Tomistoma schlegelii

Common names: Tomistoma, false gharial, Buaya sumpit (Indonesia), Takong (Thailand) Range: Indonesia, Malaysia, Thailand (extirpated)

CITES: Appendix I
CSG Action Plan: Availability of Survey Data – Extremely Poor
Need for Wild Population Recovery – Highest
Potential for Sustainable Management – Low
1996 IUCN Red List: DD Data Deficient. Possibly CR Critically Endangered or EN Endangered, remaining populations suspected to be very small and highly fragmented. (Newly obtained information in Sumatra and Borneo will allow re-evaluation of status)
Principal threats: Habitat destruction.

Ecology and natural history

The tomistoma or “false gharial” is one of the most unusual and little known of the crocodilians. It is a large species, with males attaining sizes of up to 5m, and has a distinctive narrow snout marked with dark blotches. The historic range of the species includes the Malay Peninsula (southern Thailand and Malaysia), Sumatra and Borneo (Indonesia, Malaysia). A report of the species in Sulawesi and Vietnam (Groombridge 1982) remains unsupported.

Little is known about the ecology of this species in the wild. Tomistoma appears to be restricted primarily to freshwater swamps, rivers and lakes and may occasionally use burrows. Slow-moving water and heavily vegetated habitats seem to be preferred. Females are mound nesters, and lay clutches of 20–60 very large eggs. Sexual maturity is attained among females at a length of 2.5–3m (Groombridge 1982, Bezuijen et al. 1997).

The evolutionary relationship of Tomistoma with other crocodilians has been a subject of recent debate, and no consensus has been reached. Traditionally, Tomistoma has been closely aligned with the true crocodiles (Crocodylidae) based on morphological evidence (Tarsitano et al. 1989). Biochemical and immunological studies, however, suggest that Tomistoma is more closely related to the gharial (Gavialidae) (Densmore and Owen 1989). Poe (1996) summarises the arguments and supports the latter.

Conservation and status

Since the publication of the first edition of the Action Plan (1992), new information has become available concerning the distribution of wild populations of Tomistoma. Early surveys were restricted to Sarawak, where numbers were extremely low. Whitaker (1984) surveyed Sabah, East Malaysia, but considered this area to be outside of the natural distribution of Tomistoma. Sebastian (1994) summarized information collated by the Asian Wetland Bureau on wetland areas and reported 26 confirmed locations in peninsular Malaysia, East Malaysia (Sarawak), Kalimantan and Sumatra. Additional unconfirmed reports from Marisa river, north Sulawesi, and Ca Mau, Minh Hai Province, Vietnam, would be significant range extensions if verified. There have been no records of Tomistoma in Thailand since 1970 and it is probably extirpated there (Ratanakorn et al. 1994).

Major centers of distribution are in Indonesia. Following the identification of Tomistoma as a major priority in the 1992 Action Plan, a CSG research program was initiated (coordinated by G. Webb and colleagues) that has produced a significant expansion of our knowledge of this species in Sumatra. Prior to the 1950s, Tomistoma appears to have occurred from southeastern Aceh province to southern Lampung province. Intensive hunting in the 1950s–1970s and increasing human use of habitats has reduced this range by approximately 30%. Currently, tomistoma are thought to occur from southeastern Sumatera Utara province to southern Sumatera Selantan province with an isolated population in Way Kambas National Park, Lampung Province. Western limits to the range are probably the foothills of the Barisan Mountain Range (Bezuijen et al. 1997). Detailed studies have been conducted on breeding populations in Sumatra, in the Lalan and the Merang river and Berbak National Park (Bezuijen et al. 1995, 1997). Densities by spotlight survey were 0.18–0.26 individuals/km. Details of reproductive biology and habitat use are presented. In Kalimantan, Frazier and Maturbongs (1990), and Muin and Ramono (1994) report Tomistoma in East Kalimantan province and west of Samarinda, in the southwest of Kalimantan-Tenga province, including Tanjung Puting National Park, and in Kalimantan Barat in Danau Sentarum Wildlife Preserve. Ross et al. (1996) and Meijaard and Sozer (1996) provide additional recent sighting records and observations from the upper Mahakam river, Timur Province and Kalimantan Tengah province in Kalimantan. Tomistoma is said to be the most abundant freshwater crocodile in some of these areas.

In Malaysia, tomistoma are reported from Western Sarawak, and in peninsular Malaysia in Selangor swamp, the Pahang river and in Tesak Besra National Park. Status in Malaysia is unknown, but tomistoma appear to be quite rare and limited in distribution. A preliminary survey in Tesak Besra in 1997 did not record any Tomistoma.

These recent surveys have greatly expanded our information on the distribution of Tomistoma, although estimates of population numbers remain uncertain. There appear to be numerous locations in Indonesia where conservation projects for Tomistoma would be advisable. Nearly half of the recorded localities occur within protected areas, but the level of protection is often ineffective. Current threats are habitat loss by conversion of riparian habitat (dams, flood mitigation, channelling, de-forestation), and net fishing, which causes direct mortality and may deplete food sources for Tomistoma. The habitat needs of Tomistoma may be specific for floating vegetation mats and shady streamside vegetation. Examination of these requirements and design of suitable conservation and management within protected areas is desirable.

Captive Tomistoma are held by numbers of private facilities in Kalimantan, Sarawak and Thailand, as well as in European and US zoos. Jong’s Crocodile Farm, Kuching, Sarawak, has 10 adults and 29 juveniles, while Samutprakan Crocodile Farm in Thailand has several large subadults. Successful captive breeding has been achieved in an Indonesian farm and in zoos in USA, and Europe.

Priority projects

High priority

Status surveys in Malaysia and Indonesia: Quantitative surveys to establish the extent and size of the various reported populations in Sumatra, Kalimantan, Sarawak and Malaysia are needed. These should be conducted in conjunction with national authorities to identify the areas occupied, conservation threats and conservation actions needed.

Development and implementation of conservation and research programs: Following initial survey work, conservation plans for this species need to be drawn, particularly in Indonesia and Malaysia where Tomistoma is most widely distributed. Habitat protection measures should be undertaken and ecological investigations, including population monitoring, initiated. Identification of special habitat needs and the incorporation of appropriate land management regimes to preserve these needs should be included.

Moderate priority

Verification of two outlying records: Reported presence of Tomistoma in southwestern Vietnam and Sulawesi Island should be investigated.

The tomistoma, Tomistoma schlegelii. Courting pair photographed in captivity at Florida
Cypress Gardens. Surveys of this species in Indonesia and Malaya initiated as a result
of the first Action Plan for Crocodiles 1992 have resulted in significant new information
about the distribution and biology of this species. Photo by B. Shwedick.