Sagar, and Rana Pratap Sagar) and the Kota Barrage have severely limited water discharge into the mainstream Chambal, with zero water discharge at times during the lean season. Thus, in addition to its role as a major source of water for the Chambal, the Parvati River lower stretches provide suitable additional river habitats for Gharial.
In contrast, the other two rivers surveyed do not appear to be suitable Gharial habitat. On the Banas River, the Bisalpur Dam completed in 1999 has reduced the river to a few disjointed deep pools, and the river only flows during the monsoon when the dam gates are open. Occasionally, Gharial moves upriver during this time, only to be stranded once water levels recede. On the Kali Sindh River, the riversides are predominantly rocky, with few sandy areas. Lying outside the NCS boundary, the river has many anthropogenic disturbances in addition to the suboptimal riverside habitat and consequently harbours few Gharial beyond its confluence with the Chambal. An outlying record exists for the Kuno Wildlife Sanctuary in Madhya Pradesh for a single animal at a distance of 45 km from the confluence of the Kuno River in 2010.
Gharials prefer clean, fast flowing rivers with ample sand deposits, especially around sections with deep water. Recent studies have shown that Gharials undergo seasonal long distance travels, from feeding areas near major confluences during the monsoon, to their basking, breeding, and nesting areas upstream during the post-monsoon, winter, and pre-monsoon periods. Female Gharials prefer to nest in colonies on particular sandy stretches that provide high sand banks adjacent to deep water.
Although preferred areas tend to be consistent over decades, the exact location of colonial sites and the numbers of nests per site vary annually, depending on the local river topography produced during the previous monsoon. Traditional river activities by people tend not to deter Gharial from using nearby river habitats, but Gharial generally avoids areas subject to frequent disturbances, especially those where sand mining and net fishing are concentrated. Lateral connectivity in the river is essential because it allows Gharial to seasonally adjust their basking, breeding, and nesting activities to areas where disturbances are minimal.
Not only does our study highlight the importance of the upstream segments of the NCS, as suitable Gharial habitats and important water sources, but the Gharial counts of breeding adults and nests from the Parvati surveys add to the emerging picture of how many Gharial actually live in the Chambal River, largely within the confines of the NCS. In 2017, independent surveys by the Madhya Pradesh Forest Department and the Gharial Ecology Project, using different methodologies (boat counts vs. stationary counts, respectively), estimated that the mainstream Chambal River, from Pali upstream in Rajasthan to the Yamuna confluence (a river length distance of 415 km), contains a Gharial population >1250 individuals, with conservative counts of 617-761 mature adults (i.e. 65-121 males and 491-696 females).
In addition, above Pali to the Kota Barrage on the mainstream Chambal, 11 adults were tallied in the top 143 km of the NCS. We estimate an additional 10-15 mature adults inhabit the stretches of the Parvati and Banas in the areas surveyed in this study. Thus, the total population in the Chambal likely exceeds 1300 non-hatchling Gharial of all sizes, adding an additional 20+ mature adults to those already counted in the Chambal mainstream.
The fact that Mugger occurred in the lower Parvati that was surveyed may be indicative of the levels of disturbance noted. Some authors have speculated that there has been a gradual increase in Mugger numbers in the NCS, and have suggested that an apparent correlated trend for a decrease in Gharial abundance may be causative. Mugger-Gharial interactions are poorly understood presently and desire further study.
The NCS has well-documented issues regarding habitat degradation, in the form of sand mining, fishing, stone mining, riverside agriculture, and water extraction projects. Despite being administrated by three states, illegal sand mining, fishing and agriculture have shown few signs of subsiding, and sand mining especially has intensified in recent years to an industrial scale, with tractors and trolleys plying 24/7 almost year-round, during all but the 2-3 monsoon months when the river is in full mood. Backhoes are now common on riverbanks.
Recent considerations of river interlinking, particularly on the Parvati and Kali Sindh, need to take into account the devasting effects such projects would have on Gharial specifically, and on the water ow regimes upon which the Chambal fauna and flora depend. All of these anthropogenic activities threaten the entire ecosystem of the NCS, particularly the lateral connectivity of the river at present and the relatively unpolluted quality of the Chambal water.
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