Snakes also like to take hot spring baths

In ancient times, the Qinghai-Tibet Plateau was a vast ocean, which connected with the present Mediterranean Sea and the Atlantic and Pacific Oceans. This vast ocean is called the "Ancient Mediterranean". To the north of the Ancient Mediterranean was the Laurasia continent, which included parts of today's Europe, Asia and North America. To the south was the Gondwana continent, which included parts of today's South America, North Africa and Australia, as well as Antarctica, South Asia and other parts.

Geologists believe that about 240 million years ago, due to the movement of the earth's plates, the Indian Ocean Plate (now the South Asian subcontinent and most of the Indian Ocean) separated from Gondwana moved northward, squeezing the ancient Mediterranean Sea, causing strong folding, fracture and uplift in the area. As a result, the Kunlun Mountains and the Hoh Xil region rose to become land at that time.

210 million years ago, the crust in the north of the ancient Mediterranean Sea began to become active, and the current northern Qiangtang area, Karakoram Mountains, Tanggula Mountains and Hengduan Mountains became land. 80 million years ago, the Indian Ocean plate continued to squeeze northward, causing the Gangdise Mountains and Nyainqentanglha Mountains to rise sharply, making northern Tibet and parts of southern Tibet also become land. This formed the prototype of the current Qinghai-Tibet Plateau and also formed a paradise for many terrestrial animals.

Figure 1 Schematic diagram of the six major sectors (Source: Internet)

For a long period of time in the early and middle Cenozoic Era, there was a low-altitude valley running east-west in the middle of the Qinghai-Tibet Plateau. The Gangdise Mountains and the Tanggula Mountains are to the south and north of the valley respectively. The monsoon from the Indian Ocean created a tropical and subtropical warm and humid forest here. During this period, it bred many creatures, including some snakes closely related to the American Snail Snake.

However, they did not expect that this valley has been squeezed by strong forces from both the north and south for tens of millions of years, gradually narrowing. In the Neogene 23 million years ago, this valley was further squeezed and filled, gradually reaching its current height. The southeastern edge of the Qinghai-Tibet Plateau also experienced a certain degree of uplift between the late Eocene and the early Oligocene, and reached its current height.

Since then, the Qinghai-Tibet Plateau has developed a climate characterized by strong ultraviolet rays, lack of oxygen, and cold weather. The once thriving forest scene has become the current alpine shrub meadow, alpine grassland, alpine desert, etc. Many species have disappeared or migrated away in such geological changes. Some species have stayed here, found the right way, evolved special abilities, adapted to this special environment of lack of oxygen and high ultraviolet rays, and formed unique species.

Figure 2 Tibetan hot spring snake (Source: China News Service, photographed by Huang Song)

Hot spring snakes are snail-eating snakes that were stranded here during the uplift of the Qinghai-Tibet Plateau. Hot spring snakes are the snakes with the highest altitude distribution in the world, with an altitude of 3,500 to 4,400 meters. They are also the most special type of snakes on the Qinghai-Tibet Plateau, and they are not found anywhere else. The complex geological changes of the Qinghai-Tibet Plateau have isolated them in three different places, forming three different species, namely the Tibetan hot spring snake in central Tibet, the Sichuan hot spring snake in western Sichuan, and the Shangri-La hot spring snake in northern Yunnan. They mainly live in stone piles, waterside and swamp meadows near hot springs, and have become representatives of different regions on the Qinghai-Tibet Plateau.

Millions of years ago, when the Qinghai-Tibet Plateau was rising, their ancestors found a few small places to live - hot springs. There are abundant geothermal resources here, and underground hot springs keep gushing out of the ground all year round, forming a warm and humid microclimate. The ancestors of hot spring snakes successfully survived the ice age and interglacial period here and evolved into the current hot spring snakes. There may be no other type of snake that relies on hot springs like hot spring snakes. A warm and humid microclimate is maintained here, with stone piles, hot spring ponds and swamp meadows, and nests heated by hot springs. The ancestors of hot spring snakes have relied on small vertebrates in the hot spring water area for food, such as frogs and fish that have adapted to high altitude environments like them.

Figure 3 Shangri-La Hot Spring Snake (Source: China News Service, photo by Peng Lifang)

The closest relatives of the hot spring snake are the linear snakes distributed in the Qinling Mountains. They are the only two types of snakes in the family of snail-eating snakes in Asia, and the other family members are in America. It is speculated that the long-term cold climate during the Ice Age may have led to the extinction of snail-eating snakes in other parts of Asia. The linear snakes may have survived due to the complex terrain and lower altitude of the Qinling Mountains, while the hot springs on the Qinghai-Tibet Plateau have preserved the hot spring snakes.

In addition to facing the cold, hot spring snakes also face hypoxia and extremely strong ultraviolet radiation. Scientists have found that the microclimate formed by hot springs allows them to avoid the threat of cold, but hypoxia and strong ultraviolet radiation are likely related to their gene mutations. Scientists have found many mutations in the genes of hot spring snakes, and most of these gene mutations are related to functions such as immunity, hypoxia adaptation response and DNA repair. Some mutant genes have stronger stability under ultraviolet irradiation, which may help hot spring snakes resist high-intensity ultraviolet radiation. Some mutant genes can cause the hemoglobin concentration of hot spring snakes to be at a lower level, which may help hot spring snakes adapt to high-altitude hypoxia.

Figure 4 Tibetan hot spring snake (Source: National Natural Science Foundation of China website, photo by Zhou Zhengyan)

However, the harmless and non-toxic hot spring snakes resisted the harsh natural environment, but could not resist the destruction of their habitats. At present, many hot springs on the Qinghai-Tibet Plateau have been developed, and the construction and human activities near the hot springs have made the survival of hot spring snakes very poor, and their population has dropped to an extremely dangerous level. In February 2021, the newly revised "National Key Protected Wildlife List" included all three species of hot spring snakes in the national first-level protection. I hope that under the relevant laws on wildlife protection and the protection of people, they can always reproduce and thrive in health on the Qinghai-Tibet Plateau.

(Source: Science Press, Author: Cai Bo)