Why are giant pandas considered national treasures?

Today we are going to talk specifically about our national treasure, the giant panda (Ailuropoda melanoleuca).

Although it is a bear, the key to its name is "cat"; although it is a carnivorous beast, 99% of its food is bamboo. They have gained popularity and love in zoos, but many people forget that their true home is in the mountains and forests . There are less than 2,000 wild pandas living in China, the only one in the world .

Panda cub | Li Binbin

The panda's snout (nose bridge) is obviously shorter than that of other bears. Combined with its broad cheeks and big round head, it is really likable compared to the pointed snout, monkey-like face and hooked nose. It also has two figure-eight-shaped dark circles under its eyes, which make its eyes look ten times bigger. If it were an inverted figure-eight shape, it would not attract so much love.

Short nose, round face, big head, big "eyes", these are the characteristics of babies (cubs), which can stimulate our instinct to protect cubs. Add to that the rolling and wobbling way they walk and the ability to hold bamboo and eat it like a human, and few people can resist the cuteness of pandas.

Panda eats innocently | AAAS

Pandas are cute, but cuteness is not enough to justify spending a lot of money and resources to protect a species. Are pandas destined to become extinct? Is it a waste for us to put so many resources into protecting this species? What role do you and I play in their future?

History of Pandas

Pandas are bears. About 20 million years ago, they first separated from other bear species and evolved independently. In the Miocene period 8 million years ago, the proto-panda (A. lufengensis) came on the stage. They were omnivores , and only their premolars showed the rudiments of eating bamboo.

3 million years ago, the original panda became extinct, but its offshoot, the small panda (A. microta), appeared in south-central China. It is only half the size of today's giant panda, so it is called "small". The small panda is still omnivorous, but the proportion of bamboo in its food is already very high .

Another branch of the primitive panda - Ge's suburban panda | Photo taken by hannah at the Fengtongzhai Nature Reserve Museum

In the middle of the Pleistocene, the Yunnan-Guizhou Plateau and the Qinling Mountains rose up, blocking the dry and cold monsoon from the northwest, creating a hot and humid climate in Yunnan-Guizhou and the southeast of the Qinling Mountains. Later, the small species of giant panda became extinct and was replaced by the Ba's giant panda. Its distribution reached its peak, from Zhoukoudian in the north to Myanmar and Vietnam in the south . During this period, the giant pandas lived with the famous saber-toothed elephants, saber-toothed tigers, Peking Man, and Australopithecus. However, as the temperature dropped during the ice age and the natural environment changed dramatically, most species in the giant panda-saber-toothed elephant fauna could not escape the fate of extinction.

However, humans and pandas have survived to this day. It's just that one species has expanded wildly, while the other has been forced into a dangerous path. The reason is not that they have entered an evolutionary dead end, but because of humans .

Why do pandas choose to eat bamboo?

Many people say that giant pandas should live on meat. Even if they don't eat meat exclusively, they should eat a mixture of high-energy foods such as fruits, honey, and nuts, like black bears, and catch some small animals to fill their teeth. But giant pandas choose to be vegetarians, and they choose bamboo, which is the most difficult plant to swallow and has low nutrition . In essence, bamboo is a piece of woody grass (monocotyledonous grass family), and more than 90% of its dry weight is lignin, cellulose, and hemicellulose. Cellulose and hemicellulose account for up to 65%. In addition, it contains a lot of silicon. It can be said that it is prickly, hard, and has no nutrition. Eating it is like eating squeezed sugarcane residue .

The panda's main food seems to be particularly unpalatable | Chi / flickr

Although bamboo is not tasty, it is widely distributed and in huge quantities. Other animals do not eat it, and hiding in bamboo forests can also avoid large animals such as saber-toothed tigers. In addition, studies have shown that due to gene mutation (Tas1r1 pseudogene), pandas lost their umami receptors 4.2 million years ago, which means that meat is tasteless to pandas . However, it is difficult to give a definite answer as to whether they lost their umami taste first or started eating bamboo first.

We can speculate why pandas eat bamboo, but it is difficult to disprove it . However, if we think about it carefully, no matter what hypothesis is proposed, this huge change in diet has helped pandas reduce direct competition with other species to a large extent and obtain sufficient food, which is a wise move. It can be said that pandas are not a failure in the history of evolution, but a cunning winner .

Panda's weapons

Although their diet has shifted to bamboo, the panda's digestive system still retains the characteristics of a carnivore . For example, their digestive tract is very short, which cannot prolong the retention and digestion time of food; they only have a single stomach and cannot fully absorb nutrients from plants like ruminants (cows and sheep) with four stomach cavities.

Pandas do not have enzymes that can decompose cellulose and lignin, and it is not yet clear whether there are microorganisms in their digestive tracts that can decompose these substances. However, food only stays in the panda's digestive tract for 5 to 13 hours, which is much shorter than other herbivores. Even if there are such microorganisms in its digestive tract, their effect time is also very limited.

Qinling Mountains, pandas eating bamboo | Li Binbin

However, pandas are not sad fat people. They rely on brute force to evolve many magical weapons . Since the food is poor in nutrition and difficult to decompose and absorb, they just eat it efficiently and labor-savingly.

The sesamoid bones in the panda's wrist are specialized into the sixth finger "pseudo-thumb" . It enables pandas to have a gripping function that other bears do not have, allowing them to grasp better, perform more delicate operations, and eat bamboo flexibly and in one go. This gripping ability is not common , except for koalas, North American opossums (toes) and most primates, and the giant and red pandas that eat bamboo. Among them, only the giant and red pandas have specialized "sixth fingers" to grip with the other five fingers. The giant and red pandas are not closely related, but in order to adapt to eating bamboo, they have evolved the same characteristics, which is the so-called " convergent evolution ."

The pseudo-thumb is the pad of flesh near the panda's right eye. There is no claw on this "finger". The panda does not have a sixth finger on its back paw. If you have the opportunity to see the front paw prints of a panda, there will be six finger prints and five claw prints | Thibaud Despres / animalli.com

Compared with other bears, the panda's bite force is second only to polar bears and brown bears. It has strong chewing muscles and a heavy and thick skull, which provides structural support for its strong bite force (there is a reason for its big face). Eating bamboo is like chewing a cucumber, biting it off neatly without any dragging. This smooth bite mark is one of the signs for identifying pandas in the wild . So, don't touch a panda casually, be careful that it grabs your hand and bites you...

The "pseudo-thumb" allows pandas to hold hands. And by the way, let's see how good their teeth are | Dong Lei

Giant pandas eat bamboo wisely

Pandas also increase the number and length of intestinal villi to increase the surface area for absorbing substances . At the same time, their intestinal secretions increase to protect the intestines from being pierced by bamboo with a high silicon content; these secretions are also wrapped around the feces to help the feces pass smoothly . Some of the cells scraped from the feces made it possible for researchers to extract DNA from panda feces - using this DNA information, we can carry out related work on individual panda identification.

Panda poo, from which researchers can extract panda DNA. The color varies depending on whether it ate bamboo leaves or bamboo stalks | WWF-UK

Pandas are not only efficient eaters, but also very patient. Wild pandas spend more than half of their time (10 to 14 hours) eating, and most of the rest of the time is spent sleeping. The daily food intake can reach 12 to 40 kilograms (depending on which part is eaten), which is close to 20 to 40% of their body weight. However, because bamboo has little nutrition and water, most of it is excreted, so in the wild where pandas are distributed, their feces are very noticeable - spindle-shaped, with bamboo poles and leaves clearly identifiable, no odor, and it tastes like green tea when thrown into alcohol. Whether eating or sleeping, pandas cannot stop pooping.

Pandas eat bamboo, and they are also very smart . Bamboo shoots are the most nutritious, so starting from early spring, pandas will chase bamboo shoots all the way from low altitude to high altitude. In summer, bamboo leaves are the most nutritious, so they eat them. In winter, the nutrients go to bamboo poles, so pandas eat the hard stuff. Therefore, pandas can be distributed from the valleys to the upper limit of bamboo altitude of about 3,500 meters, and rely on seasonal vertical migration to meet their nutritional needs .

Is it true that pandas cannot reproduce?

The breeding time of giant pandas is also related to the growth rhythm of bamboo . March to May, when springtime is in full swing, is the mating season for pandas. Although females are only in estrus for two or three days and males have short penises, this does not hinder the strong sexual desire and reproduction of pandas in the wild. Females can mate with multiple males during their short estrus period, and males will look for females in estrus everywhere. As long as they can beat other competitors, they can reproduce everywhere. Pandas reach sexual maturity at the age of 4 to 5 years old. As long as they are not raising cubs, all individuals will participate in reproduction and cannot be stopped. After mating, they return to their own solitary lives, do not interfere with each other, and will not raise the next generation together. This sexually open mating method of multiple females and multiple males is not "sexually cold" at all.

Image | Reuters

Pandas reproduce every two to three years, with one to two litters each time. They will choose to raise the stronger babies, with a survival rate of 60 to 90%. This reproduction rate is not bad at all among higher animals. Those who say that pandas cannot give birth are simply misled by the news about captive conditions .

Pandas like to climb trees, hug trees and rest in trees. Panda cubs tend to stay in trees for a long time to avoid predators | Li Binbin

Pandas give birth nearly half a year after mating, but their eggs remain dormant after fertilization , floating in the uterus until certain conditions are met, when they land on the uterine wall and begin to develop. This is delayed implantation in bears. For pandas, intrauterine development takes less than two months, so the cubs they give birth to weigh only one-third of a can of cola. Some researchers suspect that the condition for fertilized eggs to implant is that the mother switches from eating bamboo shoots to eating bamboo leaves rich in calcium.

Panda mother: It was quite sudden... (note the size of the cub) | panda

After birth, the offspring will cling to their mothers for milk like a follower, and will not start eating bamboo until they are nine months old. This is the spring in April and May, when the flowers are blooming and fresh bamboo shoots rich in protein are emerging. This reproduction cycle is just right for the next generation to catch up with the best season .

Romantically speaking, maternal love is great; the rational explanation is that parents who do not do this will most likely have children who die prematurely, and this branch of the family will be gone, leaving only individuals who can make full use of the food growth cycle.

I won't be stumped by the flowering bamboo.

Pandas only eat bamboo, so once the bamboo blooms, they will all die? Bamboo does have a periodic collective flowering phenomenon, and then die in large numbers. However, there are nearly 40 species of bamboo distributed in the panda habitat that can be eaten by pandas, and the collective flowering cycles of bamboo are different . When one species blooms, the pandas will migrate to other places to find another type of bamboo to eat.

There are many types of bamboo that pandas can eat, such as wood bamboo (left) and arrow bamboo (right) | plantphoto.cn

Pandas are highly myopic , but in the dense bamboo forest under the forest, no matter how good your eyesight is, it is useless. Even if there is a fairy a few meters away, you can't see it. Pandas have an excellent sense of smell . Before you see it, it can smell that you are not the same species. Its first reaction will be to avoid it and walk away silently.

They also use scent marking to distinguish territory and convey courtship signals. When their tails are raised, they mark tree trunks with secretions from the perianal glands mixed with urine. Look carefully at the tail! Although it is less than 20 cm, it is still the longest tail among bears except for the sloth bear . And no matter how dirty it is, it is white , not black!

Hmm, the panda's tail in Kung Fu Panda is drawn wrong | Kung Fu Panda

This is the right way! Drawing | Wing Wolf Elang

Pandas are opportunists, and although they rarely take the initiative to prey on other animals, they will not refuse food that comes easily, such as a rotten corpse lying on the ground . So the 1% other than the 99% bamboo can be meat, fruit, grass or anything else that can be eaten.

Still not optimistic about the future

Tasty and edible bamboo requires the protection of forests. Without shade, bamboo will grow too dense and thick. At the same time, less disturbed forests often have large trees that can provide the pandas need to lay their cubs. This is why a good forest is so important to pandas.

Panda habitat in Wanglang National Nature Reserve, healthy bamboo forest under spruce and fir trees | Li Binbin

Looking up, you can see towering trees; looking down, you can see clumps of green bamboos, lichens hanging from branches, dense mosses, and gentle streams flowing by. This is the paradise of pandas. The peaceful pandas could have lived in this peaceful way with their unique choices , but the sound of deforestation rang out, roads passed through the forests, bulldozers pushed away the shelters, and brought the marks of the city. Hydropower, minerals, farmland, grazing, and even commercial tourism development, uncontrolled traffic of people and vehicles, are all squeezing the wild habitat of pandas step by step, breaking the whole into pieces and "defeating them one by one . "

According to the latest national panda survey, there are 1,864 giant pandas in the wild , distributed in only six mountain ranges in Sichuan, Shaanxi and Gansu provinces: Qinling, Minshan, Qionglai, Daxiang, Xiaoxiang and Liangshan. The total area is 1.6 times the size of Beijing. Among them, Sichuan Minshan, where Jiuzhaigou is located, has the most pandas (40% of the population) and habitat (38%).

The historical distribution (yellow) and current distribution (red) of the panda | untamedscience.com

Although the number of pandas has increased in the past few years, they are divided into 33 local populations, 18 of which have less than 10 individuals and are at high risk of local extinction . They are isolated from other local populations by natural or man-made barriers, making it difficult for individuals and genes to exchange.

If a bamboo blooms and dies, another type of green bamboo may be nearby, but there is no ecological corridor connecting the two areas, so the pandas cannot pass through; if a disease strikes, the local populations are too similar, and it is difficult for individuals to survive with disease-resistant genes, and the result may be the annihilation of a local population. In the current era of rapid climate change, the growth pattern and range of bamboo have changed. Will the giant pandas have time to migrate and adapt? Are their prospects optimistic?

We couldn't relax.

Protecting pandas does more than just protect pandas

As the only country with wild giant pandas, our protection should not stop at expanding the captive population . A more reasonable approach is to invest resources in protecting wild habitats . This kind of protection not only protects pandas, but also protects the lifeline of other creatures.

Pandas don’t just live in enclosures, but also in the mountains. Pictured is the panda Huanhuan | Conserve

The distribution areas of pandas also happen to be the areas with the highest density of species endemic to China. 96% of panda habitats are hotspots for the distribution of species endemic to China (species endemic to China are creatures that you cannot find outside of China).

There are more than 8,000 species of plants and animals in the panda habitat, including 70% of China's unique mammals that live only in forests, 70% of China's unique birds, and 30% of China's unique amphibians. It can be said that protecting any forest that pandas like will protect many unknown, unique and very likely endangered species.

Nearly one-third of the country’s shared hotspots for mammals, birds, and amphibians are located within panda habitats | Li et al. (2016)

You may find it hard to find these species lovable, you may be hard to donate to them, you may be hard to know their existence or even remember their names, and no one may care about their disappearance. However, for a healthy ecosystem, a vibrant forest, the symbol of this land is these species and the intricate relationships between them that we know or don’t know.

I don't know if we are too lucky, but in the southwestern mountains of China, a biodiversity hotspot that is even important to the world, there is a star species that people all over the world pay attention to, the panda. It is precisely because of this attention that this place is already a lucky piece of land compared to other parts of China.

Because of the establishment of panda reserves, these areas still retain intact virgin forests | Li Binbin, at Wanglang National Nature Reserve in Sichuan

There are now 67 protected areas for pandas, protecting 54% of their habitat. Our love for pandas and our protection of their homeland make pandas like a big umbrella. If there is a reasonable and comprehensive protection policy, all creatures living on the same land as giant pandas can be protected.

However, nearly half of panda habitats are still outside protected areas, and this is also the distribution area of ​​other endemic and endangered species. Protecting these places, whether in protected areas, future national parks, protected communities or other new protection models, can be a win-win situation. At the same time, the fragmented habitats of pandas also need to be expanded through habitat restoration and the establishment of corridors to connect populations on isolated islands.

Protecting pandas is not just about protecting individuals, but more about protecting their habitats and the entire ecosystem . This inevitably requires a balance between pandas and humans. Many times we forget that humans are also part of this system . A long time ago, we were technologically backward and had a sparse population. Although we had the desire to conquer, we had a sense of awe for nature. Now, relying on technology, we think we are free from dependence, and we have taken drastic measures, pushing the delicate balance to one end.

Pingwu, Sichuan, dead bamboos eaten by cattle and horses in the panda habitat | Li Binbin

We in the city can easily say that we can solve the problem, but the demand for natural resources is driving changes in the mountains : building more roads and houses, removing river sand and blasting mountains, so that it is convenient for the endless stream of self-driving buses to bring tourists there; the love of meat and the need for development drive the locals to graze cattle, horses and sheep under the forest and eat bamboo saplings; the demand for the replacement of mobile phones, computers and other electronic devices drives the mining of huge mines and the destruction of mountains and forests. All of this is related to you .

We are still waving the panda flag vigorously because we know that it carries not only the fate of the panda species, but also the future of millions of lives on this land.

Leopard cats in Wanglang Nature Reserve | Shao Liangkun

We love pandas, so are we willing to pay more attention to their wild homes and make substantial changes? Are you willing to use your choices and your support for product prices to encourage local people to change their livelihoods, so that they can find reasons and motivation to protect forests from market support? Are you willing to control your desire for excessive consumption and buy a little more space for pandas and other creatures?

Image | ShutterPulp/flickr

Love starts from pandas, but it doesn’t stop at pandas.

Author: Li Binbin

This article comes from the Species Calendar, welcome to forward

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