American crocodile (Crocodylus acutus)

[Balam]

@KRA123

The breeding facility Patrullero de Chávez, dedicated to the conservation of Orinoco crocodiles, plays an active role in managing these reptiles for breeding purposes, with the distinct advantage of having them in captivity. Such facilities follow strict protocols, including regular veterinary assessments to ensure the well-being and accurate measurements of the crocodiles. It's important to note that this measurement is particularly reliable because it pertains to one of the largest breeding males in the facility which fell well within the range of large contemporary males as mentioned by @epaiva.

It's also true that all crocodile species face challenges when it comes to surpassing the 5-meter length threshold, and this is a reflection of the natural constraints on their growth. However, the main point of contention is not that Nile crocodiles are unable to achieve such lengths but rather that despite their widespread reputation as the "second-largest" crocodile species in the world, they appear to encounter comparable hurdles in reaching this notable milestone. What adds to the intrigue is that American and, particularly, Orinoco crocodiles have grappled with overhunting, which has led to significant impacts on their average sizes due to genetic diversity erosion.

Even in the face of this adversity, American and Orinoco crocodiles continue to produce individuals that attain asymptotic sizes of 5 meters or close to it with greter proportional frequency. In contrast, Nile crocodiles boast a larger population and healthier genetic diversity, yet they seem to exhibit a comparatively lower frequency in achieving these impressive lengths. This intriguing observation casts a shadow of doubt on the claim that Nile crocodiles are unequivocally the second-largest in the world, as their counterparts from the Neotropics show a remarkable ability to achieve similar sizes despite their less favorable conservation status.

Now in terms of size, this is the information I have:

In the 2017 Growth rates of the American crocodile paper by Andrés E. Seijas, growth rates for American crocodiles were analyzed from various regions. The von Bertalanffy growth model predicted an asymptotic size of 4.39 meters for males in Florida. As for females, asymptotic sizes were 2.617 meters for those in Florida and 2.274 meters for those in the mangroves of Venezuela.

The Comportamiento reproductivo del caimán del Orinoco by Colvée (1999) reported that in Venezuela, adult males of Orinoco crocodiles reach 4.1 meters in length on average with a weight of 369 kilograms. Females reach up to 3.2 meters in length and weigh around 211 kilograms.

Experts generally estimate a maximum total length of up to 7 meters for Orinocos. This estimation is substantiated by the accounts of seasoned "caimaneros" or crocodile hunters, such as those cited by Medem in 1981. Even historical explorers like Humboldt and Bonpland, who ventured along the banks of the Apure River in 1880, recorded their encounters with remarkably large Orinoco crocodiles. One account describes a specimen measuring 16 feet 8 inches (508 cm) in length, while another, identified as a male, stretched to an impressive 22 feet 3 inches (678 cm). Further back in time, the narrative continues with Fray Jacinto de Carvajal, who, in 1618, chronicled a colossal crocodile of 25 feet, which, adjusted for the "pie de Castilla" measurement system (27.85 cm per foot), translates to an astonishing 696 cm. These historical and contemporary records paint a vivid picture of the remarkable size potential of the Orinoco crocodiles during a time when they were not critically endangered. 

Humboldt and Bonpland are as reliable as a naturalist could get for the 19th century, which is why they are quoted by modern authorities in the field, like in the Commercial Hunting of the Orinoco Crocodile, Crocodylus intermedius, in Venezuela thesis by Ernesto Boede and Rafael Hoogesteijn (2017) where they detail Alexander von Humboldt's extraordinary journey to the Orinoco region in detail. He noted that crocodiles were abundant and that sizes ranged between 5.08 meters to 7.31 meters. It's possible that the 7.31 meters value is an incorrect conversion belonging to the 6.78 meters specimen to be clear.

For Nile crocodiles, we have B. Cott's paper, Scientific results of an inquiry into the ecology and economic status of the Nile Crocodile (Crocodilus niloticus) in Uganda and Northern Rhodesia which sheds light on the challenges associated with assessing the size of Nile crocodiles. The study underscores the skepticism surrounding the validity of size records and highlights the unreliability of visual estimates, such as those provided by herpetologists like Brue (7.62 meters) and Barbot (9.14 meters). While some herpetologists have erred on the side of caution, accepting a conservative estimate of 4.88 meters, this figure is notably lower than the measurements reliably reported from historical accounts.

Cott's work presents a range of maximum lengths reported for Nile crocodiles from different African regions. In Central Africa, reports suggest that large crocodiles over 4.99 meters in length have been encountered. For instance, the largest crocodile measured in Northern Rhodesia reached 5.05 meters. Similarly, a crocodile in Nyasaland was reported to measure an impressive 5.74 meters.

In East Africa, particularly in Uganda, the study highlights the presence of exceptionally large Nile crocodiles. Crocodiles in the Lower Semliki and the Murchison reach of the Victoria Nile achieved notable sizes. In 1950, two males measured 5.13 meters and 5.54 meters, according to measurements taken by a Game Ranger. Additionally, in 1952, the Marketing Corporation received a skin measuring 5.94 meters from the Lower Semliki, signifying the substantial size of Nile crocodiles in this region.

So what does contemporary data says? A. D. Graham's 1968 study, The Lake Rudolf Crocodile (Crocodylus niloticus Laurenti) Population, provides valuable insights into the population and growth characteristics of Nile crocodiles in the Lake Rudolf region. The study reveals that sexual maturity in this population is reached by over 50% of males at approximately 2.7 meters in length. However, there is substantial variability in the size at which crocodiles become sexually mature, with some individuals reaching maturity as early as 1.89 meters, while others require up to 3.38 meters.
The study records that among the 202 males examined during the survey, the largest individual measured 4.72 meters, with an additional 11 crocodiles falling within the range of 4.3 to 4.7 meters. Notably, in the Lake Rudolf area surveyed by the Kenya Game Department in Ferguson's Gulf, no crocodiles larger than this maximum size were encountered.

Additionally, A. D. Graham references findings from B. Cott's study in Uganda and Zambia, which examined 324 males. Cott's study reported that only seven of these males had lengths ranging from 4.3 to 4.75 meters. But as I showed before Cott's work also cites several seemingly authentic records of Nile crocodiles reaching lengths of up to 6 meters. Graham highlights personal records of crocodiles exceeding 5 meters in length from the Grumeti River in Tanzania as well. This suggests that while there is a common upper limit for Nile crocodile size, exceptionally large individuals occasionally surpass this threshold, but they are far from common.

I believe that the idea of Nile crocodiles being the undisputed runner-up for sizes in crocodiles is just a lazy generalization that has been accepted through time, particularly when we take into account that Nile crocodiles are significantly better-known and documented than Orinoco crocodiles, this generates a bias to place more importance to them even when the empirical data doesn't support those assertions.

I believe that under the right conditions, all four of the largest crocodiles in the world can attain similarly gigantic sizes: salt-water, Orinoco, Nile, and American, but we don't live in a perfect world and the degrees of conservation between these species vary greatly, so we must have a large degree of nuance when we make definitive claims about their sizes. Reply