Producer: Popular Science China
Author: Kehai Shibei
Producer: Computer Network Information Center, Chinese Academy of Sciences
"Ding-dong, ding-ding, ding-ding-ding..." Whenever this string of beautiful melodies rings in the ears, the children's minds will surely flash a picture like this: small snowflakes floating in the sky, Santa Claus riding a sleigh full of gifts, pulled by a group of cute little animals... Wait, a bunch of sled dogs? Or a herd of horses?
Reindeer (Image source: Baidu Encyclopedia)
In fact, the legend of santa claus to pull the sleigh is the long-horned animal in the picture above, the scientific name is called reindeer. There are nine reindeer pulling sleighs: the leader is Rudolph, whose shiny red nose helps Santa Claus find the chimney on a snowy day, and the other eight reindeer who contribute also have their own names.
So why did Santa Claus choose reindeer as a means of transportation, rather than a horse or other animal?
< h1 class="pgc-h-arrow-right" > why reindeer? </h1>
I have to say that Santa Claus is very smart and chooses the most suitable means of transportation for his work. The legendary Santa Claus came from the far North Pole, and the reindeer happen to be widely distributed in the Arctic Circle. Some reindeer were domesticated by humans very early on and became the main production and transportation of the local people, enjoying the reputation of "the boat of the mountains and forests".
The reindeer (Rangifer tarandus), also known as the horned deer, belongs to the reindeer genus of the deer family. Adult reindeer can reach a length of 2 meters and a shoulder height of about 1 meter. The reason why the ancestors of human intelligence chose reindeer as the object of domestication of transportation is mainly because they have the magic weapon of polar survival.
First of all, the hooves of reindeer are very suitable for snow running. Its hooves are broad in the palm and are the largest of the deer. Large amounts of bristles grow on the fibula side, tibia side and around the sole of the foot, like a pinch of thick brush. Wearing such a pair of reinforced snow boots, whether walking in snow, swamp or moss, can reduce the weight of the load per unit area by increasing the contact area with the ground.
Reindeer feet and fur on the fibular, tibia and soles (Image: Reference 9)
At the same time, the hooves of reindeer can also adapt to the seasonal changes. When the tundra is soft and moist in the summer, the reindeer's foot pillows turn spongy to provide more friction. When winter comes, the foot pillows shrink and solidify, revealing the edges of their hooves, which is not only convenient for the reindeer to walk in the snow and ice, but also convenient for it to pull out the snow piles in search of food.
Second, the reindeer's eyes are able to catch ultraviolet rays. Legend has it that Rudolf's nose can change color, but in fact in the natural environment, it is the reindeer's eyes that can change color. Geoffrey Glenn, a neuroscientist at the University of London, has conducted 12 years of research in harsh Arctic conditions to unravel the mystery of reindeer eye discoloration.
Reindeer eyes are dark blue in winter and golden yellow in summer (Image: Reference 6)
The researchers pointed out that the color of reindeer's eyes is regulated by a reflective layer called the illuminated membrane located behind the retina, and the density of the collagen fibers located in the irradium can change the intensity and wavelength of the reflected light.
In winter, the pressure on the reindeer's eyeballs increases, the collagen fibers are tightly packed together, and the light is more likely to scatter in the deer's eyes, and it is mainly short wavelengths, showing a dark blue color. In summer, on the contrary, more light is reflected by the retina, so it appears golden.
Light that enters the reindeer's eyes in winter is more likely to scatter and is dominated by short wavelengths (Image: Reference 6)
At the same time, the researchers note that many objects tend to blend in with other landscapes in general visible light, such as urine (reindeer are very fond of human urine) and fur, but can be clearly distinguished under ultraviolet light. Reindeer are believed to be the only mammals that can see ultraviolet light, and in the long winter nights of the Arctic, blue eyes can effectively amplify ultraviolet rays, while in the summer polar days, golden eyes can reflect ultraviolet rays to avoid burns.
In addition, reindeer are very resistant to frost. In the polar regions, cold is the number one survival challenge for living things, and although the fur covered by reindeer is light, the cold resistance index is incredibly high, and its minimum temperature threshold is minus 40 °C.
As can be seen from the cross-section of the cut reindeer coated specimen, it consists of two layers of fur, inside and outside. The inner layer is tightly hairy, while the surface layer consists of hollow, long, hard hairs. The long hard hairs containing air are like porous foam, which not only acts as a good heat preservation, but also increases the buoyancy of reindeer swimming.
The porous structure of reindeer fur (Image: Reference 9)
Every year, when temperatures rise in late spring and early summer, reindeer migrate north away from the overwintering taiga. Along the way, they take off their winter hairs to grow summer hairs, and the fluff that falls into the ground just becomes a landmark, and they return from the frozen wasteland in late summer and early autumn.
In the end, the reindeer's ability to stay up late is unmatched. If you think that with your off-road equipment, you can compete with reindeer in terms of hiking, vision, cold protection, etc., then this skill of reindeer will definitely make you unattainable. In the Arctic, human explorers in polar diurnal and polar night environments often experience sleep disturbances. Reindeer, on the other hand, can migrate day and night in this extreme environment, and the key lies in having a "code to stay up late".
This code was recently successfully unraveled by an international team led by Chinese scientists. According to the researchers, due to mutations in the reindeer's core regulatory gene for rhythm pathways (PER2), which makes it unable to bind to another rhythm gene (CRY), the reindeer almost loses the circadian rhythm molecular clock. Reindeer sleeps for very random amounts of time, allowing it to move day and night, further enhancing its survivability in extreme environments.
A herd of reindeer in migration (Image: Baidu Encyclopedia)
Every year in late spring or early autumn, well-equipped reindeer armies begin to migrate. They climbed mountains, stepped on snow, wade through swamps, swam over rivers, day and night, day and night, and fought bravely for the survival and reproduction of the race.
Some herds of reindeer in North America, with annual migration distances of up to 5,000 km and an area of about 1 million m2, are considered to be the mammals with the longest migratory distances. Some populations in northern Europe, which are accustomed to short-distance migration, can walk up to 55 km per day. It can be seen that reindeer are truly the migratory champions of the mammalian kingdom.
<h1 class = "pgc-h-arrow-right" > human reindeer complex</h1>
Since the Neolithic Age, humans have developed a close connection with reindeer. The hunting peoples distributed near the Arctic Circle gradually formed a culture based on the spirit of reindeer. The Evenk Ethnic Township in China's Inner Mongolia Autonomous Region is the southernmost point where reindeer culture reached in Northeast Asia.
Changes in the distribution area of reindeer in China (Source: Reference 11)
The reindeer culture of the Pan-Arctic Circle is a smart way of living created by humans in the alpine Arctic regions that are not suitable for their survival, based on the highly interdependent relationship between man and nature. To date, more than 20 ethnic groups around the world are raising reindeer, with a total of about 250,000 heads.
Reindeer are an important means of transportation (Image: dp.pconline.com.cn)
First of all, reindeer are an important source of subsistence for the peoples of the Arctic Circle. Deer milk provides high calories and nutrients, while deer skins, antlers and deer bones can also be used. Second, reindeer were used as an important means of transportation, and the Tunguska people developed a thriving reindeer transportation industry throughout history. In addition, reindeer is also an important nature worship of reindeer cultural peoples.
Bionic study of some animal skins of reindeer (Image source: Reference 7)
However, since the 21st century, reindeer culture has shown a gradual decline trend. Studies have shown that the decline of reindeer culture is consistent with the rapid melting of the permafrost of the Northern Hemisphere from south to north and the gradual northward progression of human industrialization. When we trace the reindeer in the history books of the earth, we will find that it accurately presents the drastic changes in the geography and climate of the Pan-Arctic Circle, and at the same time witnesses the profound impact of the modernization process on the Peoples of the Arctic Circle.
<h1 class= "pgc-h-arrow-right" > reindeer give human wisdom</h1>
In history, reindeer, as one of mankind's most loyal friends, have paid countless sweat and blood. Today, reindeer come in sleighs laden with "gifts," each of which benefits humans immensely, such as its antlers.
Jeff Biernaskie, a molecular biologist at the University of Calgary in Canada who has worked on the miraculous regenerative power of reindeer antlers, said that wounds on reindeer antlers can be completely healed within a month and will not leave any scars. Newly grown skin is completely normal in color and hair follicle distribution, which is rare in mammals. Bill Nasggi, who is also president of the local firefighters' burn treatment association, hopes to one day discover new ways to treat human burns and trauma in antlers.
Reindeer antlers also have an amazing growth rate, with new antlers growing at the fastest rate of up to 2 cm per day. What intrigued scientists was that such a rapid rate of cell proliferation did not trigger tumors. The study found that the growth of antler tissue must meet two conditions at the same time: the first is to open up a unique cancer-related signaling pathway, and the second is to allow the tumor suppressor gene to be highly expressed. The researchers point out that understanding the mechanism of antler cell proliferation helps us unravel the mystery of human cell carcinogenesis.
Balance between rapid antler regeneration and reduced cancer risk (Image: Reference 9)
Calves can grow antler horns around 10 days after birth, and eventually the antlers can grow up to 135 cm wide. In the extreme environment of the Arctic lack of sunlight, how do reindeer ensure that their bones are not deficient in calcium? Recent findings by an international team led by Chinese scientists have shown that the activity of two key enzymes related to vitamin D (which contributes to the absorption and utilization of calcium) metabolism in reindeer is much higher than that of other animals, ensuring that they maintain a highly efficient metabolism in low light environments and promote the growth of antlers.
Antler regeneration cycle and profile (Image source: Reference 9)
Reindeer have given so much wealth to mankind that all they want is a home where they can survive and reproduce.
Reindeer themselves have a strong ability to survive, and they not only have to resist the extreme climates of the polar alpine regions, but also face hungry predators. Among them, the gray wolf is the largest natural enemy of adult reindeer, and according to statistics, an average of 2-3 days wolf pack (composed of 7-9 wolves) will kill a reindeer. In addition, there are golden eagles, brown bears, wolverines, polar bears, bloodsuckers... But even so, reindeer herds have remained vigorous for thousands of years.
In modern times, however, the global population of reindeer has been declining due to overexploitation of natural resources, habitat encroachment, and climate change that has caused plant growth to be out of sync with reindeer migration. Glenn Yannic, a Canadian population geneticist, genetically predicted the fate of the Reindeer in The next 50 years.
The area suitable for reindeer living in the dark color will shrink sharply (Image source: Reference 10)
During the last glacial period 20,000 years ago, glaciers engulfed the habitats suitable for reindeer at the time and shaped reindeer genes, which may have prevented reindeer from adapting to future climate change. According to the model established by the researchers, as the greenhouse effect intensifies, reindeer may lose 89% of their suitable habitat by 2080. The researchers say he is pessimistic about the future of the reindeer species.
And we should also take action, consciously love wild animals, and not let reindeer disappear from our eyes and become a distant legend of Christmas Eve.
< h1 class="pgc-h-arrow-right" > references:</h1>
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