Black caiman

A swimming black caiman.

The black caiman is one of the largest extant reptiles. It is the largest predator in the Amazon basin, and also potentially the largest member of the family Alligatoridae. It is also significantly larger than other caiman species. Most adult black caimans are 2.2 to 4.3 m (7 ft 3 in to 14 ft 1 in) in length, with a few old males exceeding 5 m (16 ft 5 in). Sub-adult male specimens of around 2.5–3.4 m (8 ft 2 in – 11 ft 2 in) will weigh roughly 95–125 kg (209–276 lb), 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 2.8 m (9 ft 2 in).[13] Mid-sized mature males of 3.5–4 m (11 ft 6 in – 13 ft 1 in) weigh approximately 300 kg (660 lb), while larger male specimens reach weights of more than 400 kg (880 lb), possibly up to 600 kg (1,300 lb), being relatively bulky crocodilians.[14][15][16] A relatively small adult male of a total length of 3.4 m (11 ft 2 in) weighed 98 kg (216 lb) while an adult male considered fairly large at a length of 4.2 m (13 ft 9 in) weighed approximately 350 kg (770 lb).[15][17] Another sampling of subadult males found them to range in length from 2.1 to 2.8 m (6 ft 11 in to 9 ft 2 in), averaging 2.45 m (8 ft 0 in), and that they weighed from 26 to 86 kg (57 to 190 lb), averaging 48 kg (106 lb).[18] In some areas (such as the Araguaia River) this species is consistently reported at 4 to 5 m (13 ft 1 in – 16 ft 5 in) 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 6.1 m (20 ft 0 in) in length and weigh up to 1,100 kg (2,400 lb).[9][10][19] 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.[20][21][22] In South America, two other crocodilians reportedly reach similar sizes: the American crocodile (Crocodylus acutus) and the Orinoco crocodile (C. intermedius).

Black 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, black 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 black caimans. Dietary studies have focused on young caimans (due both to their often being more common than large adults and to their being easier to handle), the largest specimen examined for stomach contents in one study being only 1.54 m (5.1 ft) notably under sexually mature size, which is at a minimum 2 m (6.6 ft) in smaller females. Although diverse prey is known to be captured by young black caimans, dietary studies have shown snails often dominate the diet of young caiman, followed by quite small fish.[23][24][25][26] Fish were the main prey of black caimans of over subadult size in Manú National Park, Peru.[27] 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. Large prey can include other species of caiman, deer, peccaries, tapirs, anacondas, giant otters,[28] and domestic animals including pigs, cattle, horses, and dogs. Although rare predations on cougars or even jaguars have been reported,[29] very little evidence exists of such predation, and cats are likely to avoid ponds with large adult black caimans, suggesting that adults of this species are higher in the food chain than even the jaguar.[30][31] Where capybara and white-lipped peccary herds are common, they are reportedly among the most common prey item for large adults.[32][33] Evidence has suggested fairly large river turtles can be counted among the prey of adult black caimans, the bite force of which is apparently sufficient to shatter a turtle shell.[34] Scars on Amazon river dolphins suggest they may occasionally be attacked by black caimans.[35] Large males have even been observed to cannibalize other Black Caimans.[36] Compared to the smaller caiman species, the black caiman more often hunts terrestrially at night, using its acute hearing and sight.[10] 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 that the flesh will rot enough to allow the caiman to take bites out of the flesh.

Adult

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.[10] The eggs are quite large, averaging 144 g (5.1 oz) in weight.[13] 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.[10] Hatching is said to occur between 42 and 90 days after the eggs are laid.[10] 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.[10] The female black caiman only breeds once every 2 to 3 years.

Many predators, including various fish, mammal, reptile and even amphibian species, feed on caiman eggs and hatchlings. The black 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. Black 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 black caiman arguably sit atop this food chain. Once the black caiman attains a length of a few feet, it has few natural predators. Large anacondas may take an occasional young caiman of this species. The jaguar (Panthera onca), being a known predator of all other caiman species, is the only primary predatory threat to juvenile and subadult black caimans, with several records of predation on young black caimans and eggs. Adult black caimans have no natural predators, as is true of other similarly-sized crocodilian species given the size, weight, bite force, thick hide, and immense strength; in rare instances, they even may themselves prey upon jaguars.[37][38][39]