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Which is the largest species of crocodile?

Crocodilians suffer from a prevalence of 'big fish' stories and over-exaggeration. However, there is no doubt that some species of crocodiles can attain extremely large adult sizes. It's no surprise that questions over which is the largest are extremely common, and I'll try to shed some light on the answer.

The largest species of crocodile in the world is generally considered to be Crocodylus porosus, the saltwater or estuarine crocodile. In fact, this is the largest living reptile in the world by overall weight. Snake afficionados may argue that there are longer snakes, but none combine both length (over 6 metres) and body mass (well over 1,000 kg) to reach such large overall sizes like the saltwater crocodile can. But there are many arguments, conflicting evidence, tantalising skulls and romantic stories surrounding giant crocs...

hatchling saltie
HATCHLING SALTWATER CROCODILE
How fast do they grow? Hatchling saltwater crocodiles, like the one on the left, emerge from the egg at around 25 to 30cm (1 foot) in length. They can easily sit on the lens of a camera, weighing only 70 grams (2.3 oz). However, they grow rapidly and often exceed 1 m (3.3 feet) in one to two years. The first 10 years of life are accompanied by rapid growth, by which time males are usually at least 3 metres (9.8 feet) in length. Growth slows after reaching sexual maturity (around 10 to 15 years), but typically continues for most of the animal's life (at least 60 to 70 years).

When do they stop growing? It used to be thought that crocodiles would grow indefinitely until they died, and hence that very large crocodiles were always the oldest. However, we now believe that crocodiles in a similar way to other reptiles: very quickly when young, slowing rapidly when older, and reaching a maximum size where growth stops or becomes extremely slow in old age. This means that the largest crocodiles get that way by growing the fastest when younger, and that very old crocodiles are not necessarily the largest. So what influences growth rates when young? Firstly there are genetic factors, and there's no doubt that some individuals are genetically predetermined to grow larger than others - just like humans. Secondly, there are environmental factors such as temperature, food intake and even incubation temperature. There are even social factors, and more dominant animals tend to grow faster than subordinate and stress individuals. So if a crocodile's genetics favour rapid growth, and it has good access to the right temperatures, lots of food, and a dominant social position without stress, it seems more likely to reach a large size. But these giant crocodiles seem few and far between, and the majority of individuals will never attain these monster dimensions. In saltwater crocodiles, for example, the average maximum size for males is around 4.5 to 5.0 metres (14.7 to 16.4 feet). It is extremely unusual to find individuals larger than this - 6 metres (19.6 feet) is a rarity indeed, and only a small handful of individuals have ever been recorded at this length. Don't believe figures that say saltwater crocodiles grow to over 20 feet in length without realising how incredibly rare this is.

In all species of crocodilians, males grow larger than females - this is one of the only reliable ways of telling apart a male from a female (without examining the genitalia), but these differences vary between species. In saltwater crocodiles, males can be twice the length of females, whereas in Nile crocodiles males may only be 30% larger than females. In many crocodile species, males also grow faster than females, but in some (eg. American alligators) females outgrow males for the first few months before being overtaken.

Large saltwater crocodile
LARGE ADULT SALTWATER CROCODILE

Largest captive croc? Burt, in the photograph above, is a captive crocodile in Darwin, Australia. He's over 16 feet (4.9 m) long, which is close to the average maximum size for saltwater crocodiles. There are quite a few crocodiles, however, which are definitely above average. Gomek, in the frame to the right, is a sobering comparison between a decidedly above average crocodile and man. To date, the largest crocodile in captivity is "Yai", who is listed in the Guinness Book of Records at 19 feet and 8 inches (6.0 m) from nose to tail - that was in 2000. Today he's just over 20 feet. Remarkably, Yai was only 30 years old at the time, and at over 1,200 kg he was rather large for his age! Today he's even heavier, though his growth has slowed down dramatically. Yai's growth rate is typical of captive crocodiles kept in optimum conditions with plenty of food. Yai is also a hybrid between C. porosus and C. siamensis - "hybrid vigour" is well known to result in larger, fitter animals in the first generation. There are other zoos that claim to have the largest crocodile in the world, but claims are nothing without accurate measurements, and Yai has certainly been verified. The largest "pure" saltwater crocodile in captivity appears to be "Oscar" - an 18+ foot saltwater crocodile owned by George Craig on Green Island, Queensland Australia. George brought Oscar back from Papua New Guinea along with Gomek several decades ago and, unlike Gomek, Oscar is still going strong.

 
Gomek feeding
   GOMEK FEEDING

Gomek was captured by George Craig in Papua New Guinea and sold to St. Augustine Alligator Farm in Florida. George also captured an even larger crocodile, Oscar, who currently lives on Green Island in Queensland where George Craig now lives. After many years, Gomek unfortunately died of heart disease in February 1997. By this stage, he was a very old crocodile. In this photograph, Gomek is fed nutria (a large rodent) by his keeper, and his size is obvious. When he died, he was 17.9 feet (5.5 m) long - as confirmed by St. Augustine Alligator Farm - and probably between 70 and 80 years old. You can see a tribute to Gomek, including Gomek himself, at St. Augustine Alligator Farm.

   GOMEK
Gomek Largest crocodile ever recorded? What about the big fish stories I mentioned earlier? Would you believe the largest saltwater crocodile ever reported was 10.1 m (33.1 feet)? This animal was apparently killed in the Bay of Bengal, and was so large only its head was recovered. A skull reportedly belonging to this animal was stored in the British Museum, but when it was measured later it was estimated to have come from a 15.7 ft (4.8 m) crocodile - less than half the claimed length. The skull of another claimed 29 ft (8.8 m) monster was also later determined to belong to a crocodile no larger than 16.2 ft (4.9 m). These are still big crocodiles, but typical of the exaggeration normally associated with large crocodiles. Still, some of these stories seem more credible. Saltwater crocodiles above 6 m (19.7 feet) were certainly much more common in Australia and SE Asia before extensive hunting for their skins in the 1940's, 50's and 60's wiped out the big crocodiles. Some old hunters claim to have shot animals over 8 m (26 feet) during this period (e.g. a 27 ft [8.1 m] saltwater crocodile from the Staaton River in Queensland in the early 1970's). But without reliable measurements, such records are lost to the past.

In the Internet age, a new class of "big fish" stories is starting to appear - photographs of crocodiles manipulated digitally to make the animal look much larger that it is. Such tricks are hardly new, and there are dozen of classic "giant crocodile" photographs taken in such a way as to trick the eye into exaggerating the crocodile's size. There's simply no substitute for a measurement taken using a straight tape measure between the tip of the nose and the end of the tail, preferably backed up by reliable witnesses.

So what is the largest crocodile ever recorded? In more recent times, there are very few reliable measurements of extremely large crocodiles, but they do exist. A skull from a saltwater crocodile from Orissa, India, was large enough to have come from a crocodile between 20 and 23 feet in length. Despite being the largest crocodile skull in the world, the true size of its original owner remains a mystery, because although you can estimate total length from skull size, there is enough variation to make such a measurement fairly inaccurate. As far as I can determine, the following are the only two reliable records from &complete& crocodiles over 20 feet in length. The first was a 20.3 foot (6.2 m) saltwater crocodile that became entangled in a fishing net set on the Mary River in the Northern Territory of Australia in 1974. The owners of the net killed the crocodile with an axe and removed the head, but it was eventually discovered by wildlife rangers and the separate head and body measured. The skull is on display at the Darwin Crocodile Farm, and still spots the axe marks that killed it. The second crocodile was also 20.3 feet (6.2 m) long, and was killed by local villagers living on the Fly River in Papua New Guinea in 1983. In this case, it was actually the skin that was measured by several zoologists including Jerome Montague and Rom Whitaker. Because skins are known to underestimate the original size of the actual animal, they concluded that the crocodile was at least another 10 cm / 3.9 inches longer. This is my candidate for the largest crocodile ever measured. Unfortunately, because of the time needed for wild crocodiles to reach this size, the low number of individuals which seem predisposed to reach such sizes, and problems of crocodiles conflicting with expanding human populations, it seems unlikely that we will see many of these giants again.

What about other species? While C. porosus is widely believed to be the species capable of attaining the largest size of any crocodilian, other species occasionally come a very close second. I admit that there's no guarantee that the largest individual crocodilian ever seen was C. porosus, but it is the only species with proof positive of such large individuals. In other species, most of the extreme sizes come from anecdotal evidence which must be treated with a pinch of salt. Very large species include Crocodylus niloticus (Nile crocodile) which is claimed to reach 6 m (19.7 feet) in total length, Crocodylus intermedius (Orinoco crocodile) which may reach 5 to 6 m (16.4 to 19.7 feet), Crocodylus palustris (Indian mugger) which can get up to 5 m (16.4 feet) in length, Gavialis gangeticus (Indian gharial) which is reported to reach 6 m (19.7 feet), Crocodylus acutus (American crocodile) which can reach 6 m (19.7 feet) and for which several unconfirmed reports of 20+ ft animals exist, Alligator mississippiensis which normally only reaches about 4.5 m (14.8 ft) but there is a record of a 19 ft animal, and also Melanosuchus niger (Black caiman) which apparently is capable of reaching 5 m (16.5 feet) - very large for a caiman. These are all maximum sizes, however, and normally most crocodilians do not exceed 3 to 5 m (around 10 to 16.5 feet). None of these species regularly attain the average maximum size seen in C. porosus, although some areas of Africa certainly produce extremely large Nile crocodiles.

But do we really want to know the answer? Perhaps our imaginations remain the best source of inspiration.

Dwarf caiman
CUVIER'S DWARF CAIMAN (ADULT)

Dwarf crocodile
AFRICAN DWARF CROCODILE (JUVENILE)

You may be getting the impression that the world is full of huge crocodilians! This isn't really true - it takes many years for crocodiles to reach these sizes, and only a very few individuals can expect to grow this large. There are also a number of very small crocodilians. Few people ask which is the smallest species, because it's not seen as being very exciting. I disagree - who would think that Paleosuchus palpebrosus (Cuvier's dwarf caiman), Osteolaemus tetraspis (African dwarf crocodile) or Alligator sinensis (Chinese alligator) can only reach maximum length of around 1.2 to 1.5 m (4 to 5 feet). The award for the smallest goes to P. palpebrosus. Curiously, there are also dwarf populations of normally large species such as Nile crocodiles and Australian freshwater crocodiles. When resources are poor, crocodiles simply cannot grow as quickly or to the same maximum size, but one thing's for sure - they make the best use of what's available and survive.

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