Beauty and the Beast
In people's minds, crocodiles are "evil fish". When you think of crocodiles, you immediately think of the blood basin mouth, dense sharp teeth, full body hard armor, ready to eat people. Crocodile is a cold-blooded oviparous animal. Crocodiles are extremely precious animals. Crocodiles are not fish, they are reptiles, the name of crocodiles, or because they play in the water like fish, so they are named "crocodiles".
The crocodile is one of the earliest and most primitive animals found alive so far, appearing in the Mesozoic Era from the Triassic to the Cretaceous Period (about 200 million years ago), a fierce vertebrate reptile, it and dinosaurs are contemporaries of animals, carnivorous. There are 23 species of recognized crocodiles.
The types of crocodiles domesticated and bred in China are: Yangtze crocodile, Siamese crocodile, bay crocodile, Nile crocodile; among them, there are three kinds of crocodile species allowed by the state to operate and use: Siamese crocodile, bay crocodile, and Nile crocodile. Among them, the Siamese crocodile (also commonly known as the Thai crocodile) is a crocodile that is widely domesticated in the north of China. The unit that issues the crocodile domestication and breeding certificate is the State Forestry Administration.
The Siamese crocodile was internationally recognized as extinct in the wild in 1992, but experts have since conducted some surveys and found that a small number of individuals remain in Thailand's Pang sida National Park and Ang Lue Nai Wildlife Sanctuary.
Crocodiles are wild animals of high ecological, scientific and economic value. Therefore, some countries in the world are actively developing crocodile farming.
Crocodile, climbing skill
The latest research has found that climbing is a common behavior of crocodiles. They gain better hunting positions by climbing, or get the largest possible area of exposure to sunlight. Britton, a researcher at Charles Darwin University, said he had witnessed the 1.5-meter-long freshwater crocodile climb up the steep riverbank and try to climb the 1.8-meter-high fence. "Not only do crocodiles lean against the shore to bask in the sun, they sometimes walk around. Crocodiles are actually very sensitive animals, and their sensitivity is even beyond human imagination. ”
Crocodiles attack elephants, and saltwater crocodiles are more dangerous than their close relatives, freshwater crocodiles.
Crocodile tears
Crocodiles do shed tears, but that's not because it's sad, it has long been thought that crocodiles are excreting excess salt in their bodies. Some marine reptiles, such as sea turtles, sea snakes, sea lizards, and some seabirds, have salt glands near the eye sockets. Salt glands allow these animals to remove excess salt from seawater and thus obtain fresh water. Therefore, the salt glands are their natural "desalinators". So people think that crocodile tears are also the reason. The excretion function of the crocodile kidney is very imperfect, and the excess salt in the body depends on a special salt gland to excrete. The crocodile's salt glands are located right near the eye.
Crocodiles excrete salt by secreting fluids on their tongue rather than tears. So, what role does crocodile tears play? Crocodiles usually spend a long time on land before they begin to secrete tears, which are secreted from behind the transient membrane. The transient membrane is a transparent layer of eyelids, when the crocodile dives into the water, close the transient membrane, which can not only see the situation under the water, but also protect the eyes. Another function of the transient membrane is to moisturize the eyes, which requires the use of tears to lubricate.
Image: judy gallagher / flickr cc by 2.0
Crocodiles don't really cry when they eat. Kent Vliet, a zoologist at the University of Florida, observed and photographed four caimans and three alligators eating on land at a crocodile farm in 2007 and found that five of them did cry while eating, and some even foamed their eyes. They eat processed foods like dog food, and of course they can't cry over these foods. Fleet speculated that this was because the crocodile was accompanied by a blow when eating, and the air and tears that pressed the sinuses mixed together and flowed out.
China's national treasure - Yangzi crocodile
Yangzi crocodile, also known as shrew, pig dragon, etc., the adult length of about 1.5 to 2 meters, weight of about 30 to 45 kg, is one of the smallest species of existing crocodiles.
The Yangtze crocodile's face is obviously more kind. Image: Greg hume / wiki commons
The ancient Chinese account of the Yangzi crocodile dates back to the Yin Shang era more than 1700 BC: according to records such as the Oracle Bone Compilation, there are nine texts about reptiles that can be recognized in the oracle bone, and the Yangzi crocodile is prominently listed, and at that time people called it a mole. Later classics such as "Poems", "Ritual Records", "Commentaries on The Interpretation of Texts", and "Naturalist" also recorded a lot of information about the Yangtze crocodile.
In addition, according to fossil evidence, in the Neolithic period, the historical distribution range of the Yangtze crocodile can be at least covered from Tai'an in Shandong to Yuyao in Zhejiang, and the population should also be very considerable.
On the Bronze Stele of the Shang Dynasty in the Shanxi Museum, crocodile patterns are depicted. Image: zcm11 / wiki commons
In the middle of the last century, due to the large number of habitats used to develop arable land or residential areas, the confrontation between the human crocodile was inevitable. On the one hand, worried that crocodiles hurt people, on the other hand, worried that crocodiles will destroy fisheries and agricultural production, And The Yangtze crocodile was eventually forced into a desperate situation.
In just 30 years, the population has decreased by nearly 90%, and the wild population only remains in Anhui and Zhejiang provinces, with less than 200 tails. Thanks to the timely protection and the great success of artificial breeding, the artificial population of Yangzi crocodiles has reached nearly 20,000, and the related field release work is also continuing.
Contrary to their fierce appearance, the Yangtze crocodile is timid and shy, and will not attack humans unless they take the initiative to provoke, and they mainly eat snails, crabs, fish and water birds, which have little impact on fishing and agricultural production. Many foreign scholars believe that crocodiles prey on prey while also eating the carcasses of other animals, which plays a vital role in maintaining the cleanliness of water bodies and the ecological balance of wetlands.
Yangtze crocodile in Shanghai Zoo. Image: J. patrick fischer / wiki commons