Numbered among the neotropical fauna are nine species of crocodiles or caimans. Once abundant in the rivers, lagoons and swamps of tropical America, the extensive commercial hunting for their hides that began in the 1920s or 30s has now relegated them to islands of residual populations (see 2.4.2.1).
Most of the prized crocodilians are endangered species (Table 23) in urgent need of protection and recovery measures such as strictly protected areas or captive breeding. Among the less persecuted species, dwarf caiman (Paleosuchus) are fairly important in indigenous subsistence hunting, but their low numbers, small size and heavily ossified skins render them of little commercial value.
The spectacled caiman (Caiman crocodilus), also known as C. sclerops (16, 377), is the only species now locally abundant, of some commercial value, and conceivably an exploitable resource in specific regions.
Local names: Alligator (Guyana, Trinidad), baba (Venezuela), babilla (Colombia), yacaré, yacaré tinga (Brazil), Kaaiman (Suriname), lagarto, lagarto chato (Mexico, Central America), lagarto blanco (Ecuador, Peru), yacaré cascarudo (Argentina), yacaré jhu (Paraguay).
Geographical variation and distribution: This is the most widely distributed American crocodilian, ranging from Mexico to Argentina. Brazaitis (77) recognizes four subspecies: Caiman crocodilus fuscus from Oaxaca on the Pacific coast of Mexico down through Central America to northern Colombia and the Maracaibo basin in Venezuela; C. c. crocodilus found in the Orinoco river basin, Amazonia, the Guianas and the island of Trinidad; C. c. apaporensis, only on the Apaporis river in southeastern Colombia, and C. c. yacare (103, 141, 377) in southern Brazil including the Mato Grosso, Bolivia, Paraguay and northern Argentina.
Elevational range: C. crocodilus is restricted to the tropical lowlands; the limits of its range coinciding with the annual isotherm of 24°C (118). The highest reported sighting was at 800 m in Colombia (377).
Size and weight: The spectacled caiman varies by size and weight according to sex, age and locality. The total maximum length reported by Medem (377) was 240 cm for males and 173 cm for females, with maximum weights of 45 kg for males and 19 kg for females. Maximum sizes and weights reported for males in the Venezuelan llanos were 231 cm and 58 kg, and for females 161 cm and 20 kg (31). Most adults grow to 120-200 cm, and weigh 7-40 kg. Mexican spectacled caiman, sometimes referred to as C. crocodilus chiapasicus, may be smaller (16) compared to C. crocodilus yacare, which can reach 250 cm and weigh 58 kg (males). Adult females can weigh up to 14-23 kg (140).
Habitat: C. crocodilus can be found in a variety of habitats from rivers, creeks, lagunas and estuaries in forest or savannah areas to bogs and brackish mangrove swamps in coastal areas (16, 31, 377, 531, 599). They prefer calm, often turbid waters, with floating or emerging vegetation. Most habitats have marked seasonal flooding and dry periods, the animals congregating in the remaining bodies of water during the dry season. Which part of the habitat caiman use and when depends on their age and sex (31, 531).
Table 23. Synoptic table of Latin American Crocodilia; sources of information: 16, 31, 77, 103, 377, 378
|
Species |
Local name |
Total length (cm) maximum length in parentheses |
Geographical distribution |
Commercial value |
IUCN status (246) |
|
Caiman crocodilus |
baba, babilla |
150-200 (250) |
From Oaxaca, Mexico through Central America and south to the River Paraguay and Argentina |
medium |
vulnerable |
|
Caiman latirostris |
jacare de papo |
200-250 (300) |
Western Brazil from Rio Grande do Norte to northern Uruguay |
high |
endangered |
|
Melanosuchus niger |
jacare acu |
300-400 (500) |
Amazon River basin in Brazil, Bolivia, Guyana, Colombia and Peru |
high |
endangered |
|
Paleosuchus palpebrosus |
jacare coroa |
90-120 (200) |
From southern Colombia through Venezuela Guyana and to southern Brazil |
low |
|
|
Paleosuchus trigonatus |
jacre coroa |
100-130 (226) |
From southern Colombia and Venezuela to Bahía, Brazil, Peru and the Bolivian Amazon |
low |
|
|
Crocodylus acutus |
cocodrilo de río |
300-400 (700) |
Pacific slope from Nayarit, Mexico to Torbes, Peru. Atlantic slope from Florida to Venezuela |
high |
endangered |
|
Crocodylus intermedius |
caimán llanero, |
400-450 (678) |
Orinoco River basin in Colombia and Venezuela |
high |
endangered |
|
Crocodylus moreletii |
cocodrilo de pantano |
100-150 (250) |
Atlantic slope from Tamaulipas, Mexico to Guatemala and Honduras |
high |
endangered |
|
Crocodylus rhombifer |
cocodrilo perla |
200-250 (350) |
Cuba |
high |
endangered |
Abundance: The easiest way to estimate spectacled caiman population density is by night counts during the dry season ((31, 530, 531). The average variation in population densities (No./ha of water surface) on 19 farms in the Venezuelan llanos ranged from 57 to 1 119, and crude density (No./ha of farm area) from 0.07 to 15.4 (31, 530, 562). These figures are exclusive of animals under the age of one and most represent population saturation. Vásquez (599) cites specific population densities of 0.77-8.22/ha in the Peruvian Amazon.
Behaviour: The spectacled caiman, like other crocodilians, is mainly static, preferring to remain immobile and partially submerged, or to bask on the shores, particularly in mid-morning and early afternoon (except on overcast days) (31, 530). Despite the animal's apparent immobility, situations calling for a fight/flight response or the presence of potential prey can elicit very rapid and agile movement. Spectacled caiman feed in the water at any time, but mainly at night (16, 377). Adult males turn aggressive and, apparently, territorial at the onset of the rainy season and of heat. They are fairly unsuspicious in quiet habitats but timid where they have been hunted (377, 387). They have 13 visual and nine voiced patterns (31).
Feeding habits: Neonates feed on aquatic and terrestrial insects, expanding to include crustaceans, molluscs and fish as they grow. The basic adult diet varies from place to place, and includes fish (478, 562) and crustaceans (16, 599), or a combination of molluscs, crustaceans and fish (31, 377). Full-sized adults also prey on mammals, semi-aquatic or aquatic reptiles, and birds. They also eat carrion.
Reproduction: C. crocodilus takes at least six years to reach sexual maturity, corresponding to an approximate overall length of 114 cm (approximately 60 cm snout/vent) (242). Courtship and mating coincide with the onset of the rains. The female then builds her nest - a mound of earth and plant matter, some 40 cm high and at least 1 m in diameter - on a site near water but not subject to flooding, often building over an earlier nest (31, 140). She lays a clutch of eggs, usually at peak flooding, which is July-August in the llanos (377, 562) and January-February in the Colombian Amazon (377) and the Pantanal de Mato Grosso (140), although this is apparently not the definitive pattern for all sites (377, 599).
The number of eggs ranges from 12 to 44 with a mean clutch size of 29, depending on female body size (497). During the 65-84 day incubation period (various authors), the female guards the nest. The hatchlings emerge with the oncoming dry season, measuring 20-23 cm in length (16, 140, 503, 562), and the mother remains with them during the first few months of life.
Mortality: Despite maternal care, there is nest depredation by coatis (140), Tegu lizards (148, 562) and other animals, and some nests are destroyed by flooding, trampling or human interference (egg collecting). A bare 20-25 percent of the eggs hatch successfully (31, 140, 148, 562 and 563). Hatchling predators include wader birds, raptors and other carnivores, and almost all die before the age of one year. Adult mortality, on the other hand, is thought to be extremely low (31, 148).
Hunting: Spectacled caiman are usually hunted at night from canoes, as the hunters can get much closer than in the daytime and can easily find the animals by their eyes which shine red in the torch beam. Rivero Blanco (468) reports on the principal technique in the Venezuelan llanos: by day the animals are herded into a section of the lagoon where they can be easily captured. Animals of legal size are then harpooned, pulled ashore with ropes and finished off with clubs. They are easier to catch in the dry season when the waters have receded.
They are hunted with harpoons, rifles or shotguns. The traditional harpoon with a wooden handle and detachable head attached to a strong rope that comes off in the prey requires more skill and less distance on the part of the hunter, but it does avoid the loss of wounded animals that is so frequent when caiman are hunted with guns (377). Meat-baited hooks with a wire and wood floater are also used (188, 599), and sometimes trawlnets or traps.
Products: Some indigenous people (Table 6) (and campesinos to a lesser extent) hunt caiman for its tasty but rather tough white meat, and they may sell it as salted and dried slabs (like fish). It is recommended that animals hunted for their skins also be eaten to increase the nutritional and economic contribution of the species (498). Fresh caiman eggs are a preferred food in the llanos region.
Commercial hunting for spectacled caiman skins began on an intensive scale in the 1950s (see 2.4.2). This is currently the only crocodilian that can be harvested in tropical America. To remove the skin the animal is split down the back with a machete or chainsaw so as to preserve the flanks and belly. With medium-sized animals measuring 3-5 feet (91-152 cm), the entire body is used ("coverall" or mantle type). Only the soft leather of the flanks from the throat to the vent (jacket or belt type) is used in the case of the highly ossified big males. The hide is preserved salted and semi-dried and the meat is usually discarded. The commercial value of a legal-size, raw caiman hide at producer level in Venezuela in 1988 was approximately US$50. These prices make caiman harvesting very profitable. Desiccated hatchlings and young are often sold as tourist souvenirs.
Management: The establishment of minimum harvest sizes of 120 and 150 cm in Colombia (118), 200 or 150 cm in Peru (281) and 180 cm in Venezuela (603), plus bag limits per hunter (to a lesser extent), have all been used to regulate caiman hunting. Hunters, traders and tanners have all eluded both size and bag limits for lack of supervision, and so most countries in the area have opted for a total ban as an emergency measure. Both indiscriminate slaughter and blanket prohibitions minimize the potential contribution of the species as an exploitable resource. The planning and implementation of rational management and harvesting based on C. crocodilus biology are urgently needed.
The features of spectacled caiman life history, as for the other major reptiles, are high reproductive capacity, high mortality at the egg and neonate stage, a long preamble to sexual maturity and low adult mortality. This latter attribute has helped to maintain large stable populations which can partially occupy the niche left vacant by Crocodylus (188, 377, 531). Commercial exploitation of adult caiman has had a very destructive impact on population due to the low capacity for recovery. The impact of density/dependence on population dynamics and growth, as well as the net production rate at whatever density, are apparently unknown.
An experimental harvesting programme using wild populations in private farms was recently launched in Venezuela. The population size was first estimated and low harvest rates allowed (7 percent of the population aged one year or over) (Table 17). Complementary and/or alternate measures were 1) the protection of nesting sites; 2) artificial incubation of egg clutches and the captive breeding of hatchlings up to the age of one year followed by release into the wild, and 3) captive breeding up to the age of three years (1 metre total length), slaughter and sale (148, 603). Given the economic importance of the species in Venezuela, both rural producers and reptile leather tanners set up associations in 1987 to promote research, production and sustained utilization, which augurs well for C. crocodilus management.
Captive breeding: As a means of combating egg and hatchling depredation, experiments have been carried out with artificial incubation using polyethylene shelters, wooden crates and polyethylene bags as nests, as well as breeding hatchlings in tanks or cages (60, 497, 503). The mean growth of hatchlings fed a variety of diets of animal origin ranged from 1.5 cm (503) to 2.5 cm (497) per month (the individual monthly maxima were 3 cm and 29 g). When group size per tank was increased from 15 to 35, mean growth dropped and individual variations increased. A number of privately owned captive breeding establishments have recently been set up in Venezuela, providing a growing backlog of experience on the maintenance of this species in captivity.
