The Siamese crocodile is a small, freshwater crocodilian (a group that also includes alligators, caimans and the gharial), with a relatively broad, smooth snout and an elevated, bony crest behind each eye. Overall, it is an olive-green color, with some variation to dark-green. Young specimens measure 1.2–1.5 m (3.9–4.9 ft) and weigh 6–12 kg (13–26 lb), growing up to 2.1 m (6.9 ft) and a weight of 40–70 kg (88–150 lb) as an adult. The largest specimens can measure 3.1 m (10 ft) and reportedly weigh "several hundred kilograms". It is one of the most endangered crocodiles in the wild, although it is extensively bred in captivity.
The historic range of the Siamese crocodile included most of Southeast Asia. This species is now extinct in the wild or nearly extinct from most countries except Cambodia.Formerly it was found in Cambodia, Indonesia (Borneo and possibly Java), Laos, Malaysia, Thailand, Vietnam, Brunei, and Burma.
Siamese crocodiles occur in a wide range of freshwater habitats, including slow-moving rivers and streams, lakes, seasonal oxbow lakes, marshes and swamplands. Most adults do not exceed 3 m (10 ft) in length, although hybrids in captivity can grow much larger. Pure, unhybridised examples of this species are generally unaggressive towards humans, and unprovoked attacks are unknown.
Adults feed mainly on fish, but may also eat amphibians, reptiles and small mammals. Very little is known about the natural history of this species in the wild, but females do appear to 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 20 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.
Three barcode sequences are available from BOLD and GenBank. Below is a sequence of the barcode region cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
Taxonomy ID: 68455
Genbank common name: Siamese crocodile
Inherited blast name: crocodiles
Genetic code: Translation table 1 (Standard)
Mitochondrial genetic code: Translation table 2 (Vertebrate Mitochondrial)
synonym: Crocodylus siamensis Schneider, 1801
Life history and behavior
Despite conservation concerns, many aspects of C. siamensis life history in the wild remain unknown, particularly regarding its reproductive biology.
This crocodile is classified as critically endangered on the IUCN Red List, and is listed on Appendix I of CITES.
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. siamensis are held on commercial crocodile farms in Southeast Asia.
In 1992, it was believed to be extremely close to or fully extinct in the wild. Since then, a number of surveys have confirmed the presence of a tiny population in Thailand (possibly numbering as few as two individuals, discounting recent reintroductions), a small population in Vietnam (possibly less than 100 individuals), and more sizable populations in Burma, Laos and Cambodia. 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 or Brunei. A significant population of the crocodiles is known to be living in East Kalimantan, Indonesia.
Factors causing loss of habitat include: conversion of wetlands for agriculture, using chemical fertilizers, using pesticides in rice production, and an increase in the population of cattle.
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 via hydrological changes, for the Siamese crocodile, is the implementation of dams on the upper Mekong River 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
Illegal capture of wild crocodiles for supply to farms is an ongoing threat, as well as incidental capture/drowning in fishing nets and traps. C. siamensis 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...[wild] crocodiles..."
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 and management
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, dispersed among many areas and countries, to provide a basis for recovery. If the pressures which have caused the virtual disappearance of this species in Thailand, Malaysia and Indonesia can be controlled or reversed, then the species is likely to survive.
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 mobilized 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 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, in the southwest of the country, and also in the Vireakchey National Park, in the northeast of the country.
Fauna and Flora International is running a program in the district of Thmo Bang, Koh Kong province, where villagers are financially encouraged to safeguard known crocodile nests. The Araeng River is considered to have the healthiest population of Siamese crocodiles in the world, although this may soon change after the completion of a massive dam in the river. Fauna and Flora international, in collaboration with several Cambodian government departments, is planning on capturing as many crocodiles as possible from this river and reintroducing them in another, ecologically suitable area, before the completion of the dam and the subsequent flooding of the whole area effectively renders their current habitat unsuitable. 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. A smaller population also is thought to exist in the Ta Tay River, and in the district of Thmo Bang. Poaching is a severe threat to the remaining wild population in the area, with the value of small specimens reaching hundreds of dollars in the black market, where they are normally taken into crocodile farms and mixed 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.
Bang 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 Phnom Tamao Wildlife Rescue Center in Cambodia conducted DNA analysis of 69 crocodiles in 2009, and found 35 of them were purebred C. siamensis. Conservationists from Fauna and Flora International and Wildlife Alliance plan to use these to launch a conservation breeding program in partnership with the Cambodian Forestry Administration.
The Wildlife Conservation Society (WCS) is working with the government of Lao PDR on a new program 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.
High priority projects include:
- Status surveys and development of crocodile management and conservation programs in Cambodia and Lao PDR: 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 program 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 the complete loss of the species in Vietnam. Surveys, identification of suitable localities and the implementation of a conservation program 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 hybridization 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.