Giant pandas evolved from carnivores, so why do 90% of their food consist of bamboo?

According to media reports, the Chinese people welcomed the giant panda "Ya Ya" who returned from the United States back to Shanghai Pudong International Airport on April 27. The 23-year-old giant panda received bamboo brought by staff as soon as she got off the plane at the airport, which made people full of expectations for her return.

CCTV introduced that in order to quarantine "Ya Ya", Shanghai Zoo has set up a special quarantine site, including indoor animal houses, outdoor playgrounds, feed processing rooms, etc. The indoor animal houses are equipped with air conditioners, and a rich and sufficient amount of bamboo and complementary food are prepared. During the quarantine period, the Beijing Zoo's expert team will be on-site 24 hours a day to accompany "Ya Ya". In view of the special circumstances of "Ya Ya" such as advanced age and changes in living environment, they will carefully carry out feeding care, health monitoring, diagnosis and treatment, etc., to accompany "Ya Ya" through the one-month quarantine period and help her adapt to life in China as soon as possible.

Those who are familiar with pandas know that they spend 19 hours a day eating bamboo. However, in animal classification, giant pandas are not herbivores, but belong to the order Carnivora of the class Mammalia, and are truly members of the carnivore family. So why are giant pandas, who practice vegetarianism, classified as carnivores?

The ancestors of pandas became vegetarians to avoid competition from their peers

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According to the unearthed giant panda fossils, it can be inferred that giant pandas have lived on the earth for 8 million years. Their ancestors were the primitive pandas, which lived in Lufeng and Yuanmou in Yunnan, China. Take the Lufeng primitive pandas for example. More than 8 million years ago, they were carnivores similar in size to foxes. With the advent of the Ice Age, the earth's climate was extremely cold. The primitive pandas, along with many other carnivores, were driven to a very small area by the cold. The edible food decreased, and the competition among "peers" became more intense. Faced with fierce competition, in order to survive, the primitive pandas were forced to choose a survival plan, that is, "changing careers" to become vegetarians.

Although 99% of the giant panda's food is now bamboo, its teeth and digestive tract remain the same. Its canine teeth are still sharp, and its digestive tract is still the structure of a carnivore. Generally speaking, because plant foods have more fiber and are difficult to digest, in order to fully digest and absorb the plants they eat, the digestive tract of herbivores is particularly long. For example, the intestines of deer are about 15 times their body length, and the intestines of sheep are about 25 times their body length. The intestines of carnivores are generally 4 to 8 times their body length. The intestines of giant pandas are just in this range, and their intestines are only 4 to 6 times their body length. Therefore, they are still classified as carnivores.

Bamboo has low nutritional value. How do pandas ensure their energy needs?

Giant pandas have been using the intestines of carnivores to digest bamboos rich in cellulose. This is obviously due to the mismatch between the food they eat and their digestive tract, which results in a very low nutrient absorption rate. In order to ensure the body's energy needs, giant pandas have to eat a lot of bamboo every day. According to statistics, a giant panda needs to eat 20 to 30 kilograms of bamboo every day in spring. Therefore, the giant pandas we see are often holding bamboo in their hands. In a day, giant pandas spend nearly half of their time eating bamboo and the other half of their time sleeping.

According to Xu Xinjie, vice president of the Henan Zoological Society, there are more than 1,300 species of bamboo in the world, nearly 300 species in my country, and more than 20 species that giant pandas can eat. The most popular ones are cold-arrow bamboo, large-arrow bamboo and Chinese-stem bamboo, because these bamboos have a light sweet taste. The next favorites are walking stick bamboo, pine bamboo, wood bamboo, golden bamboo, etc., and they mainly eat these 1-2 year old young bamboos. In addition, giant pandas also eat some plants and wild fruits, such as grain crops, young fir bark, angelica dahurica stalks, grasses of the Gramineae family, and hazelnuts, kiwis, aggregate fruits, loquats, silk chestnuts, etc.

Pandas also have their own preferences for bamboo

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An article published in the Journal of the International Society for Microbial Ecology by Zhang Wenping, a researcher at the Chengdu Research Base of Giant Panda Breeding, revealed the reason why giant pandas choose bamboo as their main food: compared with other foods in the wild, bamboo is widely distributed, easy to obtain, and there are fewer competitors for food with giant pandas; compared with other woody plants, bamboo contains a relatively high concentration of starch; the starch content of different parts of bamboo changes with the seasons, and giant pandas always choose to eat parts of bamboo with high starch content.

"The bamboo shoots have the highest starch and hemicellulose content. Bamboo grows very fast, with two seasons every year. The season when bamboo shoots grow is also the season when giant pandas are in heat and give birth to their offspring. In this season, giant pandas give priority to eating bamboo shoots." Zhang Wenping said that the high starch and hemicellulose content in bamboo shoots can replenish the giant pandas' physical strength and increase their weight when they are in heat and giving birth to their offspring. In winter, when there are no bamboo shoots and tender bamboo leaves, the starch and soluble sugar content in bamboo stalks will reach the highest point of the year, and then the giant pandas will start to eat bamboo stalks.