A 200-pound crocodile drowned? Don't laugh, crocodiles are also afraid of choking on water, okay?

For the crocodile, the "king of the water" in many people's minds, this is a very **"insulting"** trending search...

"The 200-pound crocodile was scared and stayed in the water for a long time and drowned because it was timid."

Image source: Weibo @Cover News

However, on November 16, Professor Gong Shiping, director of the Amphibian and Herpetology Branch of the Chinese Zoological Society and professor of the School of Life Sciences and Technology of Jinan University, believed that under normal circumstances, crocodiles are able to dive and surface to breathe. The reason why this crocodile drowned was probably because it became ill and was unable to swim normally, and it held its breath for too long and could not breathe normally.

So... this news gave us a little-known fact : crocodiles cannot breathe in water like fish, they need to hold their breath in water. And they are very cautious after entering the water...for fear of choking on water.

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Crocodile: I have to be careful not to choke to death...

If you could stick your head into a crocodile's mouth, you'd see... there's a "laryngeal fold" behind the crocodile's tongue, and above the "laryngeal fold," on the roof of the crocodile's mouth, there's a drooping "palatine sail."

When a crocodile is in water with only its nostrils, eyes and ear holes exposed above water, the "palatine velum" and "laryngeal folds" act like switches that can be opened and closed freely, separating the crocodile's respiratory tract and oral cavity. In this way, the external nostrils are exposed above water for normal breathing, and the ear holes are also exposed above water. The protection of the "switch" underwater can also prevent water from entering the mouth.

When a crocodile subdues its prey in the water and cannot breathe, in addition to closing the "palatine velum" and "laryngeal folds" to prevent water from entering the mouth, it will also "activate" the "muscle valves" of the external nostrils and ear holes to prevent water from entering the nasal cavity and ear canal.

In order to avoid choking on water, the crocodile is extremely cautious and takes great pains.

The breathing control structure of the crocodile (Source: Zhao Kentang)

Eh, I seem to have discovered something incredible - why can a crocodile sometimes be in the water with only its nostrils, eyes and ears exposed? Isn't this the general posture of a crocodile on the water?

Crocodile's "horizontal floating" posture (Source: trishansoz)

Yes, the crocodile floating posture we commonly see is called "Horizontal Float", that is, the crocodile is motionless on the water surface, with part of the upper body floating above the water surface, and the legs are spread out as a "stabilizer" to prevent the body from rolling. It may also gently shake its tail to maintain its position in the flowing water.

The question is, how can it be said that “only the nostrils, eyes and ear holes are exposed above the water”, but there are many other parts that are “exposed”?

In fact, this posture is what crocodiles have to do in deep water. From above we also know that to maintain this posture, sometimes they have to use their feet and sometimes their legs, which is not very strenuous!

When they reach shallow water, some crocodiles will adopt another cute posture : vertical floating, that is, their hind limbs and tail sink to the bottom of the water, looking like a person in a bathhouse.

With this posture, only the nostrils, eyes and ear holes of the crocodile are exposed above the water. This not only allows the crocodile to see, smell and hear what's happening around it, but also allows it to avoid being discovered by its prey, saving energy. It also makes it less likely to choke on water accidentally because of the need to maintain a "horizontal floating" posture. It's quite fun!

Crocodile's "vertical floating" posture (Source: wiki)

In 2015, a Twitter user shared a picture of a crocodile in a breeding farm underwater, which became a hot topic at the time.

(Source: Japanese News)

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The "lone crocodile" in the modern ocean - the saltwater crocodile

Suddenly a strange association came to my mind. Generally speaking, compared with the sea, waters such as rivers, lakes and swamps are considered shallow. How can a crocodile with such a "poor appearance" (just kidding) swim in the sea?

This question is really heartbreaking. In modern oceans, although the prosperity of reptiles cannot be compared with that of fish, there are also animals such as marine snakes and marine turtles.

According to statistics from the New Reptile Database, there were 17 genera and 69 species described as marine snakes worldwide by the end of 2008. Although there are relatively few marine turtles, according to statistics from websites such as seaturtle and iTurtle, there are also 7 species, including leatherback turtles, loggerhead sea turtles, Kemp's ridley sea turtles, olive ridley sea turtles, hawksbill sea turtles, green sea turtles, and flatback sea turtles.

In contrast, the only marine crocodile that biologists can observe at present is the saltwater crocodile , which is known as the largest in the crocodile family. An adult male can generally reach 5 meters in length and weigh 300-400 kilograms. In September 2011, a giant male individual captured in the Bunawan River in the Philippines weighed more than 1,000 kilograms and was 6.17 meters long. It is the largest individual observed so far and is called Lolong.

Lolong imprisoned in the Bunawan Creek Ecological Tourism Park (Source: wiki)

However, although the saltwater crocodile is large in size and dares to be a "lone crocodile" roaming the ocean, its activities in the ocean are actually quite limited , and it is not fully adapted to marine life.

1. Activity range: Bays, seaports, and especially the "delta" areas where rivers flow into the sea. Generally speaking, they basically move along the coast and generally do not go "overseas".

2. Nesting location: Nests are built in hilly areas with plants as "cover" beside freshwater rivers, which are tens to hundreds of kilometers away from the estuary. This is farther from the sea than the nests built on the beach by many turtles.

A saltwater crocodile "surfing" on the coast of the Philippines (Source: wiki)

So, in general, although the saltwater crocodile has a terrifying hunting ability that shocks all around, it has not changed the "decline" of the crocodile in the sea...

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The short-lived "marine crocodile"

Have crocodiles always had such bad luck in the sea? Not exactly.

Since the early Jurassic period, reptiles similar to modern crocodiles have existed on Earth. At that time, they were mainly divided into "two major camps", one of which was the more primitive Mesosuchia, and the other was the Eusuchia, which has continued to thrive to the present day.

Among the Mesozoic crocodiles, some began to crawl towards the sea in the early and middle Jurassic period, gradually adapted to marine life, and rode the waves in the vast ocean. These are marine crocodiles .

Many members of the marine crocodiles have become very "strange" in shape, such as their forelimbs have been transformed into "flippers" that resemble fish fins, and their tails have become "crooked fins". Some paleontologists believe that the unique body shape of marine crocodiles is just a variation to adapt to marine life.

These marine crocodiles were very courageous to be able to roam the ocean during the Mesozoic Era when "dragons went to the sea". However, the prosperity of marine crocodiles was only short-lived. We can get some clues from the survival time of some species in this family.

Marine crocodiles are mainly divided into two "teams": Teleosauridae and Metriorhynchidae.

A reconstruction of the true sauropod drawn by Dutch zoological illustrator Joseph Smit in 1894 (Source: wiki)

From the restoration pictures or fossils in the table above, we can see that the snouts of the Eusauriformes were really long , just like the "previous life" of modern gharials. They were also very "slender", but their forelimbs were pitifully short. Paleontologists speculate that they might have kept their forelimbs close to their bodies when swimming to increase their maneuverability in the water.

It is worth noting that the fossils of some early members of the family Eusaurosuchidae were found in "non-aquatic" habitats, which is strong evidence that marine crocodiles evolved from "semi-aquatic crocodiles" to "fully aquatic crocodiles".

The forelimbs of the Mesorhynchidae were reduced and paddle-shaped, and they lost their intradermal osteophytes. They had fish-like fins on their tails. Their bodies were more adapted to marine life than those of the Eusauridae and were more fish-like. They were truly "crocodiles."

Combining Table 1 and Table 2, we can see that the entire marine crocodile family, including the Eusauridae and Mesorhynchidae, survived for only about 50 million years, from the early Jurassic to the early Cretaceous. Compared with their "rivals" who roamed the sea together, they are simply "a dwarf compared to a giant". For example, the famous plesiosaur family lasted for about 130 million years, and the ichthyosaur family lasted for about 160 million years!

One of the "ancestors" of the ichthyosaur family, lived in the early Triassic period **"Hupehsuchus"** (Hupehsuchus) is about 248 million = 247 million years old. It was named because its fossils were found in Hubei Province, China and its appearance resembled a crocodile (Source: wiki)

One of the youngest members of the ichthyosaur family, Platypterygius lived in the Cenomanian stage of the Early Cretaceous period, about 130 million to 94 million years ago. It was named because its front flippers had more fingers than ordinary ichthyosaurs, and they were closely arranged to form a broad, flat shape.

It turns out that crocodiles are not as comfortable in the water as we thought... But, let's get to the beginning - who scared the crocodile? It's so unreasonable. It should just be an introverted, socially anxious and inferior little thing.

References:

Zhang Mengwen: Fauna Sinica Reptiles Volume 1: General Introduction to Testudines and Crocodilians, Science Press, 1998

Xing Lida, Yang Helin: The Biography of Hailong, Aviation Industry Press, 2009

Crocodile Biology Database

Elapidae Archived 2008-10-11 at the Wayback Machine at the New Reptile Database. Accessed 12 August 2007.

Hutchings, Pat (2008). The Great Barrier Reef: Biology, Environment and Management. Csiro Publishing. p. 345. ISBN 9780643099975. Sea snakes are true reptiles closely related to Australian venomous terrestrial snakes. Indeed, both groups are included in a single subfamily, Hydrophiinae, by most modern herpetologists.

""Lolong" holds world record as largest croc in the world". Biodiversity Management Bureau. 17 November 2011. Retrieved 8 January 2016.

Britton, Adam (12 November 2011). "Accurate length measurement for Lolong". Croc Blog. Retrieved 8 January 2016.

Fitzinger LJFJ. 1843. Systema Reptilium. Wien: Braumüller et Seidel, 106 pp.

Steel R. 1973. Crocodylia. Handbuch der Paläoherpetologie, Teil 16. Stuttgart: Gustav Fischer Verlag,116 pp.

The author of this article: Archaeology Xueqi, Master of History from Wuhan University, majoring in Shang and Zhou Dynasty archaeology.

Source: Tadpole Musical Notation

Editor: Heart and Paper