Status, distribution and conservation of crocodiles in Sri Lanka

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  • Status, distribution and conservation of crocodiles in Sri Lanka

    Charles Santiapillai *, Mangala de Silva

    Department of Zoology, University of Peradeniya, Sri Lanka

    Received 20 January 1999; received in revised form 7 July 2000; accepted 25 July 2000

    Abstract

    Two species of crocodile occur in Sri Lanka, namely the marsh crocodile (Crocodylus palustris) and the estuarine crocodile(Crocodylus porosus), confined largely to the low-country in the first peneplain. Both species have declined in range and numbersince the turn of the century, mainly through over-hunting for hide and meat in the past, and conversion of their habitat to other

    land-uses by man at present. They have been completely extirpated from the Jana peninsula in the north. The study on the statusand distribution of crocodiles was carried out from 1991 to 1996 during which crocodiles were recorded from 113 localities, 105 ofwhich were inhabited by the marsh crocodile (C. palustris), while 33 localities harboured the estuarine crocodile (C. porosus). The

    two species were sympatric in 25 localities. Of the 105 localities from which C. palustris were recorded, it was considered rare in 62,common in 35, abundant in five, and perhaps extinct recently in three. Of the 41 large river systems, 32 were found to supportcrocodiles. Both species of crocodile are particularly abundant and secure in the countrys two premier conservation areas: the

    Ruhuna National Park in the south-east and the Wilpattu National Park in the north-west. It is estimated that there could be atleast 1220 marsh crocodiles, and perhaps no more than 300 estuarine crocodiles in Sri Lanka. Crocodiles are being threatened byindiscriminate destruction of the islands mangroves and marsh vegetation for human habitation and prawn farming. In Sri Lanka,the marsh crocodile is known to tolerate concentrations of salt higher than that in sea water for a long time. The estuarine crocodile

    is known to move a considerable distance in land from the coast. The strong territorial behaviour among the male estuarine cro-codiles may perhaps help space the individuals. Crocodiles have a poor image in Sri Lanka. Most rural people consider them aserious and potentially dangerous pest and so do not regret their disappearance from their neighbourhood. Marsh crocodiles can be

    ranched, but the concept of sustainable utilization of wildlife in general is still anathema to a large segment of the population in SriLanka. On the other hand, if crocodiles could benefit people, they are not likely to become extinct.# 2000 Elsevier Science Ltd. Allrights reserved.

    Keywords: Marsh crocodile Crocodylus palustris; Estuarine crocodile C. porosus; Poaching; Ranching; Conservation; Sri Lanka

    1. Introduction

    The family Crocodylidae is represented by 23 species(King and Burke, 1989), of which two are found in SriLanka, Crocodylus palustris, the freshwater (freshy),marsh, mugger, or swamp crocodile, and C. porosus, thesaltwater (salty) or estuarine crocodile. Both are listedin Appendix I of CITES (Convention on InternationalTrade in Endangered Species of Wild Fauna and Flora).According to the current IUCN listing given by Baillieand Groombridge (1996), C. palustris is classified asvulnerable but C. porosus is no longer consideredthreatened and so may be included in the lower

    risk category. However, within Sri Lanka, both C.porosus and C. palustris would meet the IUCN criteriafor being critically endangered and endangeredrespectively. Although the two species have been pro-tected legally in Sri Lanka under the Fauna and FloraProtection Ordinance of 1938, they can still be huntedon a special licence (Klemm and Navid, 1989). Identifi-cation with unaided eye at a distance or when the twospecies are in water is often dicult. When lying on theground, the estuarine crocodile, being more solitary,seldom basks in groups unlike the marsh crocodile(Whitaker and Whitaker, 1977). However, in Sri Lankait has been observed basking with marsh crocodiles.Dierences in the structure, habitat preferences, andbreeding of the two species of crocodile in Sri Lanka aregiven in Table 1.

    0006-3207/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.PI I : S0006-3207(00 )00126-9

    Biological Conservation 97 (2001) 305318

    www.elsevier.com/locate/biocon

    * Corresponding author. Tel.: +94-8-224-784; fax: +94-8-232-343.

    E-mail address: csanti@slt.ik (C. Santiapillai).

  • In Sri Lanka, the number and geographical range ofcrocodiles in general, and of the marsh crocodile inparticular, seem to have been aected by the growthand spread of the human population. As there are nonatural lakes in Sri Lanka, the construction of thousandsof irrigation reservoirs or tanks by the ancient kings inthe low country Dry Zone, greatly enhanced the spreadand survival of the marsh crocodile. At the same time,given the inherent economic value of their skins, croco-diles were also subjected to illegal hunting. As a keystonespecies, crocodiles are said to help maintain ecosystemstructure and function through predation on fish, recy-cling of nutrients, and maintenance of water refugiaduring droughts (King, 1988). Most people living in therural areas in Sri Lanka regard crocodiles as dangerousanimals, and would gladly have them removed fromtheir neighbourhood or killed, even though judgingfrom press reports, incidences of crocodiles killing peopleor domestic animals today are not common as they werein the past. According to Whitaker and Whitaker(1977), in Sri Lanka more people are killed by bualoesand cows than crocodiles. According to Groombridge(1982), crocodiles are threatened throughout their rangeprimarily by illegal hunting for their hide and meat, andto a lesser extent by habitat destruction. If this is so,once illegal hunting is eliminated, crocodile populationsshould be able to recover, provided their habitats arenot destroyed (Webb and Manolis, 1989). This isborne out by the fact that although many crocodilepopulations have declined in range and size, no speciesof crocodile has yet been driven to extinction. Be that asit may, in Sri Lanka conversion of habitat in generaland the draining of the wetlands in particular seem to

    undermine seriously the long-term survival of croco-diles.Crocodiles have been poorly studied in Sri Lanka

    since Deraniyagalas (1953) pioneering work, and thesurvey carried out by Whitaker and Whitaker (1977,1979). No scientific research had been carried out oncrocodiles, until the preliminary study by Santiapillai etal. (2000) in the Ruhuna National Park from 1991 to1994. More recently, Porej (1997) identified and asses-sed the status of crocodiles from 20 wetland sites in SriLanka. Whitaker and Whitaker (1979) recommendedfurther, detailed survey to map the exact distributionand status of the crocodiles in Sri Lanka, and followingtheir suggestion, this paper re-examines as much aspossible, the distribution and status of the two species.

    2. Methods

    The study on the distribution and status of crocodilesin Sri Lanka was carried out from 1991 to 1996, andwas based on (i) already published information, (ii)direct evidence from surveys of water-holes and rivers,in the so called safe areas of the island, (iii) indirectevidence obtained from interviewing refugees from theunsafe areas, and (iv) results of a workshop on cro-codile conservation and management that the authorsconducted for the rangers of the Department of WildlifeConservation in 1993. Our own ecological study of thecrocodiles was carried out in the Ruhuna National Parkbetween 1991 and 1994 (Santiapillai et al., 2000), whereall observations on the crocodiles were made from avehicle, using 742 binoculars, from 0600 to 1900

    Table 1

    Characteristics of Sri Lankas crocodiles species

    Marsh crocodile (C. palustris) Estuarine crocodile (C. porosus)

    Skull Broad-snouted Snout not so broad

    Post-occipital scutes Present Vestigial or absent

    Skin Olive-green Brassy yellow

    Osteoderms Rectangular Ellipsoid

    Maximum size

    Males 4.0 m 6.4 m

    Females 3.0 m 5.5 m

    Size at maturity

    Males 2.7 m 2.7 m

    Females 1.6 m 1.7 m

    Habitat Rivers, marshes and irrigation reservoirs River estuaries and coastal lagoons

    Breeding

    Mating November April

    Nesting FebruaryMarch JuneAugust

    Hatching MayJune SeptemberOctober

    Nest type Hole Mound

    Clutch size 1030 2070

    Hatchling size 2025 cm 2530 cm

    Temperament Aggressive Very aggressive

    306 C. Santiapillai, M. de Silva / Biological Conservation 97 (2001) 305318

  • hours, during which time, most water holes in the parkwere visited. At every sighting of crocodiles, their number,location, habitat and behaviour were noted. Wheneverpossible, the species was identified based on field criteriasuch as the shape of the dorsal osteoderms (Table 1).This is often dicult, as Daniel (1983) pointed out, thetwo species are dicult to distinguish in the field, espe-cially smaller individuals. Wherever possible, the lengthof the animals was estimated visually. Four categorieswere recognized: hatchlings (2 m). It wasnot possible to determine the sex of the individuals inthe field. Marsh crocodiles were assigned to the follow-ing categories based on their number: (i) rare (30 animals), and (iv) probably extinct (when therewere no recent records, but crocodiles were known tohave occurred in the past). Estuarine crocodiles weremuch rarer wherever they occurred, except at the salineKokkarai villu in the Wilpattu National Park.

    3. Results and discussion

    Crocodiles have been reported from 113 localities(Table 2), two of which are the Wilpattu National Park(WNP) in the north-west and the Yala Protected-AreaComplex (YPC) in the south-east. All the localities aredrained by rivers (Fig. 1). Crocodiles were found to berare in 67 (59.3%), common in 37 (33%), abundant in 5(4.5%), and probably extinct in 4 (3.6%). Of the 111localities (excluding the WNP and YPC), C. palustriswas recorded from 100, C. porosus from 31 (Fig. 2), andthe species coexisted in 20 (Table 3). Of the 103 riverbasins found in Sri Lanka, C. palustris occurred in 45,and C. porosus in 27. Of the 41 large river systems wherethe discharge of water into the sea exceeds 100 millionm3/year, crocodiles were recorded from 32. Theremaining 9 river systems (Table 4) represent eitherareas from where there has been no recent informationon crocodiles, or areas that could not be visited forsecurity reasons. In both WNP and YPC, crocodilesoccur in almost all water holes. Fig. 2 shows the presentdistribution of the two species.The location no. 1 of the single specimen of C. palus-

    tris (Table 2) is a canal in the southern part of the city ofColombo. This crocodile had apparently come from thereservoir and stream to the east of the city in the presentcapital of Sri Jayewardenepura or Kotte. This city wasthe capital of Sri Lanka during the Portuguese andDutch colonial periods too, at which time, the streamand the lake were modified into a moat to protect thecity. Crocodiles were kept in the moat, and a few des-cendants still remain. This area does not lie in anymajor river basin.

    Whitaker and Whitaker (1979) recorded crocodilesfrom 32 river systems, and Porej (1997) found them in16 river systems (Table 5). The former researchersrecordedC. palustris from 12 river systems, andC. porosusfrom 17 river systems, and Porej (1997) recorded thetwo species from 9 and 10 river systems, respectively.These findings agree with the present data except that,in our study, crocodiles were not recorded from six riverbasins (nos 3, 10, 14, 37, 65 and 97) in three of which Whi-taker and Whitaker (1977) had recorded their presence. C.porosus was recorded by them from the estuaries of (no.3) Kalu ganga, (no. 10) Koggala oya, and (no. 97)Kalagamu oya. While it is possible that individuals ofthis species may still occur in the estuaries of Kaluganga and Kalagamu oya, the species is already extinctin Koggala oya.

    3.1. Range, distribution and habitat of crocodiles

    3.1.1. Marsh crocodileThe historical range of the marsh crocodile extended

    from Iran in the west to Bangladesh in the east, and thepresent geographic distribution extends throughout theIndian subcontinent from Baluchistan in the west toAssam in the east, and from Nepal in the north to SriLanka in the south. It has also been recorded from Iranand Myanmar (Daniel, 1983). However, within thisrange, the species has become locally extinct over largeareas, and today viable populations occur mostly withinprotected areas. According to Whitaker and Whitaker(1989), in Iran, Pakistan, Nepal and Bangladesh, thereare very few crocodiles left; their long-term survivalprospects outside the protected areas appear grim.In Sri Lanka, prior to the large-scale conversion of

    forests and the expansion of the human population, themarsh crocodile was widely distributed across much ofthe low-country Dry Zone. According to Clark (1901),all the tanks, rivers and forest pools swarm withthem. Tennent (1859) referred to the still waters andtanks of the northern provinces literally teeming withcrocodiles. The marsh crocodile was once common evenin the Jana peninsula (Ferguson, 1877) where it nolonger occurs. Today its range is almost confined to thefirst peneplain in the low country, below an altitude of100 m, where it is still widely distributed and is particu-larly common in large irrigation tanks built by the ancientkings (Table 2). The highest elevation from which themarsh crocodile has been recorded in Sri Lanka in recenttimes is 230 m a.s.l, in Randenigala reservoir built acrossthe Mahaweli river, at a distance of about 160 km fromthe delta. In India, it has been recorded from an altitudeof 420 m in the Corbett National Park (Whitaker andWhitaker, 1984).The distribution of the marsh crocodile in Sri Lanka is

    still extensive (Fig. 2). It is interesting to note that in allthe river systems where C. porosus occurs, C. palustris is

    C. Santiapillai, M. de Silva / Biological Conservation 97 (2001) 305318 307

  • Table 2

    Recent records of crocodiles in Sri Lankaa

    No. Location Categoryc Reserved C. palustrise C. porosuse Statusb River basinf NRBb

    1 Wellawatta Canal C + R (minor basin)

    2 Bellanwila-Attidiya Marsh M SA + C Bolgoda Lake 2

    3 Bolgoda Lake E + X Bolgoda Lake 2

    4 Panadura Ganga E/R + X Bolgoda Lake 2

    5 Anguruwathota Ganga R + R Kalu Ganga 3

    6 Athruwela Wewa T + + C Benthara Ganga 4

    7 Bentota River E/R + + R Benthara Ganga 4

    8 Dedduwa Wewa T + + R Benthara Ganga 4

    9 Indigaha Thotupola R + + C Benthara Ganga 4

    10 Indirilla Ganga R + + X Benthara Ganga 4

    11 Kaluwamodera Ganga E + R Madu Ganga 5

    12 Madu Ganga E + + R Madu Ganga 5

    13 Madampe Oya E + + R Madampe Oya 6

    14 Molapu Oya E SA + + R Molapu Oya 7

    15 Gin Ganga E + + R Gin Ganga 9

    16 Koggala Estuary E + X Koggala Ganga 10

    17 Nilwala Ganga E/R + + R Nilwala Ganga 12

    18 Rekawa Lagoon L + R Rekawa Oya 15

    19 Muruthawela Wewa T + + C Urubokke Oya 16

    20 Buruthagolla Wewa T NP + C Walawe Ganga 18

    21 Uda Walawe Wewa T NP + R Walawe Ganga 18

    22 Chandrika Wewa T + R Walawe Ganga 18

    23 Ridiyagama Wewa T + R Walawe Ganga 18

    24...

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