If someone asks what pandas eat, you’d surely answer, “bamboo!” But, do you know what kind of bamboo do they eat? And how much nutrition is contained in bamboos? How do they eat bamboo in their mouth and how is it digested?
1. What do pandas like to eat?
There are 63 types of bamboo in pandas’ food. These bamboos are mainly divided into two families – one is the stenostachyous bamboo (pronounced as ce in 4th tone) and there are 19 kinds of them in the super bamboo family; the other one is the North American arrow bamboo, and there’re 44 kinds of them in the super bamboo family, half of which only exists in China.
The habitat of giant pandas is about 200,000 square kilometers. Among them, coniferous and broad-leaved forests grow mainly, and the mountains are crisscrossed, the mountains and rivers are interspersed, and the temperature is relatively low, so most of the bamboo grown there is cold and temperate.
Although pandas like to eat bamboo, they are not without choice. They like to pick different bamboo species and different parts to eat. Since bamboo is a low-nutrient, high-fiber food, it is difficult to pick the suitable parts to eat.
The main fibrous substances in bamboo are cellulose, hemicellulose and lignin. Hemicellulose is relatively easy to be digested, and cellulose and lignin are more difficult to be digested.
Some giant pandas tend to choose these low cellulose and lignin content, such as bamboo shoots and fresh bamboo leaves. Other pandas would pick bamboos that can be excreted quickly, so that they can continue eating more.
Like humans, pandas also like to eat bamboo shoots, but they don’t like bamboo poles and old leaves. From Spring to Summer, they love to feed on bamboos of the genus Indica and Asparagus, as well as bamboo shoots of Bashan wood bamboo, walking stick bamboo, Fargesia Fargesia, West China Fargesia and Big Fargesia.
Bamboo shoots are unbranched Hsinchu plants that grow from bamboo stalks. They have young tissues, high water content, 1.27% crude fat, 33.62% crude fiber, 10.32% crude protein and 26.15% of total sugar content. The bamboo shoots are young and juicy, have good palatability and are easy to digest and absorb. They are delicious food for pandas.
Every year from Spring to Autumn, in order to eat different types of bamboos and bamboo shoots at different altitudes, the giant panda would migrate from mid to high mountains, such an action is called “catching bamboo shoots.”
However, as bamboo shoots only grow in summer, the pandas mainly eat bamboo leaves and bamboo stalks throughout other times of the year. When there are bamboo shoots, the giant panda would eat vigorously – they would 20 hours a day, and that’s 40 kg in total! Even if they only eat bamboo leaves, you still need to eat about 15 kg.
The bamboo shoots are very delicious for pandas, and they are especially easy to be digested. The bamboo shoots have a layer of skin, so the pandas would peel off the skin and eat only the core.
From October each year to April of the following year, the giant pandas spend most of their time eating bamboo leaves. If there are no fresh bamboo leaves, for example in winter, they would have to eat some bamboo sticks, which are at least better than those old leaves.
In fact, bamboo poles are not utterly useless, at least the micro-element content is relatively high, which is beneficial to supplement these elements in special stages. When eating the bamboo poles, giant pandas like to eat their upper part, and they usually throw away the lower parts directly.
In late spring and early summer, they can start eating fresh and delicious bamboo shoots. After it gets colder in September, the bamboo shoots are gone and they could only eat bamboo leaves and sticks.
When looking at the whole stick of bamboo, the content of nutrients gradually increases from the lower part to the upper part.
Taking cold arrow bamboo as an example, the crude fat content of bamboo pole is 0.59%, it accounts for 3.37% in the branch, the crude protein content of bamboo pole is 4.20%, it’s 19.44% in bamboo leaves; the content of crude fiber of bamboo rod is 46.66%, it’s 24.27% in bamboo leaves.
It can be seen that although pandas prefer bamboo shoots, they often feed on leaves and shoots in the middle and upper parts of young bamboos.
Giant pandas look for food during the day and night, and spend more time at night doing it than during the day. Even so, pandas still need to spend 40% of their time sleeping, and they usually sleep for two or three hours each time.
Giant pandas like taking an afternoon nap. After all, it’s an enjoyable thing to sleep under the sun in the afternoon. When the sun rises and sets, it’d be the best time to eat. They even have to add one more meal after 11pm. What a great life!
For sure, they need to eat with their hands. Pandas don’t use chopsticks, they can only grab food by hand. However, there is one very special thing, each panda has his own favorite hand to eat.
Some pandas like to use their left paws, while some like to use their right paws. Young male pandas like to use their left paws, and old male pandas like to use their right paws. It is said that this is because the right brain of pandas develops faster.
Since pandas have a pseudo thumb similar to a human thumb, they can hold things like humans. Pandas also have five fingers. In addition to the thumb, there are also two knuckles, and the other fingers also have three knuckles. Have you ever seen them eating the bamboo sticks by grabbing them? It looks exactly like you do while you eat.
Pandas have few taste buds on their tongues. It’s probably because they always eat bamboo and it has only one taste only. What’s the use of different taste buds anyway?
Giant pandas have canines, showing that they really are carnivore. Of course, there are also molars, so we can assume them being omnivorous. However, 90% of giant pandas have dental caries. Since there is no sugar in the bamboo, and they have bad tooth probably because the bamboo has worn them out.
Giant pandas just bite bamboo into small pieces and swallow it, they never chew it slowly. And the parts that they bite off are of different lengths.
Therefore, the panda’s esophageal cortex is relatively thick. It may be because the bamboo stubbles might scratch the pandas, their thick esophageal cortex can protect themselves from being scratched or hurt.
Also, they usually have large stomachs and a thick layer of gastric mucosa and gastric muscle layer. These can enable them to adapt to their appetite and the sharp bamboo.
The panda’s intestine is short, which is consistent with the characteristics of a predator. The small intestine is only about one meter, and the large intestine is less than one foot long. And pandas have no cecum, apparently not evolved from a vegetarian diet.
However, although their intestine is short, the panda has evolved other ways to digest bamboo, such as increasing the number and length of intestinal villi and increasing the number of glands.
They can wrap the bamboo with mucus so that the bamboo no longer gets stuck, and they can also wrap the bamboo smoothly into feces. It also improves the ability of intestinal villus repair.
Bamboo stays in the panda’s intestine for 8-12 hours, with the shortest bamboo shoots and the longest bamboo leaves. But it’s worth knowing that food stays in the stomachs of deer and horses for more than a day. In that case, the giant panda’s intestine is relatively straight.
Although giant pandas are not able to digest cellulose, the bacteria in the panda’s intestines can. Pseudomonas in the panda’s intestine secretes laccase, an enzyme that hydrolyzes lignin.
After the lignin is hydrolyzed, cellulose would be exposed from the bamboo. At this time, the cellulase and hemicellulase secreted by Clostridium and Bacillus in the panda’s intestine would begin to work. In fact, you also have this kind of bacteria in the intestines that can decompose cellulose, which we generally call probiotics.
99% of the panda’s poops is undigested bamboo. The more they eat, the more they excrete. And they can excrete up to 20 kg per day! It’s quite stunning! Pandas’ overall digestibility of bamboo is less than 20%. In other words, they excrete most of what they eat. The digestibility of cellulose is even as low as 8%.
Giant pandas living in the wild occasionally eat other plants, such as awnless wheat, corn, equaver, cymbopogon caesius, polyporus tenuiculus, wild angelica, cormorant, young fir bark, and many other plants. Sometimes, they also change their taste a bit and eat corpses of other animals or catch smaller animals for food.