Crocodylus porosus

Common names: Saltwater crocodile, salty, estuarine crocodile, Indo-Pacific crocodile, Buaya muara (Indonesia), Baya, Pukpuk, Kone huala (Papua New Guinea), Jara Kaenumkem (Thailand) Range: Australia, Bangladesh, Brunei, Cambodia, China, India, Indonesia, Malaysia, Myanmar, Palau, Papua New Guinea, Philippines, Seychelles (extinct), Singapore, Sri Lanka, Solomon Islands, Thailand, Vanuatu, Vietnam

CITES: Appendix II in Australia and Papua New Guinea
Appendix II in Indonesia (Ranching 3.15 with special conditions)
Appendix I in all other countries
CSG Action Plan: Availability of Survey Data – Variable, Good in Australia and Papua New Guinea, Poor and Extremely poor elsewhere
Need for Wild Population Recovery – High
Potential for Sustainable Management – High
1996 IUCN Red List: Not Listed (LRlc Lower Risk, least concern. Total numbers tens of thousands, numerous localities and extensive range. Population seriously depleted in much of range but secure in Australia and New Guinea.)
Principal threats: Illegal hunting, habitat destruction.

Ecology and natural history

The saltwater crocodile, along with the gharial, is the largest of the living crocodilians, with reported lengths of up to 6–7m. Noted for its large size and fierce disposition, the saltwater crocodile has a reputation as a man-eater. Saltwater crocodiles are the most widely distributed of the crocodilians, ranging from southern India and Sri Lanka, throughout southeast Asia and the Indo-Malay Archipelago, to the Philippines, New Guinea and northern Australia. Isolated populations are also known from the Solomon Islands, the Banks Islands (Vanuatu) and on Palau (Caroline Islands).

A great deal of ecological work has been done on this crocodile in Australia and New Guinea. As the common name implies, in many areas this species is found in coastal brackish water habitats and the tidal sections of rivers. However, the saltwater crocodile is also well known from the freshwater sections of rivers, and also frequents inland lakes, swamps and marshes (Webb et al. 1987, Messel and Vorlicek 1989).

In the tidal waterways of northern Australia the movement of crocodiles between river systems appears to be related to ontogenetic changes in social status as well as the nature of the river’s salinity profile (Messel et al. 1981). Breeding and recruitment take place principally in rivers with significant freshwater input, or in freshwater swamps. As crocodiles grow they encounter larger territorial animals, and many sub-adult crocodiles appear to be excluded from the breeding areas and are forced to occupy marginal habitats such as higher salinity rivers. Mortality among these intermediate-sized crocodiles also appears to be very high.

Females become mature at lengths of approximately 2.2–2.5m (about 12 years of age) and make mound nests during the annual rainy period (Webb et al. 1987). Clutch size is typically 40–60 and incubation normally lasts some 90 days. Nesting is a wet season activity and in northern Australia loss of nests due to flooding is very high. Nest predators include monitor lizards and humans.

Conservation and status

The saltwater crocodile presents a number of challenging problems for the development of conservation programs. It is widely distributed over a vast area including thousands of islands where status and trade are difficult to monitor or control. The saltwater crocodile has the most commercially valuable hide of any crocodilian. Habitat loss associated with coastal development and intensive hide-hunting (from the late 1940s through the 1970s) depleted populations throughout much of the species’ range. Habitat loss continues to be a major problem, and illegal hunting also persists in some areas. Several surveys were conducted in recent years and at least basic survey data are available from 12 countries.

In India, saltwater crocodiles only remain in the northeastern coastal region, and in the Andaman Islands. A restocking program in the Bhitarkanika National Park in Orissa has been quite successful, with over 1,400 crocodiles released by 1993. Surveys in 1994 indicated at least 580 surviving individuals. This population is recovering under active management and protection (Kar 1994). In the Andamans, crocodiles are widely distributed but restricted by the limited areas of freshwater swamp for breeding. Human occupation of these sites is displacing crocodiles (Andrews and Whitaker 1994). The total population of this species in India is estimated at 1,000 (Anon. 1993b). The recent situation in Sri Lanka is considered very serious as there are no conservation or management programs in place.

In Bangladesh, saltwater crocodiles are reported to remain in the Sunderbans (the Ganges delta) (Cox and Rahman 1994).

In Myanmar, (Burma) an unpublished survey by Caughley in 1982 (cited in Aung Moe 1994) estimated 4,000 saltwater crocodiles, mainly in the Irrawaddy delta and in the vicinity of Bogale (=Dalla) river. No recent surveys have been carried out and the surviving number is thought to be less now. A crocodile farm established in 1979 maintains approximately 50 male and 70 female breeders and produces over 1,000 eggs each year. Crocodiles are reported to be exported to Thailand (Aung Moe 1994). An unpublished WWF report identifies crocodile localities at Meinmahal Island, the Arakan and Tenasserim coasts and the Megui Archipelago, all in the Irrawaddy (=Ayarwaddy) delta, which seems to be the remaining stronghold of the species in Myanmar (Van Dink 1993).

Recent crocodile surveys in Thailand (Ratankorn, Amget and Otley 1994) revealed recent sightings of one or two C. porosus on Phuket island but the majority of the suitable habitat in this area has been destroyed or occupied by people and no viable population is thought to persist. Some isolated sections of coastal mangrove habitat may support a remnant population but confirmation by surveys is needed.

Preliminary reports from Cambodia (Thuok and Tang 1994) suggest the species may still occur in small numbers there, although no quantitative estimates or localities were specified and the reports do not clearly differentiate between C. porosus and C. siamensis.

Saltwater crocodiles persisted in southern Vietnam and the Mekong delta until 10 or 20 years ago but recent extensive habitat degradation and direct killing of crocodiles has greatly reduced the population and no more than 100 are thought to survive in the wild (Cuc 1994). Although crocodiles are legally protected, illegal killing is widespread.

In Peninsular Malaysia, the saltwater crocodile is now considered rare. Sebastian (1993) lists 10 localities where crocodiles have been reported and suggests that the Setui- Chalok-Bari basin on the east coast near Trengannu may hold a significant population. In Sabah, C. porosus is reported to be common in the Kinabatangan River and associated wetlands. Stuebing and Mohammed Sah (1992) conducted extensive surveys on the Klias river and found a small but viable population of around 50 individuals that appears to be flourishing. In Sarawak, crocodiles occur in most major rivers and large individuals are sufficiently common to be considered a serious threat to people. In May of 1992, a notorious maneater, the ‘Bujang Senang’, was killed after a 30-year career in which it is said to have eaten 13 people. The animal measured 5.5m in length and weighed more than 900kg (Richie and Johnson Jong 1993). However, earlier surveys (Cox and Gombek 1985) found uniformly low densities of crocodiles throughout Sabah and Sarawak.

In the Philippines, survey information was collected by the Crocodile Farming Institute. Saltwater crocodile populations and habitats are greatly reduced throughout the Philippines and no large populations are known (Ortega et al. 1994). Remaining crocodiles appear to distributed as single individuals and small groups scattered through the remaining habitat. Particular areas of distribution include the island of Mindanao, the Liguasan swamp area, and numerous small rivers around Palawan and northeastern Luzon. Crocodiles have also been recently sighted or captured from Siargo, Negros, Bohol, and Panay (Ortega and Regoniel 1993). On Palawan, the majority of wild adults (141 individuals) are thought to have been caught and moved to the CFI farm where they form the nucleus of a captive population for breeding efforts for commercial use and restocking.

Despite an extensive survey program conducted by FAO and PHPA there is still no reliable estimate of saltwater crocodile populations in Indonesia. The complex geography of the nation makes such a count both extremely difficult and of marginal relevance to conservation. The species is thought to be significantly reduced from historic levels but probably occurs in suitable wetlands on most of the major islands. However, high human densities and past exploitation may have reduced these to remnants in many areas. In the 1994 CITES proposal, 38 protected wetland areas throughout the archipelago were listed where the species is present. Other important localities are the northern swamps of Sumatra and the extensive rivers and lowlands of Kalimantan (Borneo). The species is also widespread in Irian Jaya, particularly in the Mamberano drainage in the north. Standard spotlight surveys in Irian Jaya, Sumatra and Kalimantan have generally shown low counts, but these are thought to be the result of difficult survey conditions rather than low density (Cox 1992). Crocodile conservation and management in Indonesia is undergoing rapid development (Webb and Jenkins 1991a). A system based on cropping and ranching wild eggs, similar to that of Papua New Guinea, is proposed for Irian Jaya, while captive breeding is proposed elsewhere. Persistence of wild populations outside Irian Jaya will probably be dependent on the effectiveness of protected areas. Approximately 20,000 C. porosus are housed on private farms. A combination of licences and permits, harvest regulations (including size limits compatible with the program in Papua New Guinea), internal and international trade controls, and export quotas has been proposed. The Indonesian population of C. porosus was approved for listing on Appendix II ranching in 1994. Export quotas remained zero contingent upon implementation of the proposed management scheme, which was achieved in 1997.

Crocodylus porosus is widely distributed throughout the lowlands of Papua New Guinea and also occurs on New Britain, New Ireland and Manus. A ranching and management program has included regular surveys of representative habitats since 1977. Nesting indices indicate that the population is approximately stable, although showing some reduction (7–12%) in the most recent years (Solmu 1994). However, index levels remain above the baseline levels set in the early 1980s. A review of survey results conducted in early 1995 concluded that the number of nests in the survey areas was steadily increasing (Manolis 1995). Combined harvest levels of eggs, hatchlings and wild skins (another index of population trends) have fluctuated around 5,000 per year since 1990. The Papua New Guinean management system, involving a combination of wild cropping, egg and hatchling harvest and ranching, appears to be maintaining the crocodile population. Residual concerns remain about the unknown extent or effect of habitat disruption and pollution (for example by upstream lumbering and gold mining) and the status of isolated populations in eastern Papua New Guinea and the offshore islands. Given the very large area of inaccessible and undeveloped habitat (in excess of 50,000km² ) and the incentives for local traditional landowners to maintain crocodiles, the species seems secure in Papua New Guinea.

Surveys by Messel and colleagues established the baseline for crocodilian management and recovery in Australia (Messel et al. 1978–1987). Australia has undertaken a major development of its crocodile management strategy with transfer of the Australian population in 1994 to Appendix II under the Berne Criteria (Anon. 1994d). In the Northern Territory, surveys conducted annually since the early 1970s indicate continuing population recovery despite high levels of the removal of eggs for sustainable use programs. Total population and population size and age structures are thought to be approaching pre-exploitation levels (Webb et al. 1994). A sustainable use program based on ranching of wild collected eggs forms the basis of management, combined with an aggressive program of problem crocodile removal and public education to reduce conflicts with people. In Queensland, heavy occupation by people of the eastern coastal lowlands has reduced crocodile populations, and in recent years problem crocodiles have been removed to farms. However, substantial populations remain in northern and western Cape York Peninsular and Princess Charlotte Bay. Surveys are underway to assess population numbers and a conservation plan has been prepared to maintain populations in protected areas (Anon. 1994c). In Western Australia, major populations in the northwest are in protected areas and small scale use by native peoples occurs. There are three farms supported by captive breeding, ranching eggs and problem animal removal. Australia seems sure to be the major stronghold of the species into the future.

A crocodile survey of the Solomon Islands was conducted in 1989 (Messel and King 1990). Suitable habitat is restricted by the terrain and further reduced by human occupation and agriculture. Three localities, Lauvi lagoon (Guadacanal), Lake Tatae (Russells Is.) and Ghahirahobo (Santa Isabel) support small populations with widely scattered stragglers occurring elsewhere. Total number of non-hatchling crocodiles is in the order of 200. Twelve ‘farms’ hold a total of 131 captive crocodiles, but none of the farms are set up for captive breeding. Crocodiles in the Solomons were greatly depleted by hunting for skins up until 1989 and continue to be killed by local people who consider crocodiles vermin. Recommendations for complete protection and continued monitoring were made.

Palau (Caroline Islands) supported extensive exports of crocodile skins between 1965 and 1981. In 1991, Messel and King conducted a survey and investigated historical and local records concerning which species were present (Messel and King 1992a). They concluded that there is no historical or biological support for the presence of any species on Palau except Crocodylus porosus (Messel and King 1991). Night surveys revealed 42 crocodiles in 112km of surveyed waterway, concentrated in two small populations at North Estuary on Belilou and Ngerdok Lake, Babeldaob. Additional small groups and single sightings were made at Ngeremeduu Bay, Kadebel river, Irur and Iwekei rivers (Babeldaob) and in the Rock Islands. The species is nearing extinction on Palau following a prolonged eradication program through the 1960s into the 1980s. Total population is probably less than 150 and no evidence of recent breeding was seen. A recovery plan has been drafted by the US Fisheries and Wildlife Service proposing the acquisition of critical habitat, protecting breeding areas, increased enforcement to prevent crocodile killing and the establishment of a public education program (Brazaitis 1994).

The eastern-most population of C. porosus is recorded from eastern Vanua Lava in Vanuatu (New Hebrides and Banks Islands). The locality was surveyed in 1992 by Messel and King (1992b), who concluded that crocodiles were on the verge of extinction there. Only two adult crocodiles were seen in the wild and the population is no longer breeding.

Stray saltwater crocodiles have been encountered far distant from their normal range. Takashima (1955) reports three crocodiles from Japanese territory; one from Iwo Jima (in 1744), one from Amami-Oshima at the northern end of the Ryukyu Islands (in 1800), and a third from Toyama Bay, on the main Japanese island of Honshu. All three were presumably specimens of C. porosus. A vagrant was recently reported on Nauru Island (Webb 1994). Re-examination of skeletal material from the Seychelles suggests that the crocodile that occurred there at the time of European discovery, and subsequently extirpated by the 1800s, was C. porosus and not C. niloticus as previously assumed (Gerlach and Canning 1993). The continued presence of C. porosus in southern China remains to be verified.

Populations of the saltwater crocodile are legally protected in most countries, but this protection is often ineffective. Sustainable utilization management programs have been successfully implemented in Papua New Guinea and Australia. The establishment of the management program in Papua New Guinea was a milestone in crocodilian conservation, and a similar project is now being attempted in Indonesia. In both countries, utilization is based principally on the direct cropping of wild animals, but ranching forms an important and growing component. Farming of C. porosus is being done on a large scale in Thailand and Australia, and on a smaller scale in Papua New Guinea. Farms are also under development in Cambodia, Vietnam and Lao PDR.

As a species, the saltwater crocodile is most unlikely to become extinct due to the large populations, extensive habitat and effective management and protection in Australia, Papua New Guinea and possibly Indonesia. However, if present trends continue it seems likely to disappear or become extremely rare throughout the remainder of its range, perhaps persisting only in small protected pockets like Sarawak and the Bhitarkanika Preserve in India. It is ironic and possibly instructive, that in the countries where the species is heavily, but sustainably used, it is secure, but in the countries where it is completely, but ineffectively, protected, it may disappear.

Priority projects

High priority

Population censuses in unsurveyed countries: Quantitative information on the status of C. porosus populations is lacking for many countries where this species occurs, and within most of the other countries large areas remain unsurveyed. Population surveys need to be conducted in Burma, Cambodia, peninsular Malaysia, Vietnam, Brunei, Sri Lanka, Philippines. Follow up surveys and monitoring, in association with conservation and management programs should be developed for Thailand, Indonesia, Sabah and Sarawak.

Implementation of the Indonesian management program: A sustainable utilization management program is currently being set up by Indonesian wildlife personnel with assistance from the CSG. A crocodile monitoring program is being established and technical support for ranching and farming activities is being offered. Five main points need to be addressed:

1. Implementation of the management and regulatory program and trade control.
2. Population monitoring in areas already censused and initiation of surveys in new areas, including identification of principal nesting habitats.
3. Licensing and reporting of captive breeding operations.
4. Implementation of a conservation awareness campaign at the village level.
5. Protection of remnant populations in protected wetlands outside Irian Jaya.

Establishment of management and conservation programs in Cambodia and Vietnam: The close association of the production and trade in crocodilian products between Cambodia, Vietnam and Thailand suggests that management, conservation and regulatory activities need to be coordinated in the Indo-Chinese region. Thailand is well advanced in practical husbandry development and has already invested in farm development in the other countries. Technical exchange for training programs, surveys, management plan development and mutually supporting regulatory structures are recommended.

Moderate priority

Indian management program: As with the mugger crocodile, the saltwater crocodile captive breeding program has been a victim of its own success. Evaluation of restocking and identification of additional release sites need to be included in the crocodile conservation program to relieve some of the excess of animals that are now in captivity. A program needs to be developed to deal with “nuisance” crocodiles in the Bhitarkanika Park and other areas.

Development of sustainable management programs in Malaysia: Whitaker (1984) recommended the establishment of a conservation program based on Sustainable Use for East Malaysia (Sabah in particular). The program would be based on the establishment of a government demonstration ranch, the encouragement of private sector involvement in ranching, establishment of an egg collecting/nest monitoring program involving local villagers, the trapping of nuisance crocodiles for farm breeding stock, the protection of crocodile breeding habitat, and a public education program.

Saltwater crocodile, Crocodylus porosus, Northern Territory, Australia. In Australia this
species has recovered substantially from earlier exploitation and is the subject
of an intensive monitoring, management and use program. Photo by D. Jelden.