There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
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.
This is a very thorough reply, thanks. I will break my response into two parts:
Nile crocodile vs Orinoco crocodile average sizes
I was actually aware of the review by Cott of nile crocodile sizes, what I had actually hoped for was a similar empirical breakdown of Orinoco crocodile sizes, based exclusively on actual measurements. You state “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 greater proportional frequency.” But consider the data we have. “in Venezuela, adult males of Orinoco crocodiles reach 4.1 meters in length on average with a weight of 369 kilograms”. @epaiva states that the largest Orinocos in these populations are around 5 meters. Meanwhile for Nile crocodiles “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” and “Cott's study reported that only seven of these 324 males had lengths ranging from 4.3 to 4.75 meters.” Neither of these two Nile datasets are precisely comparable to the Orinoco one, because they are giving us number of males in certain size classes while the Orinoco data is a population average. In any case, I would not describe the two species’ datasets as “Orinoco’s attaining close to five meters with greater proportional frequency”. I don’t think the data here justifies that claim. At best, I would say that this data suggests the two species have comparable size distributions on average, since the fact that relatively few male Niles are attaining 4.3 plus meters implies the bulk are in the 4.29 and lower range, while the average for male Orinoco crocodiles was 4.1.
Why people say that the Nile crocodile is the second largest species
Your second and third paragraphs on Orinoco crocodile sizes consist of historical anecdotes and some reported measurements on very large Orinocos. I feel that when people are making a list of largest crocodilians, there are a few considerations which cause people to rank the Orinoco crocodile third. People will be looking at the largest reliable sizes, and placing each species as high in the list as it can go based on verified, reproducible high-end measurements. This reproducibility issue is, IMO, the main reason why the order of size is typically given as saltwater-nile-others. If we are to accept the 6 meter plus Orinoco measurements then we would have to actually consider C. intermedius to be the largest crocodilian, because not even salties have reliable measurements of that length on record. However, how large is the data, especially modern data, to substantiate those sizes? By my count we have at least one saltwater crocodile definitively measured at 6 plus meters (Lolong) and two others that were measured piecemeal and can reasonably be expected to have been in that range as well (Old Charlie and the Fly River Crocodile) No other species has verified 6-meter records. Could other species potentially reach this length? I think so, but the measurements aren’t there to support that, so we say that the Saltwater crocodile is the largest. I think we’re really saying that this species has the highest verified upper size range based on the data we have. For the second largest species, there is only one other crocodile with many verified measurements over 5.3 meters, and that is C. niloticus. Brady Barr was able to capture a 5.36-meter Nile crocodile on camera, and the SCI record book has a few specimens over 17 feet as well, including at least two 5.6 meter plus specimens. A dataset set of verified measurements in this size class doesn’t exist for any of the remaining crocodiles, so the Nile is said to be the second largest. No Orinoco or American crocodile has been measured to exceed 5.2 meters (I’ve actually never seen a confirmed measurement over 5 meters) so one of these species is typically said to be the third largest.)
Of course, all these large crocodiles are uncommon, and the bulk of the ecology of these species is mediated by smaller individuals. I think we both agree that the four largest crocodiles are of broadly comparable size and the potential exist for the new world species to one day be measured above 5.5 meters; but, when we want to make a ranked list of species based on size, we have to make reasonable judgement calls based on the empirical measurements, and I think it is this consideration that leads to the commonly cited order of crocodilian sizes.
American crocodile (Crocodylus acutus)
