Crocodylus siamensis

Common names: Siamese crocodile, Buaya kodok (Indonesia), Jara Kaenumchued (Thailand) Range: Thailand, Cambodia, Vietnam, Indonesia, Lao PDR, Malaysia (Sabah, Sarawak)

CITES: Appendix I
CSG Action Plan: Availability of Survey Data – Poor
Need for Wild Population Recovery – Highest
Potential for Sustainable Management – High
1996 IUCN Red List: CR Critically Endangered. Criteria A.1.a. and c. severe decline in numbers and area >80% decline in three generations.
Principal threats: Habitat destruction, illegal hunting.

Ecology and natural history

The ecology of the Siamese crocodile in the wild is virtually unknown. According to Smith (1919, 1931), the preferred habitat of this species is freshwater swamps and slow-moving sections of streams and rivers, but it was also found in lakes and rivers. Maximum size of males has been reported to be up to 4m, but most individuals do not exceed 3m. All our information on reproduction in this species has come from captive individuals. Females construct a mound nest during the annual wet season and lay 20–50 eggs (Youngprapakorn et al. 1971). Recent information is available on the chromosome number of C. siamensis and hybrids with C. porosus (Youngprapakorn 1991, Chavananikul et al. 1994), and seasonal sperm cycles (Kitiyanant et al. 1994).

Conservation and status

The Siamese crocodile was regarded as one of the world’s most endangered crocodilians and was reported in 1992 as virtually extinct in the wild. Following the identification of this species as the highest priority for conservation action, considerable new information on its present distribution was collected. However, quantitative assessments of its status in the wild are still completely lacking.

In Thailand, a survey conducted in November 1993 confirmed the presence of at least one wild adult C. siamensis in Pang Sida National Park and another in Ang Lue Nai Wildlife Sanctuary (Ratanakorn et al. 1994). Both of these individuals are reported to live in small areas of suboptimal habitat. Indirect indications (tracks and slides) of other single specimens are reported at Yod Dome and Sanam Chai Kate (Kreetiyutanont 1993, Ratanakorn and Leelapatra 1994). The remnant population formerly reported in Bung Borapet is apparently extirpated due to illegal capture for farms and mortality in net fisheries, although there are plans by the Royal Thai Forest Service and Department of Fisheries to restock a seminatural captive population there. The status of C. siamensis in Thailand therefore appears to be reduced to non-breeding remnants in marginal habitats and it is almost extinct in the wild.

Reports on trade of small Siamese crocodiles into Thailand from Cambodia (Frazier 1991, Chea and Ratanakorn 1993) prompted further contacts and investigations which were facilitated by the improved political situation in Cambodia. Thuok and Tana (1994), report 14 localities in Cambodia where crocodiles (presumed to be mostly C. siamensis) are found, and indicate that there are 172 ‘farms’ producing over 10,000 hatchlings per year. Wild crocodiles are reported to be diminishing their range and numbers due to human disturbance and habitat occupation, and to be restricted to inaccessible swamps in the hinterland. Particular concentrations are said to occur in flooded forests near Battambang and Siem Reap around the Tonle Sap (Great Lake), in the vicinity of Stung Treng on the upper Mekong, and in Preach Vihea swamp near Tbang Mean Chey on the upper Sen river. Populations of wild individuals were estimated to be from 50–300 up to 1,000–4,000 at specific locations, although the basis for these estimates is not given and they require confirmation.

In Lao PDR, Siamese crocodiles are said to still occur in a number of locations along the Mekong, but population levels are low and crocodiles have disappeared from several areas (Sawathvong 1994). Based on interviews conducted in villages from 1988 to 1993, 20 specific localities were identified of which five were said to support significant populations, but crocodiles are reported as rare or possibly extirpated from seven. In Vietnam, Cuc (1994) reports that Siamese crocodiles were once widely distributed throughout major rivers, lakes and swamps in southern Vietnam. Massive habitat conversion to agriculture, environmental degradation and aggressive hunting with guns, traps and explosive mines, have greatly depleted all populations. According to local informants no more than 100 individuals survive in the wild. The presence of C. siamensis has not been confirmed in peninsular Malaya or Sarawak and Sabah in recent times (Sebastian 1993) and it may be extirpated there.

Museum specimens suggest that C. siamensis was formerly found in Indonesia on Borneo (Kalimantan) and Java ( Ross 1986). The report of Cox et al. (1993) that C. siamensis held in farms in Kalimantan (Indonesia) were captured from rivers there, remains the only recent verification of the species in Indonesia.

The Mekong river basin and associated wetlands in Cambodia and Lao PDR appear to have the only remaining large wild populations of C. siamenis left, although these are fragmented and depleted.

The species is extensively maintained and bred in captivity in Thailand and Cambodia, and to a lesser extent in Vietnam, Lao PDR and Indonesia. Zoos in North America hold 132 specimens and in Europe 7 specimens. Captive breeding has also been accomplished in Russia (Moscow and Rostov zoos) and in Japan (Higashi-Izu zoo) (Honegger and Hunt 1990). The Thai captive population includes numbers of hybrids with C. porosus. The hybrids are fertile and F₂s and backcrosses to both parents are reported (Chavananikul et al. 1994). Hybrids with introduced C. rhombifer are also reported in Vietnam (Thang 1994). However, the captive population of pure C. siamensis, which numbers many thousands in hundreds of facilities, provides a significant resource for conservation. Linking commercial incentives from captive propagation to conservation of wild populations will be the most significant component in the conservation of the species. Thailand has taken the lead in this development and two associations involving crocodile farmers and other interested persons were formed, the Crocodile Management Association of Thailand (CMAT) in 1990 and the Thai Association of Traders in Reptiles and Amphibians (TATRA) in 1993. Following CITES sanctions on the Thai wildlife trade in 1991 due to poor CITES implementation, two CSG members conducted a technical visit (Webb and Jenkins 1991b) and two reviews (Jelden and Messel 1992, Anon. 1994f). These interventions generated recommendations for crocodilian management, including adoption of legislation and regulations, surveys, control of illegal trade, regional conservation initiatives and a restocking program. Thai authorities, in conjunction with CMAT, TATRA and neighboring countries, are proceeding with the implementation of these recommendations, and a National Crocodile Management Plan has been drafted (Ratanakorn and Leelapatra 1994). Management recommendations for the species in Indonesia are presented in Messel et al. 1992.

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 co-existing in natural settings seems possible. There is also the powerful economic force of the commercial industry based on C. siamensis which 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.

Priority projects

High priority

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. The clarification of these relationships is not only of scientific interest but also has important implications for conservation.

Moderate priority

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 captive C. siamensis 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 one of the most threatened species of crocodilians. Farms should be encouraged to segregate genetically pure C. siamensis 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.

Siamese crocodile, Crocodylus siamensis. New reports of wild populations in Cambodia
and Vietnam offer some hope for the conservation of this Critically Endangered species.
Photo by G. J. W. Webb.