at their nests was found to be . Mid-sized mature males of weigh approximately , while large mature specimens exceed , being relatively bulky crocodilians. 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 subadult males found them to range in length from , averaging , and that they weighed from , averaging . 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 . 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. 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 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, as well as molluscs, 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 notably under sexually mature size, which is at a minimum 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. Fish were the main prey of black caimans of over subadult size in Manú National Park, Peru. Various prey will be taken by availability, includes snakes, turtles, birds and mammals, the latter two mainly when they come to drink at the