Occurrence of the Siamese Crocodile (Crocodylus siamensis) in Kaeng Krachan National Park, Thailand

8 Pages·2002·0.36 MB·English

by  Platt, Steven G

NAT. HIST. BULL. SIAM Soc. 50(1): 7-14，2 002
OCCURRENCE OF THE SIAMESE CROCODILE
(CROCODYLUS SIAMENSIS) IN KAENG KRACHAN
NATIONAL PARK，T HAILAND
Steven G. Platf，An tony J. LynamZ，Yo sapong Temsiripon ，1g
and Manote Kampanakngarn4
ABSTRACT
Field surveys conducted during 2001 and 2002 confirmed the existence of Siamese croco-
diles (Crocodylus siamensis) along the Petchburi River in Kaeng Krachan National Park，
Thailand. An adult crocodile was photographed and回cks，drag marks，a nd other sign were
also found，su ggesting that as mall number of crocodiles occur within the park. This population
is threatened by illegal collecting and disturbance from commercial white-water tours. Addi-
tional surveys should be conducted to determine if crocodiles occur elsewhere in the Petchburi
and adjacent Pranburi watersheds. A conservation plan should be developed to ensure their
long-term viability.
Key words: Siamese crocodile，C rocodylus siamensis，c onservation，c 剖nera-trapping，Kaeng
Krachan National Park，τ'hailand.
INTRODUCTION
The Siamese crocodile (Crocodylus siamensis) formerly occurred in Thailand，
Cambodia，L aos，V ietnam，I ndonesia (Java and Kalimantan)，a nd Malaysia (Sabah and
Sarawak) (THORBJARNARSON，1 992; Ross，1 998). Populations throughout this r佃 gehave
dramatically declined as ar esult of habitat destruction，co llecting to stock crocodile farms，
and illegal hunting (Cox ETA L.，19 93; NAO，1 998; PLAπ&T RI，2 000; STUART & PLAπ，
2000)，an d C. siamensis is now regarded as one of the most endangered crocodilians in the
world (THORBJARNARSON，1 992; Ross，19 98). TheS iamese crocodile is considered Critically
Endangered “(facing an extremely high risk of extinction in the near future"; IUCN，1 994)
by the World Conservation Union (IUCN，20 00)，an d listed on Appendix Io f the Convention
on Intemational Trade in Endangered Species of Fauna and Flora (CITES).
IWildlife Conservation Society，P. O. Box 1620，P hnom Penh，C ambodia. Current addI官ss:Depar加entof Biology，
U凶versityof the Sou出，735 University A時間e，S開飢ee，Tenness民 37383-1000USA( Email: splatt225@加l.com)
2Wildlife Conservation Soα巴ty，P.O. Box 170，L ak払 Bangkok10210，T hailand (Email: 1Ivnam(iI)wcs.org)
3Crocodile Management Association of Thailand (CMAT)，P .O. Box 16，S riracha，C honburi 20110，百四land
(Email: XosaDong:(a)crocodileuniverse.cOI!l)
4National Parks Division，R oyal Forest D巴partment，Phaholyo白inRoad，B ang対len，Bangkok 10900，T hailand.
Received 1A ugust 2001; a∞epted 10 March 2002.
7
8 's百羽到G.PLArr ANroNYJ . L刊 AM，Yω，APONG百MSIRIPONG，MANσmKA岬刷雌NG組 N
Historically，C. siamensis w出 abundant泊 wetI組dsthroughout cen回1and southem
百叫組d(MoUsi凹，1864; BOCK，1 884; SMlTH， 1916; S班fH， 1919;S阻fH，1931). However，
酪 e紅Iy槌 1919declines had occurred泊 many釘目S槌 aresult of widespread shooting
(SMlTH， 1919; S町田， 1931)，組dby the late 1970's the only known wild population
∞>M
consisted of about 200 crocodiles ne BungBoraphet (GR BRIDGE，1 982). The
釘
population at Bung Boraphet w subsequentIyextirpated by illegal collecting to stock
錨
crocodile farms，d eliberate destruction of nests and eggs，組daccidental drOWI血gin fishing
nets伊E即日roN&K剖GSBURY，1962; Ross，1 998)，l eading Suvanakom & Youngprapakom
∞
(1987) to conclude the Siamese cro dilew回 ne釘泊gex曲lction泊百凶land.
Recent reports suggest白紙individualsor small populations of Siamese crocodiles still
persist in some protec低dare錨 ofThailand (Fig. 1). A single crocodile w邸 observed
d町ingas po出悼.ts町veyof Pang Si血 NationalPa此侭ATANAKO悶 EI'AL.，1 994)，佃 d
組 0，血erw:鎚 photogrョphedat Khao AngR u Nai Wildlife S釦 C卸値y侭REETlYUTANONT，
1993; B. Kekule，pe rsonal communication). Additionally，a c rocodile ca町田sw踊 found泊
Yot DomW ildlife Sanc伽創y，位ヨ.cksand合唱markswere observed in Phu Khieo Wildlife
Sanc伽ary，組dfield observations泊dica旬crocodilesmay occ町泊KaengKrachan National
Park依RE四 nπ'ANO附， 1993; GRAY EI' AL.，19 94). Weh ere report further evidence for
the occurrence of as mall population of Siamese crocodiles泊 KaengKrachan National
pk.
釘
STUDY AREA
Kaeng Krachan National Park (KKN町islocated泊由eTenasserim Mountains along
白e百国一Myanmarborder in Petchburi ∞and Prachuab Khiri Khan Provinces of southwestem
百回landσ'ig.1). Encompassing 291，5 ha，Ka eng Krachan is官lailand'slargest national
p釘k(DOBIAS，19 82).百letopography is characterized by steep mountain ridges with swift-
flowing rivers泊 res困ctedvalleys. lOtao Phanoen百lung(1，207 m) is the highest point畑
山ep釘k.τhesteep topogaphy and lack of roads make釦cessto much of the park difficult.
Semi-evergreen forest is the dominant vegetation with hill evergr nforest above 1，000 m
田
侭OUND，1985). Surrounding 1組也arel紅'gelydeforested，an d KKNPp ro総cts血ePetchburi
River watershed，wh ich supplies Kaeng Krachan Reservoir (DOBIAS，19 82).百lePetchburi
River is swift-flowing with numerous rapids.
OBSERVATIONS
Dur担.∞gal arge mammal s町veyof KKNP泊 J加uary2001 (Wildlife Conservation
Society，2 1)，o ne of us (A且，)found crocodile回，cksand命agmarks on as andb紅
(elevation c. 230 m) along血ePetchburi River (Fig. 2).官les組 db釘 W部 situated泊 awide
(c. 30 m) bend nin the river adjacent to ad 田P(2 to 3m ) pool with minimal current. Re紅ー
foot岡山(即 on the sandb紅 me部町吋 17.5cmf rom the posterlor 脚 抑of出eheel
to血etip of the longest claw. A Cam回kker@car即時岡，p(Cam回.ckSou血，Inc.，G eorgia，
USA) equipped with ap assive in企a∞r吋 motiondetector w鎚 placedat the site on 24
Ja直lUaryand recovered on 2M 創由2 1;as ingle photorecord of an adult crocodile w槌
obtained at 1435 hours on 1M arch部 itmoved across白，esandb紅 (Figure3). Using a
SIAMESE CROCODILE IN KAENG KRACI-IAN NATIONAL PARK 9
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Figure \. Map of Thailand showing sires where Siamese crocodiles have been reponed since 1990. I, Kaeng
Krachan National Park; 2, Pang Sida National Park; 3, Khao Ang Ru Nai Wildlife Sanctuary; 4, Yor
Dom Wildlife Sanctuary; and 5, Phu Khieo Wildlife Sanctuary.
regression equation developed to predict total length (TL) of American crocodiles
(Crocodylus acutus) from rear-foot track measurements (TL = 11.64RFT + 4.9; / = 0.87;
P < 0.001; PLATT & THORBJARNARSON, 2000), we estimated this crocodile to be
approximately 200 em long.
An additional survey was conducted from 4 to 7 April 2001 along 30 km of the
Petchburi River in KKNP, beginning at the base of Khao Phanoen Thung and ending at
Bong Leuk Ranger Station. Rapids and other navigational hazards precluclecl the use of
standard nocturnal spot! ight census techniques (BAYLISS, 1987); instead we searched
sandbars, exposed riverbanks, and other suitable substrates for crocodile tracks and drag
marks. Forefoot tracks, drag marks, and ventral scute impressions of a second crocodile
were found on 5 April approximately 5 km upstream from where the first crocodile was
camera-trapped. These tracks were on an exposed muclbank (elevation c. 245 m) along a
section of river with minimal cmrent. Measurable quality rear-foot tracks were not present,
and thus the total length of this crocodile could not be accurately estimated; however, drag
marks (25 to 30 em wide) suggest it was probably a subadult (TL :s; 180 em).
On 8 January 2002 a wildlife photographer reported encountering two crocodiles on
a sanely beach along the Petchburi River approximately 6.5 km upstream from K.U. Camp
(UTM 47P 1420618N 0533305E) in KKNP. AJL and YT visited the location on 2 February
JQ STEVEN G. PLAlT ANTO 'Y J. LYNAM, YOSAPONG TEMSIRIPONG, MANOTE KAMPANAKNGARN
Figure 2. Site where Siamese crocodile tracks were found in January 200 I and position of camera-trap on the
Petchburi River. Photo courtesy of Adam Oswell.
Figure 3. Siamese crocodile photographed at 1435 h on I March 2001 with a camera-trap set along the Petchburi
River in Kaeng Krachan National Park, Thailand. Total length estimated to be about 200 cm.
SIAMESE CROCODILE IN KAENG KRACHAN NATlONAL PARK 11
2002 and confinned the presence of at least one crocodile based on a1 7.5 cm long rear-
foot track found in moist sand at the rivers edge. On4 F ebruary 2002 AJL retumed to the
site where ac rocodile was photographed in 2001 (Fig. 3)，b ut found no evidence of the
animal. Given that track size at both locations was nearly identical，it is tempting to
speculate血atthese represent the same crocodile. If this is the case，t he crocodile had
moved upstream ad istance of at least 11.5 km.
DISCUSSION
Our findings and previous observations by Kreetiyutanont (1993) indicate that as mall
population of crocodiles，m ost likely C. siamensis，o ccurs within KKNP. The only other
freshwater crocodilian found in Thailand is the false gharial (Tomistoma schlegelii)
(THO悶 JARNARSON，1992); however，出isspecies is confined to ex回 mesouthem Thailand，
was last reported in 1970，an d is now believed extirpated from the coun町 (TAY LOR，1 970;
RATANAKORN ETA L.，1 994; SEBASTIAN，1 994). Furthennore，T. schlegelii is restricted to
heavily vegetated peat sw釘npsthroughout most of its range (SEBASTlAN，1 994; Ross，
1998; BEZUIJEN ETA L.，2 001)，a nd therefore unlikely to occur in the fast-flowing Petchburi
River. Nor does the crocodile we photographed appe tobe al ongirostrine species. We
紅
cannot rule out the possibility that the crocodiles in KKNP are escapees from crocodile
farms，po ssibly hybrids between C. siamensis and Saltwater crocodiles (Crocodylus porosus).
Thousands of crocodiles are held on farms in Thailand (LUXMOORE，1 992)，hy bridization
is widespread (SUVANAKORN & YOUNGPRAPAKORN，1 987)，a nd escapes，a lthough
in仕equentlyreported，h ave occurred (P. P. van D討k，personal communication). Future
efforts should therefore be made to ascertain the genetic identity of crocodiles in KKNP.
While we confinned the occurrence of only two individuals in KKNP，ot her crocodiles
probably escaped detection because spotlight surveys，th e most effective means of locating
crocodiles，p roved impractical and suitable tracking substrates along the river elimited.
紅
However，w e consider the viability of this population tenuous at best. Historically，t he
highest crocodile densities in Thailand probably occurred in floodplain swamps and lowland
rivers (SMITH，1 919; SMITH，1 931)，bu t recent reports indicate that the few remaining C.
siamensis are now confined to upland streams and rivers (KREETIYUTANONT，1 993;
RATANAKORN ETA L.，1 994; B. Kekule，p ersonal communication). RATANAKORN ETA L.，
(1994) consider such habitat m ginal，and speculate these easnever supported large
紅 紅
numbers of crocodiles. Interestingly，cr ocodiles are not listed in detailed faunal accounts
of血e釘eanow encompassed by KKNP( GAIRD阻 R，1915a and b; SMITH，19 15)，su ggesting
白eywere never common in the upper reaches of the Petchburi River. It is likely that
crocodiles from downstream areas closer human settlements immigrated to the upper
Petchburi River in response to chronic anthropogenic disturbance. Moreover，t he lower
reaches of the Petchburi River may now constitute ap opulation sink if monsoonal floods，
which occur during September and October，w ash hatchlings and juveniles downstream.
Regardless，g iven the critically endangered status of C. siamensis，t he population
within KKNP is of global conservation significance. Of particular concem is the threat
posed by the regional trade in living crocodiles to stock farms (THORBJARNARSON ETA L.，
2000a)，a s the loss of even af ew reproductive individuals from the KKNP population
could have disastrous demographic consequences. Although this population occurs within
12 STEVEN G. PLATT A肝 O附 J.LYNAM，Y OSAPONG TEMS困問NG，MANO百 KA問削A悶 G級 N
af ully protected national p紅k，the high price p泊dby crocodile farmers for breeding stock
provides as trong incentive for poaching (PLAIT ETA L.，u npublished). Fortunately，t he
limited accessibility of Petchburi River and the presence of downstream guard posts make
the illegal capωre and transport of living crocodiles ad ifficult proposition. Amending the
Wild Animal Reservations and Protection Act of 1992 to include protection for wild
crocodilians would provide additional safeguards against poaching and further enhance
recovery efforts.
Tourism represents another potential threat to crocodiles along the Petchburi River.
Commercial white-water rafting tours recently began between K.U. Camp and Bong Luek，
an area now known to harbor crocodiles. However，fo llowing the discovery of crocodiles
along this section of river，ra fting tours were suspended pending as tudy of the impacts on
crocodiles and other wildlife. These to swere conducted during the dry season，a p eriod
ぽ
coinciding with peak nesting activity in C. siamensis (PLAIT ETA L.，u npubl. data). Because
human disturbance may result in nest abandonment by attending female crocodi1ians (PLAI T，
1996)，w e recommend that the section of river between K. U. Camp and Bong Leuk remain
closed to tourists and be designated aS 町ictConservation Zone. Rafting tours should
henceforth be relocated to sections of the Petchburi River downstream企omBong Luek.
In addition，su rveys of other位ibutaries泊thepark should also be conducted to determine
if crocodiles exist elsewhere in the Petchburi and adjacent Pranburi watersheds da
，組
conservation plan developed to ensure the survival of血issmall population. Finally，o ur
experience further highlights the utility of camera-trapping as at ool for the study of rare
crocodilians (THORBJARNARSON ETA L.，2 000b).
ACKNOWLEDGMENTS
Field assistance was provided by Tongbai Charoendong，P rawing Kl加klay，Bruce
Kekule，J eηy Harmer，O rlando Guzman，A dam Oswell，M ark O'Shea，a nd the rangers of
Kaeng Krachan National Park. Thep hotograph in Figure 2w as provided by Adam Oswell.
百lesesurveys were supported by Wildlife Conservation Society，O utward Bound School
-Thailand，a nd“Save the Tiger Fund"，a j oint project of the National Fish and Wildlife
Foundation and ExxonMobile Co中oration.Dr. Plodprasop Suraswadi，Di rector-General of
the Royal Forest Department，is thanked for gr tingus permission to conduct fieldwork.
叩
Bruce Kekule is especially thanked for providing information on the current sta飢sof
crocodiles in Khao AngR u N氾WildlifeSanctuary. Stephen Johnson (WCS)，百lOmasR.
Rainwater，a nd Peter Paul van D討ksupplied critical references. Comments by百lomasR.
Rainwater，Tr avis Crabtree，Jo hn Thorbjarnarson，an d Peter Paul van D討kgreatly improved
this manuscript.
SIAMESE CROCODILE IN KAENG KRACHAN NATIONAL PARK 13
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