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Gharial ( Gavialis gangeticus ) populations and human influences onhabitat on the River Chambal, India SUYASH KATDARE a , ARJUN SRIVATHSA a , APOORVA JOSHI a , PRITISH PANKE a , RUCHIK PANDE a ,DHARMENDRA KHANDAL a and MARK EVERARD b, * a Tiger Watch, Sawai Madhopur, Rajasthan, India b Faculty of Applied Sciences, University of the West of England, Bristol, UK ABSTRACT1. The gharial, Gavialis gangeticus (Gmelin 1789), a piscivorous reptile of Asian river systems, is increasinglythreatened by diverse human pressures.2. Three survey expeditions were launched to monitor gharial populations, notable wildlife, and the activities andattitudes of local people in a 110km stretch of the Chambal River in the National Chambal Reserve (NCS), India.3. Only 15% of gharial observed in December 2009 were in the upstream 54% of the surveyed river length. Thiscoincides with the highest density of disturbance including water pumps, fi shermen, and the highest growth in fi shing activity since December 2008.4. Although fi shing is recognized as a signi fi cant threat to gharial, no strong relationship was found betweennumbers of gharial and fi shermen. However, numbers of water pumps, indicative of the intensity of agriculturalactivity, had a negative relationship with gharial numbers. This relationship was strengthened by omitting theupstream (Pali to Rameshwaram) survey reach, the tourist area of the NCS, which is also potentially affected byupstream reaches.5. The downstream 46% of surveyed river length in December 2009 supported 85% of gharial (consistent withtrends in other surveys), including 91.6% of males and 81.8% of juveniles. This reach is classi fi ed as a HighPopulation Recorded Area of high potential conservation importance, also containing better habitat quality andlower human disturbance.6. A positive relationship was found between gharial numbers and sand habitat features. However, the Davarto Ghoonsai survey reach had low gharial numbers despite abundant sand features, perhaps due to a substantiallength of the Ghoonsai sand bank having been converted or agriculture. This may have signi fi cant implications forgharial conservation.Copyright # 2011 John Wiley & Sons, Ltd.Received 21 September 2010; Revised 27 February 2011; Accepted 16 April 2011 KEY WORDS : Chambal River; gharial; mugger; survey; threats; fishing; agriculture; habitat loss INTRODUCTION The gharial, Gavialis gangeticus (Gmelin 1789), also knownas the fi sh ‐ eating crocodile, gavial, Indian gavial, Indiangharial or long ‐ nosed crocodile, is a large piscivorous reptileendemic to the Indian subcontinent naturally occurring inapproximately 20 000km 2 of riverine habitat in the Indus,Ganges, Mahanadi, Brahmaputra, and Irrawaddy river systems(Smith, 1939; Singh, 1978; Whitaker et al. , 1974; Groombridge,1987;Whitaker,1987;Hussain,1991,1999,2009).Gharialprefercalm and quiet areas of fast ‐ fl owing rivers. They are a long ‐ livedcrocodilianspecieswithagenerationlength(theageatwhich50%of total reproductive output is achieved) of 20years (Rao et al. ,1995). Reaching a length of up to 6m, gharial are also thesecond ‐ longest crocodilians after the saltwater or estuarinecrocodile ( Crocodylus porosus ) of Australasia.The common name ‘ gharial ’ derives from the Hindi word ‘ ghara ’ meaning pot or vessel, recognizing the resemblance toan inverted pot of the large protuberance at the tip of thesnouts of adult male gharial; gharial are the only crocodilesthat show sexual dimorphism. They are also accorded muchimportance in Indian mythology, including their depiction as *Correspondence to: Mark Everard, Faculty of Applied Sciences, University of the West of England, Coldharbour Lane, Frenchay Campus, BristolBS16 1QY, UK. E ‐ mail:
[email protected] # 2011 John Wiley & Sons, Ltd. AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS Aquatic Conserv: Mar. Freshw. Ecosyst. 21 : 364 – 371 (2011)Published online in Wiley Online Library(wileyonlinelibrary.com). DOI: 10.1002/aqc.1195 the holy ‘ vehicle ’ of the goddess Ganga. Gharial have slendersnouts armed with numerous sharp teeth that intersect to trap fi sh, which are the primary constituent of their diets. Theirmating season is during the months of November, Decemberand January. Sand banks, sand bars and sand islands play asigni fi cant role in the ecology of gharials as they are usedpreferentially as basking and nesting sites (Gharial Multi ‐ TaskForce, 2006). Throughout the summer months of March, Apriland May, female gharial clamber onto sand banks and islandsexposed by receding river levels to nest communally, a largenumber of females using the same sand bank to lay their eggs inthe sand (Rao and Singh, 1993). Parental care by the femalehas been observed for the fi rst few days after birth.Althoughasteadyrecoveryfromawidespreadearlierdeclineingharialpopulationswasreportedupto1997(Sharma,1999),therewas a subsequent 58% decline from 436 adult gharials to 182 in2006(Whitaker,2007).Itisbelievedthatthegharialisnowextinctin its former habitats in Myanmar and Bhutan, with a small butunknown number remaining in Pakistan as well as remnantpopulations in Nepal and the upper Brahmaputra in Bangladesh(Bustard,1980;Groombridge,1987;Ross,1998).Acrisissituationwas declared by the Indian government in January 2008 after amass death of around 111 gharial in the National ChambalSanctuary (the NCS, a wildlife sanctuary near Etawah in UttarPradesh, India) in 2007, the cause of which remains a matter of speculation but which is generally attributed to biomagni fi cationof heavy metals and other toxins in fi sh in the Yamuna River(reviewed by Gharial Conservation Alliance, 2008).The IUCN Red List (http://www.iucnredlist.org/apps/redlist/details/8966/0, accessed 27 February 2011) classi fi esgharialasCriticallyEndangeredonthebasisoflong ‐ termdeclineand the more recent, very rapid decline as well as low remnantwildglobalpopulationsoffewerthan250individuals.Thecausesof this decline include historic over ‐ hunting for skins, trophies,eggs,andindigenousmedicine,andmorerecentlytheconstructionof dams, barrages, irrigation canals, siltation, changes in rivercourses,arti fi cialembankments,sand ‐ mining,riparianagriculture,domestic and feral livestock, pollution and fi shing, which remainsamajorthreatasgillnetscontinuetorapidlykillgharialofallsizeseven in protected areas (Hussain, 1999, 2009).Between 1975 and 1982, India established 16 rehabilitationcentres for the captive breeding and release of gharial, and also fi ve gharial sanctuaries. The gharial population today is largelylimited to these fi ve refuges: the National Chambal Sanctuary(NCS); Katerniaghat Sanctuary; Chitawan National Park; theSon River Sanctuary; and the Satkosia Gorge Sanctuary. TheNCSisthelargest,foundedin1979andcovering425km 2 .Ittakesin approximately 400km of the Chambal River. The NCS isco ‐ administered jointly by the states of Uttar Pradesh, MadhyaPradesh and Rajasthan (Whitaker, 2007). The Chambal River isthe last stronghold for gharial, supporting 68% of the world ’ swild population.This paper reports on a series of three surveys of gharial andrelated biota and river uses and features along the ChambalRiver within the NCS. STUDY AREA The Chambal River is perennial, rising in the Vindhya Rangenear the Mhow district of Madhya Pradesh. It fl ows in apredominantly easterly direction, forming the boundary of thestates of Madhya Pradesh, Rajasthan, and Uttar Pradeshalong its course. Three major tributaries join the Chambal:the Parbati, Kali Sindh, and Banas rivers. A series of multipurpose dams (the Gandhi Sagar in Madhya Pradesh,and the Rana Pratap Sagar and Jawahar Sagar in Rajasthan)and a barrage (at Kota, Rajasthan) have been constructed inthe upper reaches of the river (Figure 1).The Chambal is reported to be one of the cleanest rivers inIndia, at least upstream of its con fl uence with the Yamuna,which carries substantial pollution from the greater Delhi area.Lined on either side by undulating ravines, the banks of theChambal River are diverse in habitat. Banks of sand, pebbles,boulders, bedrock, and deep ravines occur on both banks alongthe entire stretch of the river, frequently interspersed today bylarge areas of agricultural land. The most common agriculturalcrops in the sample area are Brassica juncea (mustard), Triticum vulgare (wheat), Cajunus cajan (yellow lentils), Pisumsativum (green peas) and Vigna radiata (green gram).The riverine ecosystem of the Chambal River supports agreat diversity of species of plants and animals, including, forexample, invertebrates such as various species of water skatersand diving beetles, seven species of turtle, and a wide variety of fi shspecies.Thelocalnamesofsome fi shfoundintheriver,withprobable taxonomic status determined from www. fi shbase.org(accessed 27 February 2011), are ‘ rohu ’ ( Labeo rohita ), bawas( Gibelioncatla ),baam( Mastacembelusarmatus ),dhegra(speciesuncertain), shingada ( Hemiarius sona ) and mahseer ( Tor species). Two species of crocodile are present: the gharial andthe mugger (the freshwater ‘ marsh crocodile ’ , Crocodylus palustris ). Some of the most endangered species in the world,including the Gangetic river dolphin ( Platanista gangetica gangetica ), smooth ‐ coated otter ( Lutrogale perspicillata ) andthe Indian skimmer ( Rhynchops albicollis ), are also found here.The ravines dominating much of both banks of the tightlymeandering river, interspersed with loose soil, rocky areas, andthorny vegetation, serve to channel monsoon fl ood water awayfrom villages nestled on higher ground. They are therebybene fi cial to village inhabitants as well as providing diversehabitat for wildlife. A variety of canids occur in these ravines,including the Indian wolf ( Canis indicus ), jackal ( Canis aureus ),Indian fox ( Vulpes bengalensis ), desert fox ( Vulpes vulpes pusilla ), and striped hyena ( Hyaena hyaena ). The sloth bear( Melursus ursinus ) is also known to occupy this diverseecosystem along with a range of other mammalian carnivores. OBJECTIVES OF THE GHARIAL SURVEY Following the mass death of gharial in 2007 in the ChambalRiver, three surveyexpeditionswere launched to monitor gharialpopulationsina110kmstretchoftheChambalRiverbetweenthevillagesofPaliandKhirkan(bothontheRajasthanbank).Othernotable wildlife and the activities and attitudes of local peoplewerealsorecorded.Allsurveystookplaceinthedryseasonwhenwater levels had receded and much of the river was visible.The three surveys took place in January 2008, December2008 and December 2009. The fi rst survey was a pilot, withthe second and third surveys intended to quantify threats anddetermine High Population Recorded Areas (HPRAs) forgharial within the overall river reach. The third surveyexpedition (December 2009) built on the methods and resultsof its predecessors, yielding the majority of the quantitative GHARIAL POPULATIONS AND HUMAN INFLUENCES ON THE RIVER CHAMBAL 365 Copyright # 2011 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 21 : 364 – 371 (2011) information reviewed in this study. However, informationfrom the third survey was compared with informationgathered in previous surveys enabling comparative accountsto be drawn from 3years of collected data, supporting otherconclusions in this study. The objectives of the series of surveys were to: • surveyacontiguousstretchofapproximately110kmalongthe Chambal River, downstream from Pali village toKhirkan village over 11days, dividing the entire sampleareainto 10segments based on the adjacent villages ontheRajasthan bank of the river; • record the number of gharial and mugger in each segment,andtodrawcomparisonswithdatafromearlierexpeditions.This enabled monitoring of increases, decreases, and shiftsin gharial numbers compared with previously recordedHPRAs which were de fi ned as reaches of river supportingthe strongest gharial populations; • quantify relationships with direct threats such as fi shingand sand/stone mining, and also indirect threats suchas agriculture and the fl attening of ravines to createagricultural land; • assess the habitat and land ‐ use patterns along the banksof the river to estimate the extent of natural habitatdestruction; • document aspects related to the socio ‐ economic status of the people around villages adjacent to the river, andexamine the attitude of villagers towards gharial along theRajasthan bank of the river; • study fl oral diversity; and • record sightings and locations of other threatened faunafound along the river. METHODS Each selected segment was surveyed over a 1 ‐ day period, theentire survey stretch taking over 11days to complete. Thetiming of sampling was during good daylight between 10:00hrsand 17:00hrs. The fi rst segment of the stretch from Pali toRameshwaram (approximately 20km lying within the tourismzone of the sanctuary) was surveyed by motorboat owing tobank ‐ side sampling dif fi culties. The remaining 10 segmentsfrom Rameshwaram to Khirkan were surveyed on foot withthe survey team walking along the river bank. Walking surveyswere supported by porters, a cook, and camel cart enabling thesurvey team to camp and obtain meals on the river bank.Data captured included observed gharial and muggernumbers, quanti fi cation of threats, assessment of land ‐ usepatterns along the banks, and records of fl ora and otherthreatened fauna in the area. Visual observations of gharial,muggers, other fauna, and human activities in the river or on thebanks were aided by Olympus 10×50 fi eld binoculars. TwoGarmin e Trex GPS units were used to record the coordinates of the spot perpendicular to gharial and mugger locations at everysighting. The speci fi c location of gharial and muggers wasnoted, classifying them by position including ‘ in water ’ , ‘ on sandbank/bar/island ’ , ‘ on rocks ’ or ‘ on mud banks ’ . The sex of observedgharialwas alsorecordedintheDecember 2009survey,classifying them as ‘ males ’ based on a clear protuberance at thetip of the snout, sub ‐ adults/females for large individuals lackingsuch a protuberance, and juveniles for smaller specimens.It is accepted that there are more accurate methods forquantifying the number of mature gharial, including, forexample, the recommendation by Hussain (1999) to use gharialnest counts as they are easily visible and can be counted atwell ‐ known locations many of which have been monitored fordecades. However, part of the purpose of this survey was todetermine the impacts of disturbance, much of which appear tohave occurred on these historic breeding habitats. Other datacapturemethodscontributingtouncertaintiesincludevariationsin survey stretch lengths and also the use of the motorboatbetween Pali and Rameshwaram. Gharial may also tend to hidewhere disturbance is more frequent, potentially affecting their fi tness. However, the selected methods were largely enforced by Kota BarragePaliEtawah R. Yamuna R. Parbati Javahar Sagar DamRana Pratao Sagar DamGandhi Sagar Dam Figure 1. Map of the National Chambal Sanctuary (NCS). S. KATDARE ET AL. 366 Copyright # 2011 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 21 : 364 – 371 (2011) limitationsofaccessandthesurveybudget,andservetoprovidean indication of principal trends and associations.GPS co ‐ ordinates were also taken at every signi fi cantchange in habitat or land use along the bank. In all, 99 pointswere identi fi ed along the surveyed stretch of river, marked withGPS coordinates, assessed for habitat and land use, and scoredfor the presence/absence of human disturbance. A location wasconsidered ‘ disturbed ’ when one or more of the following wasobserved: human activity, cattle activity, fi shing activity, waterpumps, sand/stone mining, fl attened ravines, and agriculture.Fishing, the presence of water pumps, and sand/stone miningwere recorded and quanti fi ed as direct threats. All the datacollected were entered on pre ‐ prepared data sheets in the fi eld. RESULTS Data gathered from survey reaches are summarized in Figure 2and Table 1. A total of 122 gharial were counted in the 110kmstretch between Pali and Khirkan in the third (December 2009)survey, comprising 11 males, 22 juveniles and 89 sub ‐ adults/females. The stretch between Kemkutch and Khirkan wasexclusive to the 2009 survey, lacking comparative data fromprevious surveys. Relatively low populations of gharial weredocumented in the December 2009 survey between the villagesofPaliandGohta(the fi veupstreamsurveyreaches),collectivelycomprising 15% of the total observed gharial population over54% of the total river length surveyed. This length of rivercoincides with the highest density of water pumps, the mostobserved fi shermen, and the highest growth in numbers of fi shermen between December 2008 and 2009.Fishing presents a direct threat to the survival of gharial(Hussain, 1999). However, no strong relationship was observedbetween numbers of gharial and fi shermen (R 2 =0.017 onFigure 3) in December 2009. Furthermore, a regression of changes in observed gharial numbers and numbers of fi shermenacross the Pali to Kemkutch sites between December 2008 and2009 surveys reveals no association (R 2 =2E ‐ 06).Thenumber ofwater pumpswithin eachsurveysegment wastaken to indicate the intensity of agricultural activity. InDecember 2009, 128 water pumps were counted from bothbanksacrossthewhole110kmreachandanegativerelationshipwas found between the numbers of water pumps and gharial(R 2 =0.086 on Figure 3). Data for the upstream site (Pali toRameshwaram) has a signi fi cant effect on the relationship of water pumps to gharial numbers in Figure 3 as, when it isremoved from the regression, the R 2 value for this negativerelationship rises from 0.086 to 0.1728, suggesting thatotherfactorsmaybein fl uencingthe densityofobservedgharial.This may include, for example, the Pali to Rameshwaram No. MuggerJan 08 Dec 08 Dec 09 10 5 16 JharelKhrkanRameshwaramShankarpuraBhagodaBilwasaGohtaDawarGhoonsaiKasedKemkutchPali HPRA 25 11 30 2 17 4 13 6 10 3 3 11 6 13 8 8 7 7 5 7 1 9 5 11 2 0 2 0 0 0 10 21 3 9 10 17 1 6 7 40 69 53 10 13 21 1 2 0 6 4 9 -- 10 No. GharialJan 08 Dec 08 Dec 09 - - 5 No. Fishermen Dec 08 Dec 09 7 6 5 2 3 10 9 13 4 5 6 6 8 10 4 17 1 17 - 11 No. Water pumps Dec 08 Dec 09 5 5 75 71 9 9 4 11 9 3 1 5 1 4 7 8 10 12 - 0 Stretch lengthin km821.5198108.285.65.59.6 Figure 2. Length, disturbance, mugger and gharial numbers recorded in survey stretches.Table 1. Gharial numbers recorded in survey segments during December 2009, divided into males, sub ‐ adults/females and juveniles together with theiruse of habitatVillage stretch Males Sub ‐ adults/FemalesJuv. No. in water No. on Sandbank/bar/islandNo. on rocks No. onmud banksTotalPali ‐ Rameshwaram ‐ 2 ‐ ‐ ‐ ‐ 2 2Rameshwaram ‐ Shankarpura ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Shankarpura ‐ Baghoda ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Baghoda ‐ Bilvasa 1 6 2 6 ‐ 3 ‐ 9Bilvasa ‐ Gohta ‐ 5 2 2 ‐ 5 ‐ 7Gohta ‐ Davar 3 50 ‐ 42 7 ‐ 4 53Davar ‐ Ghoonsai ‐ 3 ‐ 2 1 ‐ ‐ 3Ghoonsai ‐ Kased 2 10 5 15 2 ‐ ‐ 17Kased ‐ Kemkutch 5 9 7 9 12 ‐ ‐ 21Kemkutch ‐ Khirkan 1 3 6 3 7 ‐ ‐ 10 GHARIAL POPULATIONS AND HUMAN INFLUENCES ON THE RIVER CHAMBAL 367 Copyright # 2011 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 21 : 364 – 371 (2011) survey stretch being the longest (21.5km compared with a meanof 9.8km for the remaining survey stretches downstream toKhirkan), it being the location of the tourist area, and alsopotential impacts from the upstream unsurveyed reaches of theChambalRiverandatributary.Itisalsonotablethatthehighestincidence of water pumps in the December 2008 and December2009 surveys did not coincide with the highest density of fi shermen, and that there wasalso a signi fi cant growthin fi shingactivity(totalsof47and86)andaslightincreaseinwaterpumps(a total of 121 rising to 128) between the December 2008 andDecember 2009 surveys, emphasizing the diversity and growthof pressures throughout the NCS.High Population Recorded Areas (HPRAs) in 2009 wereidenti fi edbetweenthevillagesofGohtaandKhirkan,supporting85% of the total recorded number of gharial. This trend wasconsistent with data from January 2008 and December 2008(though these surveys did not take in the downstream Kemkutchto Khirkan reach). These HPRAs are of high importance sincethey are likely to signify better habitat quality and lowerdisturbance(particularlylowernumbersofrecordedwaterpumpsand fi shermen although fi shing activity was generally increasingbetween December 2008 and December 2009). They maytherefore be priorities for long ‐ term protection.These contiguous HPRAs supported 91.6% of the total malepopulation in the sample area in December 2009, suggestingstrong viability for substantial long ‐ term breeding within thegharial population. The same stretch also constituted 81.8% of the total juvenile population, indicating suitable growingconditions and better habitat suitability.Analysis of the points marked with GPS and assessed forthe presence/absence of human disturbance, habitat, and landuse in the December 2009 survey revealed that 79.8% of riverlength was subject to human disturbance (cattle activity, fi shingactivity, water pumps, sand/stone mining, fl attened ravines,and/or agriculture). Sand banks/bars/islands, important forgharial nesting and basking, were found to be present in 32.3%of total river length. Gharial numbers were positively related tothe percentage of these features observed within surveystretches (R 2 =0.013). However, the Davar to Ghoonsai surveyreach was perceived as of speci fi c signi fi cance as gharialnumbers were low despite abundant sand features (3% and31%, respectively), while the downstream Ghoonsai to Kasedreach had relatively high gharial numbers despite lacking sandfeatures (17% and 0%, respectively). Removing the Davar toGhoonsai reach from the regression strengthens the positivecorrelation of gharial numbers with percentage of sand features(R 2 =0.1676) while removing the Ghoonsai to Kased reach aswell strengthens it further (R 2 =0.2389). This is believed to bedue to a substantial length of the Ghoonsai sand bank nowhaving been converted into agricultural land (i.e. subject tosubstantial disturbance); a subsequent decline in numbers of the long ‐ lived gharial may be anticipated in response tochanges to this important breeding habitat.Figure3alsoplotsaregressionbetweennumbersofobservedgharial and mugger at the survey sites in December 2009. Nostrong relationship was observed (R 2 =0.0034). However,removal of the Pali to Rameshwaram survey stretch from thisregression identi fi esa weakly positive relationship (R 2 =0.0692)suggesting differences in response to habitat and disturbance,including potential in fl uences from the unsurveyed upstreamreach of the Chambal River and its tributary. DISCUSSION Although a substantial breeding population remains within thelimitsoftheNCS,uncontrolledhumanpressurescontinuetoposeathreattothesurvivalofitsgharialpopulation.Ofthetotalriverlength sampled, 79.8% faced disturbance owing to direct orindirect human activity. With increasing fi shing activity in theriver channel and agricultural activities along its banks, the laststronghold of the gharial remains perilous. We review theimplications of various of these pressures ongharial populations. Fishing Illegal fi shing in the sanctuary has been identi fi ed as the mostsigni fi cant and direct threat to the gharial, with cast netswidespreadacrosstheriverwidthresponsibleforentanglingand 00 10 20 30 40 50 601020304050607080 N u m b e r o f m u g g e r s , f i s h e r m e n o r W a t e r p u m p s MuggersWater pumpsFishermenLinear (Muggers)Linear (Water pumps)Linear (Fishermen) Number of gharial -10 Figure 3. Relationships between number of muggers, fishermen and water pumps and numbers of gharial by survey stretch in theDecember 2009 survey. S. KATDARE ET AL. 368 Copyright # 2011 John Wiley & Sons, Ltd. Aquatic Conserv: Mar. Freshw. Ecosyst. 21 : 364 – 371 (2011)
