The black caiman (Melanosuchus niger) is a crocodilian reptile endemic to South America. With a maximum length of around and a mass of over , it is the largest living species of the family Alligatoridae, and the third-largest crocodilian in the Neotropical realm.Black Caiman (Melanosuchus niger). Crocodilian Specialist Group. Retrieved on 2013-04-13.Melanosuchus niger Black caiman. Animal Diversity Web. Retrieved on 2013-04-13.Black Caiman (Melanosuchus niger). Crocodile Specialist Group. True to its common and scientific names, the black caiman has a dark greenish-black coloration as an adult. In some individuals, the pigmentation can appear almost jet-black. It has grey to brown banding on the lower jaw; juveniles have a more vibrant coloration compared to adults, with prominent white-pale yellow banding on the flanks that remains present well into adulthood (more than most other species). The banding on young helps with camouflage by breaking up their body outline, on land or in water, in an effort to avoid predation. The morphology is quite different from other caimans but the bony ridge that occurs in other caimans is present. The head is large and heavy, an advantage in catching larger prey. Like all crocodilians, caimans are long, squat creatures, with big jaws, long tails and short legs. They have thick, scaled skin, and their eyes and noses are located on the tops of their heads. This enables them to see and breathe while the rest of their body is underwater.

A carnivorous animal, the black caiman lives along freshwater habitats, including slow-moving rivers, lakes and seasonally flooded savannas, where it preys upon a variety of fish, reptiles, birds, and mammals. Being an apex predator and potentially a keystone species, it is a generalist, capable of taking most animals within its range, and might have played a critical role in maintaining the structure of the ecosystem.Black Caiman, Black Caiman Skull. Dinosaurcorporation.com. Retrieved on 2012-08-23. Although only a mere few specific ecological studies have been conducted, it is observed that this species has its own niche which allows coexistence with other competitors.

Reproduction takes place in the dry season. Females build a nest mound with an egg chamber, protecting the eggs from predators. Hatchlings form groups called pods, guarded by the presence of the female. These pods may contain individuals from other nests. Once common, it was hunted to near extinction primarily for its commercially valuable hide. It is now making a comeback, listed as Conservation Dependent. Overall a little-known species, it was not researched in any detail until the 1980s, when the leather-trade had already taken its toll.Crocodilian Species – Black Caiman (Melanosuchus niger) . Crocodilian.com. Retrieved on 2012-08-23. It is a dangerous species to humans, and attacks have occurred in the past.

Classification Although the black caiman is the sole extant (living) species of the genus Melanosuchus, two fossil species found in South America have been described: Melanosuchus fisheri in 1976, and Melanosuchus latrubessei in 2020, although the status of M. fisheri is in doubt. The black caiman is a member of the caiman subfamily Caimaninae, and is one of six living species of caiman. It is most closely related to the caimans of the genus Caiman, as shown in the cladogram below, based on molecular DNA-based phylogenetic studies:

Distribution The black caiman largely inhabits areas of Amazonia, living in rivers, swamps, wetlands, and lakes. It is found in Brazil, eastern Ecuador and Peru, northern Bolivia, eastern French Guiana, and southern Guyana.Thorbjarnarson JB (2010). Black Caiman Melanosuchus niger. Crocodiles. Status Survey and Conservation Action Plan. Third Edition. 29-39.

Characteristics

The black caiman has dark-coloured, scaly skin. The skin coloration helps with camouflage during its nocturnal hunts, but may also help absorb heat (see thermoregulation). The lower jaw has grey banding (brown in older animals), and pale yellow or white bands are present across the flanks of the body, although these are much more prominent in juveniles. This banding fades only gradually as the animal matures. The bony ridge extending from above the eyes down the snout, as seen in other caiman, is present. The eyes are large, as befits its largely nocturnal activity, and brown in colour. Mothers on guard near their nests are tormented by blood-sucking flies that gather around their vulnerable eyes, leaving them bloodshot.

The black caiman is structurally dissimilar to other caiman species, particularly in the shape of the skull. Compared to other caimans, it has distinctly larger eyes. The snout is relatively deep, and the skull (given the species' considerably larger size) is much larger overall than other caimans. Black caimans are relatively more robust than other crocodilians of comparable length. There appears to be varying skull morphology in this species depending on the age and particular individual animal, which is not uncommon in other modern crocodilians, and by gender, with adult males typically having much more massive skulls relative to their size than like-age females. Due to the differences, males have a stronger bite force and likely exploit a different, and larger, prey base than females.Foth, C., Bona, P., & Desojo, J. B. (2015). Intraspecific variation in the skull morphology of the black caiman Melanosuchus niger (Alligatoridae, Caimaninae). Acta Zoologica, 96(1), 1-13. Young black caimans can be distinguished from large spectacled caimans by their proportionately larger head, as well as by the colour of the jaw, which is light coloured in the spectacled caiman and dark with three black spots in the black caiman. A , black caiman was found to have a bite force of .

Size

The black caiman is the largest predator in the Amazon basin and the largest member of the Alligatoridae family, making it one of the largest extant reptiles. It is also significantly larger than other caiman species. Most adult black caimans are in length, with a few old males exceeding . Sub-adult male specimens of around will weigh roughly , around the same size as a mature female, but will quickly increase in bulk and weight. The average size of adult females at their nests was found to be .Thorbjarnarson JB (2010). "Black Caiman Melanosuchus niger ". pp. 29–39. In: Manolis SC, Stevenson C (editors). Crocodiles. Status Survey and Conservation Action Plan. Third edition. Darwin: Crocodile Specialist Group. iucncsg.org Mid-sized mature males of weigh approximately , while large mature specimens exceed , being relatively bulky crocodilians.French Guiana . kwata.net (2003).Da Silveira, R., Do Amaral, J.V., Mangusson, W.E. & Thorbjarnarson, J.B. (2011). Melanosuchus niger: Signaling Behavior & Long-Distance Movement. Herpetological Review, 42 (3): 424-425.Sirder, H. (2014). Le Caiman noir, Espèce transamazonienne. Livret édité par le Parc naturel régional de la Guyane dans le cadre du programme OYAN, Parque nacional Cabo Orange. Very large, old males can exceed in length, and weigh up to . A relatively small adult male of a total length of weighed while an adult male considered fairly large at a length of weighed approximately . Another sampling of sub-adult males found them to range in length from , averaging , and that they weighed from , averaging . In a study conducted in Rupununi River, Guyana, sub-adult and adult black caimans ranged from in length and weighed between . In some areas (such as the Araguaia River) this species is consistently reported at in length, although specimens this size are uncommon. Several widely reported but unconfirmed (and probably largely anecdotal) reports claim that the black caiman can grow to over in length and weigh up to .Johnson, C., Anderson, S., Dallimore, J., Winser, S., & Warrell, D. A. (2008). Oxford handbook of expedition and wilderness medicine. OUP Oxford. While it is unclear what the sources for this maximum size are, many scientific papers accept that this species can attain extreme sizes as such.Da Silveira, R., Magnusson, W. E., & Campos, Z. (1997). Monitoring the distribution, abundance and breeding areas of Caiman crocodilus crocodilus and Melanosuchus niger in the Anavilhanas Archipelago, Central Amazonia, Brazil. Journal of Herpetology, 514-520.Barker, G. M. (Ed.). (2004). Natural enemies of terrestrial molluscs. CABI.Junk, W. J., & da Silva, V. M. F. (1997). Mammals, reptiles and amphibians. In The Central Amazon Floodplain (pp. 409-417). Springer, Berlin, Heidelberg. In South America, two other crocodilians reportedly reach similar sizes: the American crocodile (Crocodylus acutus) and the Orinoco crocodile (C. intermedius).

Biology and behaviour

Hunting and diet