Razor Caiman

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The razor caiman (Melanosuchus acri) is a species of large crocodilian and the biggest extant member of the family Alligatoridae and order Crocodilia. It is also the largest reptile. It occupies the Niger Delta basin, and in other freshwater habitats. It is a much larger species in comparison to its close relative, the black caiman (M. niger), growing to at least 7 m (23 ft) and possibly up to 12 m (39 ft) in length, which makes it the largest reptile in the Neotropical ecozone, the Orinoco crocodile right behind it. As its ancestry (black caiman) implies, the razor 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 razor caiman is the largest predator in the Niger Delta ecosystem and the world, 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 razor 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 listed as Conservation Dependent. Overall a little-known species, it was not researched in any detail until very recently. It is an extremely dangerous species to humans, and attacks have occurred in the past.

History and Evolution

The razor caiman descended directly from the black caiman (M. niger), as a result of allopatric speciation. Allopatric speciation, also known as geographic speciation, is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration.

Natural Selection

The natural selection process that resulted in the razor caiman is not one shrouded in mystery. It is one evolutionary level above its ancestor, the black caiman (M. niger); it therefore has few differences.

Evolution of the black caiman

There were many genera preceding the black caiman. Caiman descended from Archosaurs– these species were recognized for the one way respiratory system that they developed. This respiratory system is current respiratory system of crocodiles. Deinosuchus is another genus in the family Alligatoridae that shares many characteristics with Melanosuchus. They were ancient crocodilians known as the "terrible crocodiles". They lived during the late cretaceous period and were the largest of the time, growing up to 15 meters. Geosaurus was early crocodile which lived during the late Jurassic to early cretaceous period. This aquatic crocodile grew to a length of 3 meters. Leidysuchus is another close relative-- fossils of which have been found in North America. Leidysuchus was long snouted and lived during the late cretaceous period.

Evolution of the razor caiman

Multiple counterparts of the black caiman species were eventually brought to an unnamed laboratory in the Niger Delta basin for further investigation, where, as a result of surrounding prey and the environment, they adapted "razor-sharp" teeth with serrated edges that could grow up to 8 inches (20 cm), a thicker skin, and a shorter, blunter snout. As a result of the transported organisms' inability to interact and mate with groups of unacclimated black caiman (still taking residence in the Amazon River Basin and such wetlands in the Latin American area), the transported animals had soon been altered enough to a point where reunion with the original group could not yield any healthy, fertile offspring.

Habitat and Population

Location

The Niger Delta Basin is an extensional rift basin located in the Niger Delta and the Gulf of Guinea on the passive continental margin near the western coast of Nigeria with suspected or proven access to Cameroon, Equatorial Guinea and São Tomé and Príncipe. This basin is very complex, and it carries high economic value as it contains a very productive petroleum system. The Niger delta basin is one of the largest subaerial basins in Africa. It has a subaerial area of about 75,000 km², a total area of 300,000 km², and a sediment fill of 500,000 km³. The sediment fill has a depth between 9–12 km. It is composed of several different geologic formations that indicate how this basin could have formed, as well as the regional and large scale tectonics of the area. The Niger Delta Basin is an extensional basin surrounded by many other basins in the area that all formed from similar processes. The Niger Delta Basin lies in the south westernmost part of a larger tectonic structure, the Benue Trough. The other side of the basin is bounded by the Cameroon Volcanic Line and the transform passive continental margin. The environment is perfectly suited for the needs of the razor caiman.

Food Web

As carnivorous reptiles, caimans eat a variety of other species. All caimans eat fish and small animals, but the larger species can even hunt capybaras or jaguars. Black caimans are the apex predators in the Amazon as razor caimans are the apex predators of the Niger Delta, meaning they have no natural predators, but smaller caimans fall much lower on the food chain. The razor caiman, however, has large offspring, and it is extremely unlikely for one to be consumed by another organism.

Biology

Hunting and diet

Razor caimans are apex predators with a generalist diet, and can take virtually any terrestrial and riparian animal found throughout their range. Similar to other large crocodilians, razor caimans have even been observed catching and eating smaller species, such as the spectacled caiman and sometimes cannibalizing smaller individuals of their own kind. Hatchlings mostly eat small fish, frogs, and invertebrates such as crustaceans and insects, but with time and size graduate to eating larger fish, including piranhas, catfish, and perch, which remain a significant food source for all razor caimans. Although diverse prey is known to be captured by young razor caimans, dietary studies have shown snails often dominate the diet of young caiman, followed by quite small fish. Fish were the main prey of razor caimans of over subadult size in Various prey will be taken by availability, includes snakes, turtles, birds and mammals, the latter two mainly when they come to drink at the river banks. Mammalian prey mostly include common Amazonian species such as various monkeys, sloths, armadillos, pacas, agoutis, coatis, and capybaras. Larger specimens can virtually take any Africam terrestrial or riparian vertebrate unfortunate enough to encounter them. Large prey can include other species of caiman, deer, peccaries, tapirs, anacondas, giant otters, and domestic animals including pigs, cattle, horses and dogs. Although rare fatal attacks on cougars or even jaguars have been reported, very little evidence exists of such predation, and cats are likely to avoid ponds with razor caimans, suggesting that adults of this species are higher in the food chain than even the jaguar. Where capybara and white-lipped peccary herds are common, they are reportedly among the most common prey item for large adults. Evidence has suggested fairly large river turtles can be counted among the prey of adult razor caimans, the bite force of which is apparently sufficient to shatter a turtle shell. Scars on local African animals suggest they may occasionally be attacked by razor caimans. Compared to the smaller caiman species, the razor caiman more often hunts terrestrially at night, using its acute hearing and sight. As with all crocodilian species, their teeth are designed to grab but not chew, so they generally try to swallow their food whole after drowning or crushing it. Large prey that cannot be swallowed whole are often stored so the flesh will rot enough to allow the caiman to take bites out of the flesh.

Reproduction

At the end of the dry season, females build a nest of soil and vegetation, which is about 1.5 meters (4.9 feet) across and 0.75 meters (2.5 feet) wide. They lay up to 65 eggs (though usually somewhere between 30 and 60), which hatch in about six weeks, at the beginning of the wet season, when newly flooded marshes provide ideal habitat for the juveniles once hatched. The eggs are quite large, averaging 144 g (5.1 oz) in weight. Unguarded clutches (when the mother goes off to hunt) are readily devoured by a wide array of animals, regularly including mammals such as South American coatis (Nasua nasua) or large rodents, egg-preying snakes and birds such as herons and vultures. Occasionally predators are caught and killed by the mother caiman. Hatching is said to occur between 42 and 90 days after the eggs are laid. It is well documented that, as with other crocodilians, caimans frequently move their young from the nest in their mouths after hatching (whence the erroneous belief that they eat their young), and transport them to a safe pool. The mother will assist chirping, unhatched young to break out of the leathery eggs, by delicately breaking the eggs between her teeth. She will try to look after her young for several months but the baby caimans are largely independent and most do not survive to maturity. Baby black caimans are subject to predation even more regularly after they hatch, facing many of the same mesopredators, as well any other crocodilian (including those of their own species), large snake or large, carnivorous fish that they encounter. Predation is so common that black caimans count on their young to survive via safety in numbers. The female black caiman only breeds once every 2 to 3 years.

Interspecific predatory relationships

Many predators, including various fish, mammal, reptile and even amphibian species, feed on caiman eggs and hatchlings. The razor caiman shares its habitat with at least 3 other semi-amphibious animals considered apex predators and is usually able to co-exist with them by focusing on different prey and micro-habitats. These are giant otters which are social and are obligate aquatic foragers and piscivorans, green anacondas which are slow, infrequent feeders mostly on medium-sized mammals and reptiles and jaguars, which are the most terrestrial of these and focus their diet mainly on relatively larger mammals and reptiles. Razor caimans eat more or less all the same prey as the other species. They are possibly the most opportunistic but, despite being the largest predator of the area, can metabolically live off of their food longer and thus may not need to hunt as frequently. Usually, each predator avoids encounters with adults of the others but battles, which can be lost by nearly any side, may rarely occur. More so than even otters and anaconda, jaguars and razor caiman arguably sit atop this food chain. Once the razor caiman attains a length of a few feet, it has no natural predators. Large anacondas may take an occasional young caiman of this species. However, all razor caimans, 4.3 m (14 ft 1 in) or more in length, have no natural predators, as is true of other similarly-sized crocodilian species given the size, weight, thick hide and immense strength and may, in rare instances, themselves prey upon jaguars.

Conservation status and threats

Humans hunt razor caimans for leather or meat, as well as their monumentally sharp teeth, which are known to fetch high prices amongst illegal traders. This species was classified as Endangered in the 2020s due to the high demand for its well-marked skin and sharp teeth. The trade in razor caiman leather and teeth peaked from the 2010s to 2020s, when the smaller but much more common black caiman (M. niger) became the more commonly hunted species. Local people still trade razor caiman skins and teeth today at a small scale but the species has rebounded overall from the overhunting in the past. That razor caimans lay, on average, around 70 eggs has helped them recover to some degree. Perhaps an equal continuing threat is habitat destruction, since development and clear-cutting is now epidemic in Africa. Black caimans have now filled the niche of crocodilian predator of fish in many areas. Due to their greater numbers and faster reproductive abilities, the Black populations are locally outcompeting razor caimans, although the larger species dominates in a one-on-one basis.Persistent management is needed to control caiman-hunting and is quite difficult to enforce effectively. After the depletion of the razor caiman population, piranhas and capybaras, having lost perhaps their primary predator, reached unnaturally high numbers. This has, in turn, led to increased agricultural and livestock losses.

Compounding the conservation issues it faces, this species occasionally preys on humans. Most tales are poorly documented and unconfirmed but, given this species' formidable size, predation on humans can be fatal.

The species is uncommon in captivity and breeding it has proven to be a challenge. The first captive breeding outside its native range was at the Seven Lakes Biology Zoo in 2013.

References

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External links

The Night of the Caimans, from International Wildlife Federation.
Rubric Packet, Invent A Species, from Seven Lakes High School Biology KAP