Melanosuchus niger

Common names: Black caiman, Jacaré assu (also açu, uassu, guaçu), Jacaré negro, Caimán negro, Caimán, Cocodrilo Range: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru Revised by John Thorbjarnarson

CITES: Appendix II in Ecuador (ranching) subject to quota from 1997; Appendix I in all other countries.
CSG Action Plan: Availability of Survey Data – Poor
Need for Wild Population Recovery – High
Potential for Sustainable Management – Moderate
1996 IUCN Red List: EN. Endangered. Criteria A.1.c. d. Inferred decline >50% in 3 generations, exploitation over much of range. Current recovery may be trending toward Vulnerable.
Principal threats: Illegal hunting, habitat destruction.

Ecology and natural history

The black caiman is the largest member of the Alligatoridae, with adult males surpassing 4m in length. This species is widely distributed throughout the Amazon River basin, but populations are also known from peripheral areas outside the Amazon (the Rupununi and upper Essequibo River drainage in Guyana; the Kaw region of French Guyana; Vasquez 1991). Until recently the black caiman had been little studied. However, during the 1980s research on wild and captive populations was carried out by Herron and collaborators (1985, 1990, 1991, 1994) in southern Peru, Pacheco (1990a and b, 1993a and b, 1994) in Bolivia, and Asanza (1985, 1992) in Ecuador. Ecological studies are presently being carried out in Brazil (Sociedade Civil Mamirauá), Ecuador (EcoCiencia), and Colombia (Universidad Nacional de Colombia). Additionally, information on aspects of the ecology of this species was gathered during survey work conducted by Brazaitis et al. (1990a and b), and King and Videz-Roca (1988). Hines and Rice (1992, 1994) have conducted recent surveys of population status in Ecuador. Gorzula and Woolford (1990) surveyed black caiman in the Essequibo region of Guyana. These studies have augmented the work done by Medem on this species in Colombia throughout the 1950s, 1960s and 1970s (Medem 1981), and the studies of Otte (1978) in Peru.

The black caiman occupies a wide variety of habitats including large rivers and streams, oxbow lakes, and in some areas seasonally flooded savannas. Ecological habitat partitioning between this species and the other Amazonian caimans appears to be taking place in many areas, but habitat relations among the species have been blurred by the severe reduction in numbers of black caiman in most areas (Magnusson 1982). Herron (1994) found that common caiman and black caiman were spatially separated in a Peruvian oxbow lake. Fittkau (1970) hypothesized that black caiman played a vital role in nutrient cycling in the rivers and mouth-lakes of the lower Amazon. The demise of Melanosuchus populations has been linked anecdotally with a decrease in fisheries productivity. However, little ecological evidence is available to confirm or refute these ideas. Peres and Carkeek (1993) provide an interesting account of how large caiman populations in the Brazilian Amazon protect fish stocks by destroying fishing nets.

The black caiman, like all alligatorids, is a mound nester, however, many aspects of this species’ reproductive ecology are poorly known. Available information suggests that females reach sexual maturity when ca. 200cm total length (TL). Mean adult female size is 280cm TL, and clutch size averages 39.3. Melanosuchus lays very large eggs averaging 143.6g (Thorbjarnarson 1996). Herron et al. (1990) report on a Melanosuchus nest in Peru observed throughout the entire period of incubation. Pacheco (1990a and b) presents information on the reproduction of captive Melanosuchus in Bolivia.

Conservation and status

Commercial hunting of the black caiman did not begin in earnest until the 1940s, when stocks of the South American crocodiles (Crocodylus acutus, Crocodylus intermedius) were becoming very low. Hunting peaked during the 1950s, and declined markedly through the 1960s, when trade in Caiman crocodilus began to increase. However, in some areas significant trade in black caiman extended into the 1970s (Plotkin et al. 1983, Gorzula and Woolford 1990). Commercial hunting continues to be a problem in some areas. In the upper Amazon of Brazil, most hunting is for the sale of meat which is reportedly sold in Pará or Leticia. Ecological competition with the smaller common caiman may also be playing an important role in slowing natural population recovery (Magnusson 1982, Brazaitis et al. 1988).

Some recent census work has been conducted throughout most of the range of the black caiman. Although it is widely distributed (principally in the Amazon basin) past overhunting and continued poaching has drastically reduced populations. Populations of black caiman are considered to be severely depleted in four of the seven nations in which the species occurs, and are depleted in the remainder. Relatively good populations remain scattered in isolated areas of Guyana, Peru, and Ecuador, particularly in oxbow lakes and other marshy, non-riverine wetlands where access is difficult. The population in the Kaw region of French Guiana has been decimated by hide hunting, and in Bolivia and Colombia black caiman appear to be still widely distributed, but occur in low numbers. Some Brazilian populations are locally dense but in most areas they represent but a small fraction of their former levels. While commercial exploitation has been illegal and minimal in recent years, people throughout the region continue to utilise black caiman for other purposes. The fat is collected for medicinal purposes and the meat is reportedly used to bait traps for edible tortoises. For human consumption, the meat of black caiman is considered rank and, in comparison to the meat of Caiman and Paleosuchus, is poorly regarded by indigenous people, (Ortiz van Halle 1995, Alvarez 1995).

Ecuador is initiating a trial ranching program. In all other countries management programs for the black caiman are exclusively based on the legal protection of wild populations. However, as in the majority of developing countries, the enforcement of these laws is difficult.

Columbia

Black caiman were at one time abundant in the Colombian Amazon region from the southern city of Leticia to the Río Atacuari along the border with Peru, and in the Putumayo, Caquetá, and lower Apaporis rivers (Medem 1981; Plotkin et al. 1983). Commerial hide hunting began in the 1940s and populations were rapidly depleted. Wild populations of black caiman have been virtually extirpated in Colombia. Surveys by biologists in the 1970s found very few individuals in the Amazon and Putamayo region (Medem 1981, Plotkin et al. 1983). Based on interviews in the vicinity of Leticia, Pachon and Rios (1993) believe that little hunting is currently taking place and populations are slowly recovering. However, only three adults were seen during five diurnal foot surveys, and none were observed during nocturnal counts by boat. Additional surveys and ecological studies were planned for 1994–95.

Melanosuchus were legally protected in Colombia in 1969 with the implementation of a total ban on hunting (Resolution No. 411). Hunting and egg collection is also specifically banned for Melanosuchus (INDERENA Resolution No. 573 of 1969; Plotkin et al. 1983), but little enforcement has been in effect and significant commercial hide hunting continued into the 1970s. Recently, it has been reported that Melanosuchus has been removed from the list of totally protected species because population status was judged to be secure in well protected habitat (Jenkins et al. 1994). One farm was reported to be registered for experimental captive breeding of black caiman (breeding stock 2 males, 8 females in 1994). However, INDERENA officials have stated that commercial exploitation would not begin before a wild population monitoring program was established and the farm registered under CITES regulations (King 1994).

Ecuador

In Ecuador, Asanza (1992) reports that Melanosuchus was heavily exploited between 1930 and 1970, with approximately 500,000 skins being traded, mostly through Leticia and Manaus. In the 1970s, Medem (King 1973) believed that Ecuador was the only place where Melanosuchus was not on the verge of extinction. Populations are known to exist in several parts of the Ecuadorian Amazon, particularly in isolated oxbow lakes. Miyata (in Groombridge 1982) reports that the species may be relatively common in the lower Río Aguarico and the Río Yasuni-Lagartococha area near the Peruvian border. The Zancudococha population appears to be a healthy one with an estimated population size of 100 to 150 (Jahoda 1990, Bowes 1992); however, based on two years’ census data, Asanza (pers. comm.) estimated the total population size to be 260, with a mean density of 23/ km. Asanza (1992) reports that significant populations are still found in the Aguarico River system (Cuyabeno lakes and river, Imuya Pacuya and Zancudococha lakes, and the Cocaya River), the Napo River system (Jivino, Indillana, Tipitini and Yasuni rivers, and Limoncocha, Taracoa, Arango, Challuacocha, Panacocha, Garzacocha and Jatuncocha lakes), the lower Nashino and Cononaco rivers, the lower and middle Curaray River, the lower Pindoyacu, the lower Yaupi and upper Morona, and the Pastaza River system (Bufeo, Capahuari, and lower Ishpingo rivers). Population densities in the Cuyabeno region have been relatively stable since 1978, with mean values of 5.68/km in the lakes and 3.15/km in the lakes and rivers. Densities in Zancudococha (23.5/km) and Lagartococha (23.6/km) lakes have been high based on five and two years of surveys respectively. However, Asanza (1992) reports a decline in the population of Melanosuchus in Limoncocha between 1983 and 1990.

Hines and Rice (1992, 1994) conducted caiman censuses in Ecuador during 1992 and 1993 along 18 survey routes (131.2km total) of optimal habitat. Black caiman were observed at 16 of 17 locations and densities ranged from 0/km to 13.25/km, with a mean value of 4.65/km. The highest densities were found at Challuacocha (11–13/km), Lagartococha (up to 13.25/km), and Limoncocha (10.25/km). In a total of 28 surveys, 309 Melanosuchus and 188 Caiman were observed. The size class distribution reflected an abundance of juvenile animals.

The black caiman was not protected in Ecuador by the wildlife resolution of 1970, but is included in the total ban on export of commercial wildlife (Plotkin et al. 1983). Asanza (1982) reports that Decreto 487 (of 1980) and Ley No. 74 (1981) prohibit the commercial hunting of all reptiles and the export of indigenous species. The population in Limoncocha is protected as result of the site being a research station. Efforts are underway to have the Zancudococha lagoon included in the national park system, and a biological station similar to the one on Limoncocha established (Asanza, pers. comm.). In 1995–6, population surveys and ecological research on black caiman in and around the Yasuni National Park were planned by EcoCiencia, an Ecuadorian NGO, as part of the SUBIR (Sustainable Use of Biological Resources) project.

In the late 1980s, an illegal trade in small (40–120cm TL) live Melanosuchus was reported. Although their final destination is unknown, numbers of these animals were reported to be illegally exported over the Colombian and Peruvian borders (Asanza, pers. comm.). At the 1994 CITES meeting, a ranching program for Melanosuchus in Ecuador was approved. This program will be managed by the government wildlife management authority INEFAN. However, due to questions pertaining to the readiness of the management program, a two-year zero-export quota was voluntarily agreed to by the Ecuadorian authorities. Ecuador has drafted a management plan for the ranching program, and assigned an INEFAN representative to manage it. A three-year trial program will collect a maximum of 1,500 eggs and/or hatchlings per year, with only one company licensed to participate. INEFAN and the company will jointly conduct population monitoring. All captive animals will be tagged, and exported skins will not exceed 2.2m in length. Provisions will also be made to permit export of live animals (up to 15% of the export quota, of one sex only).

Peru

Plotkin et al. (1983) considered the black caiman to be on the verge of extinction in Peru. Historically the species was common throughout the upper Amazon drainages in Peru, but was depleted by hunting which began around 1950 (Plotkin et al. 1983). Surveys by Otte (1974) found no Melanosuchus along the Sotileja, Heath and the Pariamanú Rivers, but some black caiman were observed in the upper Río de las Piedras. Based on information from caiman hunters and skin buyers, Otte (1974) concluded that exploitable populations were only found in the upper regions of the Tambopata, Manú, Piedras and Amigo Rivers. More recently, viable populations were observed in lagoons along the Tampopata River (Plotkin et al. 1983), and some evidence suggests that populations may be recovering in the Manu-Madre de Dios region. Population surveys have been conducted in Cocha Cashu in Manú National Park since the early 1970s. Otte (1974) estimated a population size of 37 in 1971–1972. Similar counts carried out in 1978 suggested a 50–60% increase in population size. A census in 1982 estimated population size to be 213 (Vasquez 1982–3). During nocturnal counts in Cocha Cashu (4.0km) by Herron (1985), 99–111 black caiman were sighted (uncorrected population estimate; density = 24.74–27.75/km shoreline), with a population heavily skewed towards juveniles. Researchers studying otters in the Manu region indicate that the park contains a good population of black caiman, with smaller numbers being found in the Madre de Dios River, the Rio de los Amigos, the Rio de la Torre, the Rio Tambopata, and the Rio Heath (C. Schenck and E. Staib, in litt., 6 August 1993). In the Manu park, black caiman were seen in the cochas (oxbows) of Cashu, Lagarto, Brasco, Salvador, Huarez and Garza.

Another small population remains in the Pacaya-Samiria National Reserve. Nocturnal counts in the Samiria river found a mean Melanosuchus density of 0.28/km (Verdi et al. 1980). During the early 1970s, Vasquez (1981) conducted nocturnal counts of black caiman in the Jenaro Herrera region and found densities of 0.46/km in lake habitat to 3.11/ha in swamp areas (4.5ha surveyed). Vasquez (1982–3) suggests that Melanosuchus populations have recovered to some degree since the decline in illegal hide hunting.

Hunting of black caiman is prohibited in all cases except for subsistence purposes, although in some areas illegal commercial hunting continues (Plotkin et al. 1983). Ecological studies of Melanosuchus in the Manu region have been conducted by Otte (1978), Herron (1985, 1991, 1994) and Herron et al. (1990).

Bolivia

Black caiman were historically widespread throughout northern and eastern Bolivia, but were heavily impacted by hide hunting during the period 1942–1960 (Plotkin et al. 1983). Surveys in 1986–1987 found black caiman to still be distributed throughout most of its historical range, but in very low numbers (King and Videz Roca 1989). Of the very few individuals that were encountered, most were juveniles or sub-adults. Recent surveys in certain parts of the Beni and Santa Cruz lowlands indicate that populations in some areas are still locally abundant. Melanosuchus was found to be relatively abundant within the Beni Biological Station protected area (Pacheco 1993). Densities in six lagoons ranged from 0.47–19.5 individuals/km. Densities of M. niger in rivers were lower (to 1.4/km), but Pacheco considers the Beni Biological Station to harbor an important population of this species. Surveys conducted in rivers in the Rios Blanco y Negro Wildlife Reserve in Santa Cruz have found densities of 1.4/km in the Rio Negro (168km surveyed) and 0.9/km in the Rio Blanco (A. Taber, pers. comm.). Surveys in lakes have not yet been conducted. Reports also suggest the presence of localized populations in floodplain lakes along the Rio Itenez within the Noel Kempff Mercado National Park (D. Rumiz, pers. comm).

Prior to 1979, Bolivian laws permitted the legal cropping of wild Melanosuchus populations (Decreto Supremo 08063 of 1967). Hunting was prohibited between 31 July and 1 January, and the minimum legal size was 2.5m (Medem 1983). Nevertheless these regulations had little effect in controlling the widespread hunting. Presently, the species is fully protected under Decreto Supremo 16606 of 1979 (Klemm and Navid 1989), but some illegal hunting continues (King and Videz-Roca 1989). Pacheco (1990a and b, 1993a and b) presents information on captive breeding and rearing of Melanosuchus in Bolivia.

In August 1990, a total of 25 adult black caiman (>2.2m TL) were released in the Laguna Normandia, located adjacent to the Beni Biological Station near San Borja. These animals came from a group of approximately 150 captive individuals on the El Dorado cattle ranch. They had been brought there in the late 1970s for the establishment of a commercial farm. The release project was sponsored by PRODENA, a Bolivian conservation group, in association with the Beni Biological Station and the owners of El Dorado. Monitoring showed that only a small percentage of these animals remained in the lagoon (Vaca 1992). Pacheco (1995) reports that 8–10 of the group remain resident and reproduction was observed in 1995.

Brazil

Black caiman were at one time found throughout much of the Brazilian Amazon, but today have been extirpated from many of these areas (Plotkin et al. 1983, Brazaitis et al. 1992). Hide hunting was particularly intense in the early 1950s (Fittkau 1973), but was still in evidence in the late 1970s (Magnusson 1979). Magnusson (1979) reported a small population of Melanosuchus in the Tapajos National Park. The largest concentration was in a small lake, Lago das Piranas, where a total of 16 individuals were seen over a distance of 3km. Brazaitis et al. (1988, 1990a and b, 1992) report that the species is seriously depleted throughout central and southern Brazil. Of 47 sites in the Amazon basin, localized populations were only found at six sites: the Río Galera in Mato Grosso, the Río Madeira (Borba) in Amazonas, the Lago Comprido, Pracuba in Amapá, parts of the Rio Branco and Rio Ajarani in Rondonia, the Rio Amazonas at Paraná do Trinidade, Amazonas, and the Rio Uraricoera, Igarapé Grande, in Rondonia.

Magnusson et al. (1994) report a low density of black caiman in the Anavilhanas Archipelago in the Rio Negro, and that some nesting is taking place. Peres and Carkeek (1993) note that although populations of Melanosuchus were intensively hunted in the Brazilian Amazon, and that small-scale hunting for meat continues, populations of both Caiman crocodilus and Melanosuchus niger are recovering in parts of the Amazon and its major tributaries, and illustrates this claim with their experience in the Rio Juruá. In June–July 1994, R. da Silveira (pers. comm.) censused over 700km of rivers, streams and lakes within the nearby Mamirauá Ecological Station. Although these surveys were done during a period of high water, Melanosuchus were observed at low densities at most sites within the reserve. Population surveys by Silveira during lower water periods (October) have demonstrated a healthy population of Melanosuchus, with some densities in excess of 30 individuals/km.

In Brazil, commercial hunting, farming or ranching of the black caiman is prohibited. Illegal hunting continues throughout much of the Amazon. In the Mamirauá Ecological Reserve, dry season hunting for caiman is widespread, with the meat being sold in Leticia (Colombia) or along the lower Amazon (Pará) as pirarucú fish (Arapaima gigas) (da Silveira, pers. comm.). Peres and Carkeek (1993) suggest that this trade is widespread in the Brazilian Amazon. No hide hunting is reported.

Black caiman, Melanosuchus niger, Mamiraua, Brazil, where a substantial population of this
depleted species is reported to be recovering. Photo by J. Thorbjarnarson.

Guyana

Medem (1983) reported that the black caiman was restricted to the upper and middle Essequibo, Rupununi, Rewa, and Berbice Rivers, as well as to two Amazon basin rivers (the Takatu and the Ireng) in Guyana. Gorzula and Woolford (1990) noted a similar distribution but were unable to confirm the reports from the Berbice River. Medem’s survey (1983) found black caiman to be close to extinction in Guyana following a period of intensive hide hunting. During the period of peak hunting, Guyanese residents would apply for permits, then have Brazilian hide dealers from Boa Vista cross the border and organize hunting parties of local Amerindians (Plotkin et al. 1983). Gorzula and Woolford (1990) reported that large-scale commercial hunting took place from 1955 to 1965, and that most of the skins went out via Brazil. Some hunting was reported into the 1970s.

The survey by Gorzula and Woolford (1990) found that Melanosuchus populations had apparently made a recovery in the northern Rupununi region, where they were locally abundant. The overall mean uncorrected population density was 7.4/km (41.2km surveyed). They estimated the total population in the North Rupununi Savanna region to be 2,000–4,000 non-hatchlings. Anecdotal reports suggested that a similar population recovery was taking place downstream to the Tambio Inlet on the Essequibo River.

Following a period of intensive hunting, the Guyanese government initiated a five year ban on caiman hunting in 1968 (Plotkin et al. 1983). As with Caiman, this species was classified as a game animal under the Fisheries Regulations of 1966 (Klemm and Navid 1989). No management program is currently in operation.

French Guiana

In French Guiana, black caiman are found in the coastal Kaw region in the northeast of the country, principally in the seasonally flooded grasslands bordering the Kaw River, and in the neighboring Savanne Angelique swamp. Smaller numbers of black caiman were also reported from the area between the lower Approuague River and the Ounary River located to the east of the Kaw, and in the small Ouapou Creek to the south of the Montagnes de Kaw. Formerly, Melanosuchus was also known from areas to the west of the Kaw including the Gabrielle Creek, and the Mahury River, but has since been extirpated. Along the border with Brazil black caiman were known from the lower Oyapock River and its tributaries, but have been virtually eliminated from this area by Brazilian hunters (Plotkin et al. 1983).

The population in the vicinity of the Kaw was reported to be quite large, but has been severely impacted in recent years by hide hunting (Plotkin et al. 1983). Recent surveys by Behra (1994a) have confirmed the presence of Melanosuchus in the Kaw Swamp and in the Approuague River, but reported that they are absent from the Onanary and Kourouai Rivers. In the Approuague River, the caiman are living in an estuarine environment near islands where freshwater enters the river (Behra 1994a). Most of the animals observed by Behra during a 1993 survey were juveniles, and he suspects that the population increased between 1989 and 1993.

Black caiman were protected in French Guiana in 1968 (Plotkin et al. 1983) but this law apparently did little to stop the commerce in Melanosuchus skins. Stronger legislation was enacted in 1975 which was not immediately effective, but resulted in officials seizing skins and appears to have reduced illegal trade (Plotkin et al. 1983). Black caiman are included in Article 1 of the Decree No. 77- 1295, which provides complete protection throughout the country (Behra, in litt 13 July 1990). This species is also protected in the newly designated Kaw Swamp Sanctuary (Behra 1990). However, Behra (1994a) reports that night time hunting of other crocodilians is allowed, making protection of black caiman difficult.

Black caiman, Melanosuchus niger, Kaw River, French Guiana. Photo by M. Blanc.

Venezuela

Donoso-Barros (1966a, 1996b) reported Melanosuchus in Venezuela, citing a specimen from the Rio Negro originating from the region south of Cocuy. Gorzula and Paolillo (1986) noted the imprecise locality data, and cited Medem (1983) for a lack of confirmed specimens from Venezuela. Based on their observations in Bolivar and Amazonas states they concluded that no firm evidence suggested Melanosuchus to be found within Venezuela. King (1991) reported a black caiman killed just southeast of Puerto Ayacucho (presumably in or around the Rio Cataniapo) in 1967 by Jay Wilson, a caiman hide dealer. King (1991) suggests that this area and other sites in the upper Orinoco be revisited to confirm this record.

Priority projects

High priority

Population Status Surveys: The lack of population status information throughout the species’ range is a major limiting factor for the development of conservation and management programs for this species. Countries such as Colombia are interested in developing management programs based on controlled commercial utilization, once adequate information has been obtained on the species status in that country. Very little information is available from throughout most of Brazil, Bolivia, French Guiana (particularly the Kaw Swamp), and Peru. There is anecdotal evidence that population recovery is taking place in certain areas, and this needs to be documented through systematic survey work. Historically, Marajo island at the mouth of the Amazon held huge populations of black caiman which were killed off by ranchers. Recent reports of a recovering population should be investigated. In Ecuador, basic surveys have been carried out, but need to be continued in the form of population monitoring as part of the ranching program.

Basic Ecological Studies: Although it has a wide distribution and in some areas is found in locally dense populations, few ecological studies have been conducted on Melanosuchus. Certainly, in comparison to Caiman crocodilus, very little is known about black caiman. Ecological investigations now underway in Brazil at the Mamirauá Ecological Station should be continued and expanded. Ecological studies should be incorporated into the ranching and population monitoring program in Ecuador.

Initiate management programs in Brazil: Brazaitis et al. (1988) strongly urged the development of a coordinated management program for black caiman and the other crocodilians in Brazil. This program should include long-term ecological investigations in areas such as the Río Guapore (near Guajara Mirim and Costa Marques) and the Río Galera in Mato Grosso. Several sites in Amazonas state, particularly the Mamirauá Ecological Reserve, are good candidates as well.

Regional management coordination: Coordinated efforts between the range states of this species to develop compatible sustainable use programs and to control illicit trade are needed. Efforts need to be directed at controlling the illegal sale of caiman meat (including international control of the trade in meat between Brazil, Colombia, and Peru, particularly in Leticia) as a first step towards evaluating the potential for controlled commercial management. Initiatives to achieve this are underway under the auspices of the Amazonian Treaty and under the leadership and coordination of Colombia.