Osteolaemus tetraspis

Common names: Dwarf crocodile, broad-nosed crocodile Range: Angola, Benin, Burkina Faso, Cameroon, Central African Republic, Congo, Cte dIvoire, Dem. Rep. Congo, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Nigeria, Senegal, Sierra Leone, Togo

CITES: Appendix I
CSG Action Plan: Availability of Survey Data Extremely Poor
Need for Wild Population Recovery Moderate
Potential for Sustainable Management Low
1996 IUCN Red List: Not Listed (LRlc Lower Risk, least concern, wide distribution and numerous despite extensive local use)
Principal threats: Uncontrolled hunting, habitat destruction.

Ecology and natural history

Dwarf crocodiles range throughout the lowland regions of west and central Africa. This is a little known, diminutive species of crocodilian. Maximum size probably rarely exceeds 2m. Specimens from the upper Congo in Dem. Rep. Congo were described by Schmidt (1919) as a separate genus (Osteoblepharon osborni), but later reduced to the species level (Osteolaemus osborni) by Inger (1948), and subsequently to a subspecies (O. tetraspis osborni) by Wermuth and Mertens (1961).

Waitkuwait (1989) indicates that the dwarf crocodile is primarily a denizen of swamps and swamp forests. It apparently prefers slow moving, calm bodies of water, and frequently utilizes burrows. Some individuals have been reported from isolated pools in savanna habitat, as spending the dry season in burrows (Waitkuwait 1989). In forested areas, dwarf crocodiles are known to make extensive nocturnal terrestrial forays, especially following rains. In many aspects of its ecology this species is very similar to the genus Paleosuchus in the New World. The species is also reported to be able to subsist in isolated forest pools (Waitkuwait 1990). An experimental program in Gambia augmenting the habitat with artificial pools found that small plastic pools were quickly colonized by dwarf crocodile pairs and used successfully for breeding (Jones 1991).

Dwarf crocodiles are mound nesters, with nesting beginning in the early wet season. Females lay small clutches (mean 10) of small eggs, which require approximately 100 days for incubation (Waitkuwait 1989). Breeding physiology is described by Kofron and Steiner (1994). Huchzermeyer and Penrith (1995) suggest that, based on the intestinal morphology, there may be geographic races.

Conservation and status

Basic information is reported from the Cte dIvoire, Gabon, the Central African Republic and Congo. Additional surveys have been conducted in the Gambia, Senegal and Guinea Bissau (Jones 1991) and the CITES West and Central Africa Program has collected anecdotal and market information (Behra 1993a, 1993b). A GIS map of the species distribution has been prepared by the World Conservation Monitoring Center. Because of the lack of systematic surveys, good information on population status of the dwarf crocodile is lacking and in most countries the status is unknown, although it appears to be generally widespread and abundant. Where survey data are available, populations appear to be somewhat depleted. Populations in the Gambia (Jones 1991), on the northern edge of the species distribution, and in Liberia (Kofron and Steiner 1994) are reported to be severely depleted. Countries thought to have major populations, by virtue of their large area and extensive wetlands, are Cte dIvoire, Ghana (Lake Volta), Nigeria (Niger and Benue rivers), Gabon (Ogoue river), Congo and Dem. Rep. Congo (Congo/ Zaire and Ubangi rivers). Angola (Cabinda province), Mali and Senegal are probably the limits of the species range. Pooleys (1982) report of a population in the northern Central African Republic appears discontinuous to the remainder of the range and is in the internal drainage of Lake Chad via the Chari river. It would be interesting to establish if the dwarf crocodile range extends into the extensive marshes of the Bahr Salamat in southern Chad. Distribution of the subspecies O. t. osborni, reported from the upper Congo river remains poorly known.

Habitat destruction (deforestation, wetland alteration) and use for food are the principal threats to this species. Habitat destruction or alteration have been reported in Nigeria, Gambia, Ghana, and Liberia (Pooley 1982). The species is also extensively utilized for meat for local consumption. Sparse data from Congo (Hutton 1991) and Cameroon (Behra 1993a and b) suggest that tens of thousands of dwarf crocodiles are sold in local markets annually for consumption. Some skins are used for the local production of poor quality leather products.

Because of the relatively poor quality of the hide of dwarf crocodiles, intensive commercial hunting has not been a serious problem and there has been little incentive for management programs based on sustainable use. Togo is reported to have a legal harvest system but this program does not appear to be in effect. Congo had a CITES approved quota of 500 in 1987 but did not renew its request for a quota in 1989. Plans are under discussion for the establishment of captive breeding programs for conservation, tourism and possible meat production in Togo, Cameroon (Behra 1993a and b) and Nigeria (Dore 1991). A cooperative study has been established between South African workers and the Congo to examine dwarf crocodile parasites (Huchzermeyer 1993).

Priority projects

High priority

Surveys of the status and distribution throughout west and central Africa: Very few survey data are available from west and central Africa, so the status of this species, although it is widely distributed, remains mostly unknown. Because of the low quality of the hide of Osteolaemus, there is not much incentive for establishing sustainable-yield management programs. However, surveys need to be undertaken in order to determine population status and whether or not appropriate conservation measures should be taken. Because this species is broadly sympatric with C. cataphractus, census work for both species could be combined. Surveys need to be conducted throughout west and central Africa, with priority given to the countries where the species status appears to be most threatened (e.g. Nigeria).

Dwarf crocodile, Osteoleamus tetraspis, juvenile at Zoo National DAbidjan, Cte dIvoire.
Photo by B. Shwedick.