The Siamese crocodile (''Crocodylus siamensis'') is a medium-sized freshwater
crocodile native to
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
(
Borneo
Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...
and possibly
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mos ...
),
Brunei
Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by t ...
,
East Malaysia
East Malaysia (), or the Borneo States, also known as Malaysian Borneo, is the part of Malaysia on and near the island of Borneo, the world's third-largest island. Near the coast of Sabah is a small archipelago called Labuan. East Malaysia li ...
,
Laos,
Cambodia
Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailan ...
,
Myanmar
Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
,
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
and
Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
. The species is
critically endangered and already
extirpated
Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...
from many regions. Its other common names include Siamese freshwater crocodile, Singapore small-grain, and soft-belly.
Phylogeny
![Crocodylus ossifragus-Naturalis-PeterMaas2](https://upload.wikimedia.org/wikipedia/commons/7/72/Crocodylus_ossifragus-Naturalis-PeterMaas2.jpg)
Below is a
cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
based on a 2018
tip dating Tip dating is a technique used in molecular dating that allows the inference of time-calibrated phylogenetic trees. Its defining feature is that it uses the ages of the samples to provide time information for the analysis, in contrast with traditio ...
study by Lee & Yates simultaneously using
morphological, molecular (
DNA sequencing), and
stratigraphic
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithostra ...
(
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
age) data,
as revised by the 2021 Hekkala ''et al.''
paleogenomics Paleogenomics is a field of science based on the reconstruction and analysis of genomic information in extinct species. Improved methods for the extraction of ancient DNA (aDNA) from museum artifacts, ice cores, archeological or paleontological site ...
study using DNA extracted from the extinct ''
Voay''.
Characteristics
![Siamese Crocodile-Biblical Zoo](https://upload.wikimedia.org/wikipedia/commons/2/2f/Siamese_Crocodile-Biblical_Zoo.JPG)
The Siamese crocodile is a medium-sized, freshwater
crocodilian, with a relatively broad, smooth snout and an elevated, bony crest behind each eye. Overall, it is olive-green, with some variation to dark-green.
Young individuals measure and weigh , growing to a length of and a weight of as an adult. Three individuals ranging from in total length and weighing from had bite force of . Large male individuals reach and in weight.
Distribution and habitat
Siamese crocodiles occur in a wide range of freshwater habitats, including slow-moving
river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...
s and
streams,
lake
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...
s, seasonal
oxbow lakes
An oxbow lake is a U-shaped lake or pool that forms when a wide meander of a river is cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called '' resacas''. In Australia, oxbow lakes are calle ...
,
marsh
A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found a ...
es and
swampland
A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s.
Behaviour and ecology
Despite conservation concerns, many aspects of ''C. siamensis'' life history in the wild remain unknown, particularly regarding its reproductive biology.
Adults feed mainly on
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
and
snakes, but also eat
amphibians and small
mammals
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...
.
Very little is known about the
natural history of this species in the wild, but females build mound-nests constructed from scraped-up plant debris mixed with mud.
In captivity, these crocodiles breed during the wet season (April to May), laying between 15 and 50 eggs, which are then guarded until they hatch.
After
incubation, the female will assist her young as they break out of their eggs and then carry the hatchlings to the water in her jaws.
Pure, unhybridised examples of this species are generally unaggressive towards humans, and there are only four confirmed attacks, none of them fatal. One was defending its young, another was probably defending itself, one was provoked, and the reason for the last is unclear. A fifth attack in 1928 that was probably done by a Siamese crocodile was fatal, with the victim being a child.
Threats
Siamese crocodiles are under threat from human disturbance and habitat occupation, which is forcing remaining populations to the edges of their former range.
Extinct from 99% of its original range, the Siamese crocodile is considered one of the least studied and most critically endangered crocodilians in the world.
Although few wild populations remain, more than 700,000 ''C. Siamese'' are held on commercial
crocodile farms
Crocodiles (family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant memb ...
in Southeast Asia.
In 1992, it was believed to be extremely close to or fully
extinct in the wild until 2000 when scientists from
Fauna and Flora International and the Government of Cambodia's Forestry Administration confirmed the presence of Siamese crocodiles in the
Cardamom Mountains
The Cardamom Mountains ( km, ជួរភ្នំក្រវាញ, ; th, ทิวเขาบรรทัด, ), or the Krâvanh Mountains, is a mountain range in the south west of Cambodia and Eastern Thailand. The majority of the range ...
in Southwest Cambodia. Since then, surveys have identified around 30 sites in Cambodia that contain wild Siamese crocodiles (conservatively estimated to number between 200 and 400 individuals in total), a tiny population in Thailand (possibly as few as two individuals, discounting recent
reintroductions), a small population in Vietnam (possibly fewer than 100 individuals), Cat Tien National Park has about 200, and a more sizeable population in
Laos. In March 2005, conservationists found a nest containing juvenile Siamese crocodiles in the southern Lao province of
Savannakhet. There are no recent records from
Malaysia
Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
,
Burma
Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
or
Brunei
Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by t ...
. A small but important population of the crocodiles is also known to live in
East Kalimantan
East Kalimantan ( Indonesian: ) is a province of Indonesia. Its territory comprises the eastern portion of Borneo. It had a population of about 3.03 million at the 2010 census (within the current boundary), 3.42 million at the 2015 census, and 3 ...
, Indonesia.
Habitat degradation
Factors causing
loss of habitat include: conversion of wetlands for agriculture, chemical fertilisers use, use of pesticides in rice production, and an increase in the population of cattle.
The effects of warfare stemming from the conflicts in Vietnam, Laos, and Cambodia during the
Vietnam War
The Vietnam War (also known by other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam a ...
(from land mines to aerial bombardment) have also been factored.
Many river systems, including those in protected areas, have
hydroelectric power dams approved or proposed, which are likely to cause the loss of about half of the remaining breeding colonies within the next ten years.
One cause for
habitat degradation
Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
via hydrological changes, for the Siamese crocodile, is the implementation of dams on the upper
Mekong River
The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...
and its major tributaries.
Potential impacts of dam construction include wetland loss and altered flooding cycle with a dry season flow 50% greater than under natural conditions.
Exploitation and fragmentation
![Farma krokodila](https://upload.wikimedia.org/wikipedia/commons/c/cc/Farma_krokodila.jpg)
Illegal capture of wild crocodiles for supply to farms is an ongoing threat, as well as incidental capture/drowning in
fishing net
A fishing net is a Net (device), net used for fishing. Nets are devices made from fibers woven in a grid-like structure. Some fishing nets are also called fish traps, for example #Fyke nets, fyke nets. Fishing nets are usually meshes formed by ...
s and traps.
The Siamese crocodile currently has extremely low and fragmented remaining populations with little proven reproduction in the wild.
Siamese crocodiles have historically been captured for skins and to stock commercial crocodile farms. In 1945, skin hunting for commercial farms was banned by the French colonial administration of Cambodia.
In the late 1940s, populations spurred the development of farms and harvesting wild crocodiles for stocking these farms.
Protection was abolished by the
Khmer Rouge (1975–79) but later reinstated under Article 18 of the Fishery Law of 1987, which "forbids the catching, selling, and transportation of...
ildcrocodiles..."
Crocodile farming now has a huge economic impact in the provinces surrounding Tonle Sap, where 396 farms held over 20,000 crocodiles in 1998.
Also, many crocodiles were exported from Cambodia since the mid-1980s to stock commercial farms in Thailand, Vietnam, and China.
Despite legal protection, a profitable market exists for the capture and sale of crocodiles to farms since the early 1980s.
This chronic overharvesting has led to the decline of the wild Siamese crocodile.
Conservation
This crocodile is classified as
critically endangered on the
IUCN Red List
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...
, and is listed on Appendix I of
CITES
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
.
It is one of the most endangered crocodiles in the wild, although it is extensively bred in captivity.
The current situation of ''C. siamensis'' represents a significant improvement from the status reported in the 1992 Action Plan (effectively extinct in the wild), but poses major new challenges for quantitative survey and effective conservation action if the species is to survive. While the species remains critically endangered, there is a sufficient residual wild population, albeit severely fragmented across several areas and countries, to provide a basis for recovery.
The Siamese crocodile is relatively unthreatening to people (compared to ''
C. porosus''), and the possibility of people and crocodiles coexisting in natural settings seems possible. The powerful economic force of the commercial industry based on ''C. siamensis'' also needs to be mobilised and channelled for conservation advantage. Considerable effort and action is still required, but the species has a reasonable chance of survival if the necessary actions can be implemented.
Yayasan
Ulin (The Ironwood Foundation) is running a small project to conserve an important wetland habitat in the area of East Kalimantan which is known to contain the crocodiles. Most of them, though, live in Cambodia, where isolated, small groups are present in several remote areas of the
Cardamom Mountains
The Cardamom Mountains ( km, ជួរភ្នំក្រវាញ, ; th, ทิวเขาบรรทัด, ), or the Krâvanh Mountains, is a mountain range in the south west of Cambodia and Eastern Thailand. The majority of the range ...
, in the southwest of the country, and also in the
Virachey National Park
Virachey National Park ( km, ឧទ្យានជាតិវីរជ័យ) is a national park in north-eastern Cambodia covering an area of .
The park is one of only two Cambodian ASEAN Heritage Parks. The park overlaps Ratanakiri and Stun ...
, in the northeast of the country.
In Cambodia
Fauna and Flora International and the Government of Cambodia's Forestry Administration have established the Cambodian Crocodile Conservation Programme for the protection and recovery of Siamese crocodiles. This programme works with a network of indigenous villages who are helping to protect key sites such as Veal Veng Marsh (Veal Veng District), the Tatai River (Thmar Bang District) and the Araeng River. The latter is considered to have the second largest population of Siamese crocodiles in the world, but is currently threatened by the proposed construction of a massive dam in the river. During the heavy monsoon period of June–November, Siamese crocodiles take advantage of the increase in water levels to move out of the river and onto large lakes and other local bodies of water, returning to their original habitat once water levels start receding back to their usual levels.
The Cambodian Crocodile Conservation Programme conducted DNA analysis of 69 crocodiles in
Phnom Tamao Wildlife Rescue Centre in Cambodia 2009, and found 35 of them were purebred ''C. siamensis''. Conservationists from the Forestry Administration and
Fauna and Flora International subsequently launched a conservation breeding program at the Centre. Since 2012, approximately 50 purebred Cambodian Siamese crocodiles have been released into community-protected areas to reinforce the depleted wild populations.
Poaching is a severe threat to this species, with the value of wild Siamese crocodiles reaching hundreds of dollars in the black market, where they are illegally taken into crocodile farms and hybridized with other, larger species. The total wild population is unknown, since most groups are in isolated areas where access is extremely complicated. A number of captively held individuals are the result of hybridization with the
saltwater crocodile, but several thousand "pure" individuals do exist in captivity, and are regularly bred at crocodile farms, especially in Thailand.
Pang Sida National Park in Thailand, near Cambodia, has a project to reintroduce Siamese crocodile into the wild. A number of young crocodiles have been released into a small and remote river in the park, not accessible to visitors.
The Wildlife Conservation Society (WCS) is working with the
government of Laos
The politics of the Lao People's Democratic Republic (commonly known as Laos) takes place in the framework of a one-party parliamentary socialist republic. The only legal political party is the Lao People's Revolutionary Party (LPRP). The head of ...
on a new programme to save this critically endangered crocodile and its wetland habitat. In August, 2011, a press release announced the successful hatching of a clutch of 20 Siamese crocodiles. These eggs were then incubated at the
Laos Zoo. This project represents a new effort by WCS to conserve the biodiversity and habitat of Laos’
Savannakhet Province, promotes conservation of biodiversity for the whole landscape, and relies on community involvement from local residents.
In September 2021, eight hatchlings were found in a wildlife sanctuary in eastern Cambodia.
Priority projects
High priority projects include:
*Status surveys and development of crocodile management and conservation programmes in Cambodia and Laos: These two countries appear to be the remaining stronghold of the species. Identifying key areas and populations, and obtaining quantitative estimates of population size as a precursor to initiating conservation programs is needed.
*Implementation of protection of habitat and restocking in Thailand: Thailand has the best-organized protected-areas system, the largest source of farm-raised crocodiles for restocking, and the most-developed crocodile management programme in the region. Although the species has virtually disappeared from the wild, re-establishment of viable populations in protected areas is feasible.
*Protection of crocodile populations in Vietnam: a combination of habitat protection and captive breeding could prevent loss of the species in Vietnam. A breeding population has been successfully re-established in
Cát Tiên National Park
Cát Tiên National Park ( vi, Vườn quốc gia Cát Tiên) is a national park located in the south of Vietnam, belonging to the area of 3 provinces Đồng Nai, Bình Phước and Lâm Đồng. It is approximately 150 km north o ...
. Further surveys, identification of suitable localities and the implementation of a conservation programme coordinated with the captive breeding efforts of Vietnamese institutions is needed.
*Investigation of the taxonomy of the freshwater crocodiles in Southeast Asia and the Indo-Malaysian Archipelago: The relationships among the freshwater crocodiles in the Indo-Malaysian Archipelago are poorly understood. Clarification of these relationships is of scientific interest and has important implications for conservation.
Other projects include:
*Coordination of captive breeding, trade and conservation in the South east Asian region: Several countries in the region are already deeply involved in captive breeding programs for commercial use. Integration of this activity with necessary conservation actions for the wild populations (including funding surveys and conservation) could be a powerful force for conservation. A long term aim could be the re-establishment of viable wild populations and their sustainable use by ranching.
*Maintain a stock of pure ''C. siamensis'' in crocodile farms: The bulk of the captives worldwide are maintained in several farms in Thailand where extensive interbreeding with ''C. porosus'' has taken place. Hybrids are preferred for their superior commercial qualities, but the hybridisation threatens the genetic integrity of the most threatened species of crocodilians. Farms should be encouraged to segregate genetically pure Siamese crocodiles for conservation, in addition to the hybrids they are promoting for hide production.
*Survey and protection of Siamese crocodiles in Indonesia: Verification of the presence of'' C. siamensis ''in Kalimantan and Java is a first step to developing protection for the species within the context of the developing crocodile management strategy in Indonesia.
Cultural references
A
Malay folktale features a crocodile that is outwitted by a mouse-deer and buffaloes.
A Siamese crocodile has been cited in the
Thai folklore
Thai folklore is a diverse set of mythology and traditional beliefs held by the Thai people. Most Thai folklore has a regional background for it originated in rural Thailand. With the passing of time, and through the influence of the media, large ...
of
Central Thailand's ''
Krai Thong'' ("ไกรทอง") tales have known as well, and was taken to create a television series and movies several times.
A Siamese crocodile stars as the titular monster in the 1978 Thailand film ''
Crocodile''.
References
External links
Crocodylus siamensis– The Crocodile Specialist Group.
Crocodylus siamensis– from the Biodiversity Heritage Librar
Action Plan for Crocodylus siamensis IUCN/SSC Crocodile Specialist Group – Status Survey and Conservation Action Plan, 2nd edition.
*
*
*
{{Taxonbar, from=Q208277
Crocodylidae
Crocodilians of Asia
Reptiles of Southeast Asia
Reptiles of Borneo
Reptiles of Myanmar
Reptiles of Cambodia
Reptiles of India
Reptiles of Indonesia
Reptiles of Laos
Reptiles of Malaysia
Reptiles of Thailand
Reptiles of Vietnam
Critically endangered fauna of Asia
Reptiles described in 1801