Orinoco crocodile

In spite of its somewhat narrow snout, the Orinoco crocodile is both a formidable apex predator and one of the world's largest reptiles.

The Orinoco crocodile ranks among the largest living reptiles, as well as the largest predator in the Americas. It is arguably, on average, the largest crocodilian in the Americas; while American crocodiles, black caimans and the American alligator may approach similar dimensions, the Orinoco crocodile may be (or had been, when in healthy numbers) slightly longer.[9] Given its possible maximum sizes, the Orinoco crocodile may rank as the third largest extant true crocodile, after the saltwater crocodile and Nile crocodile (which is closely related to it, despite its substantially different range), and additionally rank 4th amongst all extant crocodilians behind the gharial, though there is little to suggest that Orinoco specimens in modern times can rival these species.[7][9] Sexual maturity for Orinoco crocodiles is obtained for females at around 2.5 m (8 ft 2 in) while that of males seems to be obtained around 3 m (9 ft 10 in) length, with most adult crocodiles of the species exceeding 93 kg (205 lb). Average length of wild adult females from 1985 to 1992 was found to be 3.06 m (10 ft 0 in) while that of males is not known to have been surveyed at that time.[10][11] If not culled by humans, mature males easily exceed 3.6 m (12 ft) and attain a length of as much as 4.1 to 4.8 m (13 to 16 ft) as they grow throughout life, perhaps weighing 500 to 700 kg (1,100 to 1,500 lb) in big specimens, while females may grow over the expected size of 3.25 m (10 ft 8 in) in length and may sometimes exceed 225 kg (496 lb).[12][13] According to Guinness Records, the average length of adults that they were able to examine was only 3 m (9 ft 10 in) and the largest specimen found firsthand was 4.2 m (13 ft 9 in).[9] In captivity, at the Roberto Franco Tropical Biological Station (EBTRF), the largest male was recorded at 4.2 m (13 ft 9 in) and weighed 428 kg (944 lb), and maximum size recorded for females was 3.9 m (12 ft 10 in) long and 195 kg (430 lb) in weight. In Venezuela, males have been reported to reach at least 4.1 m (13 ft 5 in) in length and weigh 380 kg (840 lb), while females reach up to 3.2 m (10 ft 6 in) and weigh up to 210 kg (460 lb).[14] The largest specimen historically reported was shot in 1800, and allegedly measured at 6.78 m (22 ft 3 in), although the source is considered reliable, unfortunately, no voucher specimen is known from this.[15][16] Because of extensive hunting for their skins in the 20th century, such giants do not exist today, and modern Orinoco crocodiles have not been reported to exceed 5.1 m (16 ft 9 in) in length.[9] Merchán listed the maximum total length attainable for a male as 5.2 m (17 ft 1 in) and the maximum length of a female as 3.6 m (11 ft 10 in).[17]

The hunting strategy of the Orinoco crocodile

Little study has gone into the dietary biology of Orinoco crocodiles but from eye-witness accounts and partial studies from captivity and crocodile farms, the majority of the Orinoco crocodile's diet appears to consists of large fish. The species' relatively narrow snout is ideally suited to minimize water resistance in capturing such aquatic prey. However, as an opportunistic apex predator, virtually any animal living within its range could be considered a potential meal, such as invertebrates,[18] reptiles, birds, and mammals. Despite having a rather elongated skull, its base snout is wide, hinting to a generalist diet. Additionally, as they age, mature males in particular appear to manifest a broadened snout, presumably due to a shift to being able to take larger prey as is seen in several other large crocodile species.[19] It stalks both aquatic and terrestrial prey. As a large adult, terrestrial prey may include monkeys, deer, birds, other reptiles, domestic animals, and even occasionally other large predators if the opportunity arises.[7] Similar to many of the larger crocodile species, the Orinoco crocodile has also been observed catching and eating smaller species of crocodilians, such as adult common caimans and sometimes cannibalizing smaller individuals of its own kind.[20]

An Orinoco crocodile splashes into the water in the savanna near Mani, Colombia.

Attacks on humans have been reported, but this is highly unlikely to be a common behavior today, given the very small population of the species and its relative isolation from large human settlements. Historically attacks were not unusual and on his trip to the region in 1800, natives told Alexander von Humboldt that two or three adult people were killed per year by Orinoco crocodiles.[21] A small number of better documented fatal attacks were reported in the 1900s–1930s when the species was still relatively common.[22] The only well-documented recent attack, on a fisherman in 2009, was serious but not fatal.[21][23] A second survivor was reported in 2011 to live in La Palmita at the Cojedes River, but any details of this attack (including when exactly it happened) are lacking.[21]

Orinoco crocodile's head

When water recedes in the dry season, Orinoco crocodiles retreat to burrows they excavate into the riverbanks. The adult pair mates during the drier period of the year. Adult males attract the females by roaring. The females often outnumber the males two to one and appear to select the males with the deepest roars.[24] In a reintroduced population, only 6 of 14 potential adult males parented over 90% of eggs laid.[25] Usually 14 weeks after mating, the female crocodile will dig a nest and lay about 40 eggs. It is a hole-nester, as are all crocodilians, and it usually makes its nest on a sand bank. The eggs incubate under a mixture of soil and rotting vegetation for around three months. The most common predator of buried eggs are tegu lizards although the tegus are sometimes caught and killed by the mother crocodile.[25][26] During the night the young hatch and call to their mother; she digs them out of the nest and carries them to the water, which is considerably higher at this point. Young Orinoco crocodiles are often at risk from predation by American black vultures, tegu lizards, anacondas, caimans, coatis, jaguars, and other carnivores, though these species are sometimes also caught and killed by the defending mother crocodile. Adults have no predators except for humans. Females have defended pods of juveniles for over three years, though closer to one year to independence is generally most common.[7] A study of captive Orinoco crocodiles noted the aggressive behavior of adults while nesting and noted that the normally relatively docile crocodilians could not be approached while they were actively brooding.[27] Without persecution, it is possible that Orinoco crocodiles may reach a lifespan of 70–80 years.[7]