Black Caiman

## Description

The black caiman (Melanosuchus niger ) is a species of large crocodilian and, along with the American alligator, is one of the largest extant members of the family Alligatoridae and order Crocodilia. It is a carnivorous reptile that lives along slow-moving rivers, lakes, seasonally flooded savannas of the Amazon basin, and in other freshwater habitats of South America. It is a large species, growing to at least 5 m (16 ft) and possibly up to 6 m (20 ft) in length, which makes it the third largest reptile in the Neotropical realm, behind the American crocodile, and the Orinoco crocodile. As its common and scientific names imply, the black caiman has a dark coloration as an adult. In some individuals, the dark coloration can appear almost black. It has grey to brown banding on the lower jaw. Juveniles have a more vibrant coloration compared to adults with prominent white to pale yellow banding on the flanks that remains present well into adulthood, at least more when compared to other species. 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 crocodile-like animals, 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 bodies are underwater.

The black caiman is the largest predator in the Amazon ecosystem, preying on a variety of fish, reptiles, birds, and mammals. It is a generalist and apex predator, potentially capable of taking any animal within its range, including other predators. Few ecological studies have been carried out on the species, but the black caiman has its own ecological niche that enables coexistence without too much competition. As the largest predator in the ecosystem, it may also be a keystone species, playing an important role of maintaining the structure of the ecosystem. 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. It is a dangerous species to humans, and attacks have occurred in the past.

## Appearance

The Black caiman is the biggest of all species of alligator, some reaching six meters long. This impressive aquatic predator is the largest animal in the Amazon Basin. Superficially it looks like the American alligator, and its protective armored skin, as its name suggests, is dark in color. This skin color helps to camouflage it during its nocturnal hunts, and may also help to absorb heat. The lower jaw has bands of grey (brown in older animals) with white or pale yellow bands across their flanks. The banding fades gradually as the animal gets older.

## Distribution

These aquatic reptiles inhabit much of the area of the Amazon Basin, including much of both northern and central South America (Bolivia; Brazil; Colombia; Ecuador; French Guiana; Guyana; Peru). They occur in shallow, freshwater bodies of water like slow-moving streams, rivers, and lakes, and sometimes in flooded savannah and wetlands.

## Behavior

From May until July there is a period of flooding throughout the Amazon, and at this time Black caimans are dispersed throughout their range. From September through December is the dry season, when water levels recede, savannahs that were flooded dry up, and these alligators are more densely gathered in the permanent rivers and lakes. They usually hunt during the night, using their sensitive sight and hearing to catch birds, fish, turtles, capybaras, and some larger mammals. They have teeth that are made to grasp their food, but not chew or kill it, so they normally drown their catch, and, if it is of a small enough size, swallow it whole. They leave larger prey to rot, and, when decayed enough, they eat it. Black caimans make noises like rumbling thunder for communication with their own species.

## Diet

Black caimans are carnivores. Fish are the major part of this animal’s diet, especially catfish and the dangerous piranha, but adults also go after much larger prey like capybara, turtles, deer, cats, and dogs. Juveniles eat smaller foods, including crustaceans, snails and other invertebrates, and fish.

## Reproduction

Little is known about the mating system of the Black caiman. Generally, crocodilians exhibit polygynous behavior, when males mate with more than one female during the breeding season. It is thought that female Black caimans nest from September to December, during the dry season, when water levels drop and fish have only shallow pools to swim in, providing an easy and abundant meal. These animals use plant material to build a nest mound measuring around 1.5 meters across, where a large clutch of as many as 65 eggs are laid. Females remain close to their nests, waiting 42 to 90 days for the eggs to begin to hatch, and they open the nest to help with the hatching process. Often many females next close together, so large numbers of hatchlings emerge at the same time at the start of the wet season, thus gaining safety in numbers. A mother will try to care for her young for a few months but they are largely independent. Most do not make it to adulthood. Female Black caimans breed only once in 2 to 3 years.

## Population

### Population threats

For many years, this species was hunted heavily for its tough skin, to make shiny, black leather. Over the last century, this extreme hunting pressure reduced the overall population by 99 percent, and it is now almost extinct in some places, such as Colombia, as well as the Amazon River itself. Populations continue to be impacted by illegal hunting, as well as habitat destruction through deforestation swamplands being burnt. Competition with the more common spectacled caiman may also threaten Black caiman populations.

### Population number

According to the Animal Corner resource, the total population size of the Black caiman is around 25,000-50,000 individuals. According to the Crocodilian resource, the total population size of this species is up to 1,000,000 individuals. Overall, currently, Black caimans are classified as Least Concern (LC) on the IUCN Red List.

### Ecological niche

Being the largest predator in the Amazon ecosystem, the Black caiman may play the role of a keystone species and help to maintain the structure of its ecosystem. Important activities may include nutrient cycling and the selective predation of certain fish species.

## Fun Facts for Kids

Caimans make use of their flattened tails for both swimming and to protect against predators.

Caimans have very good hearing and eyesight.

Caimans play an important role in their native habitats, as they keep numbers of their prey under control. The reduction of caimans in the wild meant an increase in the number of piranhas (which attack cattle) and capybaras (which destroy crops).

Caimans like to bask in the sun and on the shore and cool off by sinking down into cold water.

Black caimans are unique among crocodilians due to much of the juvenile coloration - yellowish stripes and spots - being retained well into adulthood. These relatively vibrant colors have caused a considerable threat to this species, their hide being highly prized for the skin trade.

Stories about Black caimans hunting humans heavily are fiction. They will attack people if they approach too closely and the animal feels threatened.