Siamese crocodile

Below is a cladogram based on a 2018 tip dating study using morphological, molecular DNA sequencing, and stratigraphic fossil age data. This was revised in a paleogenomics study using DNA extracted from the extinct Voay. Hall's New Guinea crocodile placement was suggested in 2023. ==Characteristics==

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 measuring and weighing had bite force of . Large male individuals reach and in weight. ==Distribution and habitat==

The Siamese crocodile inhabits a wide range of freshwater habitats, including slow-moving rivers and streams, lakes, seasonal oxbow lakes, marshes and swamps. Since 2000, around 30 sites have been identified in Cambodia that harbour Siamese crocodiles, conservatively estimated to number between 200 and 400 individuals; small population survive in Thailand and Vietnam and in Laos. A small but important population lives in East Kalimantan, Indonesia. ==Behaviour and ecology==

Despite conservation concerns, many aspects of C. siamensis life history in the wild remain unknown, particularly regarding its reproductive biology. 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. There are no recent records in Malaysia, Burma or Brunei. Habitat degradation Factors causing loss of habitat include conversion of wetlands for agriculture, use of chemical fertilisers, pesticides in rice production, and an increase of the cattle population. The effects of warfare stemming from the conflicts in Vietnam, Laos, and Cambodia during the Vietnam War (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. 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 in Cambodia Illegal capture of wild crocodiles for supply to farms is an ongoing threat, as well as incidental capture/drowning in fishing nets and traps. 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, but later reinstated under Article 18 of the Fishery Law of 1987, which "forbids the catching, selling, and transportation of...[wild] crocodiles..." Despite legal protection, a profitable market exists for the capture and sale of crocodiles to farms since the early 1980s. Chronic hunting has led to the decline of the wild Siamese crocodile. ==Conservation==

This crocodile is classified as critically endangered on the IUCN Red List, and is listed on Appendix I of CITES. Yayasan Ulin (The Ironwood Foundation) ran a small project to conserve an important wetland habitat in the area of East Kalimantan which is known to contain the crocodiles. 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. 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 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. In Cambodia's Southern Cardamom National Park, sixty Siamese crocodiles from five distinct nests successfully hatched in July 2024. This marks the largest wild breeding record of the species this century and significantly enhances the survival prospects of this critically endangered reptile. 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. 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. ==References==