Giant panda
The giant panda, also known as the panda bear or simply panda, is a bear species endemic to China. It is characterised by its white coat with black patches around the eyes, ears, legs and shoulders. Its body is rotund; adult individuals weigh and are typically long. It is sexually dimorphic, with males being typically 10 to 20% larger than females. A thumb is visible on its forepaw, which helps in holding bamboo in place for feeding. It has large molar teeth and expanded temporal fossa to meet its dietary requirements. It can digest starch and is mostly herbivorous with a diet consisting almost entirely of bamboo and bamboo shoots.
The giant panda lives exclusively in six montane regions in a few Chinese provinces at elevations of up to. It is solitary and gathers only in mating seasons. It relies on olfactory communication to communicate and uses scent marks as chemical cues and on landmarks like rocks or trees. Females rear cubs for an average of 18 to 24 months. The oldest known giant panda was 38 years old.
As a result of farming, deforestation and infrastructural development, the giant panda has been driven out of the lowland areas where it once lived. The Fourth National Survey, published in 2015, estimated that the wild population of giant pandas aged over 1.5 years had increased to 1,864 individuals; based on this number, and using the available estimated percentage of cubs in the population, the IUCN estimated the total number of Pandas to be approximately 2,060. Since 2016, it has been listed as Vulnerable on the IUCN Red List. In July 2021, Chinese authorities also classified the giant panda as vulnerable. It is a conservation-reliant species. By 2007, the captive population comprised 239 giant pandas in China and another 27 outside the country. It has often served as China's national symbol, appeared on Chinese Gold Panda coins since 1982 and as one of the five Fuwa mascots of the 2008 Summer Olympics held in Beijing.
Etymology
The word panda was borrowed into English from French, but no conclusive explanation of the origin of the French word panda has been found. The closest candidate is the Nepali word ponya, possibly referring to the adapted wrist bone of the red panda, which is native to Nepal. In many older sources, the name "panda" or "common panda" refers to the red panda, which was described some 40 years earlier and over that period was the only animal known as a panda. The binomial name Ailuropoda melanoleuca means black and white cat-foot.Since the earliest collection of Chinese writings, the Chinese language has given the bear many different names, including mò, huāxióng and zhúxióng. The most popular names in China today are dàxióngmāo, or simply xióngmāo. As with the word panda in English, xióngmāo was originally used to describe just the red panda, but dàxióngmāo and xiǎoxióngmāo were coined to differentiate between the species.
In Taiwan, another popular name for panda is the inverted dàmāoxióng, though many encyclopedias and dictionaries in Taiwan still use the "bear cat" form as the correct name. Some linguists argue, in this construction, "bear" instead of "cat" is the base noun, making the name more grammatically and logically correct, which have led to the popular choice despite official writings. This name did not gain its popularity until 1988, when a private zoo in Tainan painted a sun bear black and white and created the Tainan fake panda incident.
Taxonomy
For many decades, the precise taxonomic classification of the giant panda was under debate because it shares characteristics with both bears and raccoons. In 1985, molecular studies indicated that the giant panda is a true bear, part of the family Ursidae. These studies show it diverged about from the common ancestor of the Ursidae; it is the most basal member of this family and equidistant from all other extant bear species.Subspecies
Two subspecies of giant panda have been recognized on the basis of distinct cranial measurements, colour patterns, and population genetics.- The nominate subspecies, A. m. melanoleuca, consists of most extant populations of the giant panda. These animals are principally found in Sichuan and display the typical stark black and white contrasting colours.
- The Qinling panda, A. m. qinlingensis, is restricted to the Qinling Mountains in Shaanxi at elevations of. The typical black and white pattern of Sichuan giant pandas is replaced with a light brown and white pattern. The skull of A. m. qinlingensis is smaller than its relatives, and it has larger molars.
Phylogeny
Of the eight extant species in the bear family Ursidae, the giant panda's lineage branched off the earliest.Distribution and habitat
The giant panda is endemic to China. It is found in small, fragmented populations in six mountainous regions in the country, mainly in Sichuan, and also in neighbouring Shaanxi and Gansu. Successful habitat preservation has seen a rise in panda numbers, though loss of habitat due to human activities remains its biggest threat. In areas with a high concentration of medium-to-large-sized mammalssuch as domestic cattle, a species known to degrade the landscapethe giant panda population is generally low. This is mainly attributed to the panda's avoidance of interspecific competition.The species has been located at elevations of above sea level. They frequent habitats with a healthy concentration of bamboos, typically old-growth forests, but may also venture into secondary forest habitats. The Daxiangling Mountain population inhabits both coniferous and broadleaf forests. Additionally, the Qinling population often selects evergreen broadleaf and conifer forests, while pandas in the Qionglai mountainous region exclusively select upland conifer forests. The remaining two populations, namely those occurring in the Liangshan and Xiaoxiangling mountains, predominantly occur in broadleaf evergreen and conifer forests.
Giant pandas once roamed across Southeast Asia from Myanmar to northern Vietnam. Their range in China spanned much of the southeast region. By the Pleistocene, climate change affected panda populations, and the subsequent domination of modern humans led to large-scale habitat loss. Subfossil remains from sinkholes suggest that they still inhabited the Gaoligong Mountains of Yunnan Province, on the border between China and Myanmar, as recently as 5,000 years ago. This area suffered heavy deforestation around the time of the early Ming Dynasty, which may have been the event that extirpated pandas from the area. In 2001, it was estimated that the range of the giant panda had declined by about 99% of its range in earlier millenniums.
Description
The giant panda has a body shape typical of bears. It has black fur on its ears, limbs, shoulders and around the eyes. The rest of the animal's coat is white. The giant panda's distinctive coloration appears to serve as camouflage in both winter and summer environments as they do not hibernate. The white areas serve as camouflage in snow, while the black shoulders and legs conceal them in shade. Studies in the wild have found that when viewed from a distance, the panda displays disruptive coloration, while up close, they rely more on blending in. The black ears may be used to display aggression, while the eye patches might facilitate them identifying one another. The giant panda's thick, woolly coat keeps it warm in the cool forests of its habitat.The panda's skull shape is typical of durophagous carnivorans. It has evolved from previous ancestors to exhibit larger molars with increased complexity and expanded temporal fossa. A study revealed that a giant panda had a bite force of 1298.9 Newton at canine teeth and 1815.9 Newton at carnassial teeth. Finite element analysis has found that pandas have the highest bite force relative to their body size among ursids. The giant panda has the largest masticatory muscles among bears, being more than twice as large as those of the American black bear with an equivalent brain weight; digastric muscle is equal to 30% of brain weight in giant panda compared to 10% in black bear.
Adults measure around long, including a tail of about and tall at the shoulder. Males can weigh up to. Females are generally 10–20% smaller than males. They weigh between and. The average weight for adults is.
The giant panda's paw has a digit similar to a thumb and five fingers; the thumb-like digit is actually a modified sesamoid bone that helps it to hold bamboo while eating. The evolution of the panda's pseudo-thumb may have occurred because the first digit of its forepaws, equivalent to the thumb in primates, is not opposable and is aligned with the rest of the digits. The giant panda's tail, measuring, is the second-longest in the bear family after the sloth bear.
Ecology
Diet
Despite its taxonomic classification as a carnivoran, the giant panda's diet is primarily herbivorous, with approximately 99% of its diet consisting of bamboo. However, the giant panda still has the digestive system of a carnivore, as well as carnivore-specific genes, and thus derives little energy and little protein from the consumption of bamboo. The ability to break down cellulose and lignin is very weak, and their main source of nutrients comes from starch and hemicelluloses. The most important part of their bamboo diet is the shoots, that are rich in starch and have up to 32% protein content. Accordingly, pandas have evolved a higher capability to digest starches than strict carnivores. Raw bamboo is toxic, containing cyanide compounds. Pandas' body tissues are less able than herbivores to detoxify cyanide, but their gut microbiomes are significantly enriched in putative genes coding for enzymes related to cyanide degradation, suggesting that they have cyanide-digesting gut microbes. It has been estimated that an adult panda absorbs of cyanide a day through its diet. To prevent poisoning, they have evolved anti-toxic mechanisms to protect themselves. About 80% of the cyanide is metabolized to less toxic thiocyanate and discharged in urine, while the remaining 20% is detoxified by other minor pathways.During the shoot season from April to August, the giant panda stores a large amount of food in preparation for the months succeeding this seasonal period, in which it lives off a diet of bamboo leaves.
The average giant panda eats of bamboo shoots per day to compensate for the limited energy content of its diet. Ingestion of such a large quantity of material is possible and necessary because of the rapid passage of large amounts of indigestible plant material through the short, straight digestive tract. Such rapid passage of digesta limits the potential of microbial digestion in the gastrointestinal tract, limiting alternative forms of digestion. Given this voluminous diet, the giant panda defecates up to 40 times a day.
The limited energy input imposed on it by its diet has affected the giant panda's behaviour. It tends to limit its social interactions and avoids steeply sloping terrain to limit its energy expenditures. Their field metabolic rate, the amount of energy used by an animal in its daily life, is one of the lowest reported among mammals, comparable to that of sloths.
Two of the panda's most distinctive features, its large size and round face, are adaptations to its bamboo diet. Anthropologist Russell Ciochon observed: " like the vegetarian gorilla, the low body surface area to body volume is indicative of a lower metabolic rate. This lower metabolic rate and a more sedentary lifestyle allows the giant panda to subsist on nutrient poor resources such as bamboo." The giant panda's round face is the result of powerful jaw muscles, which attach from the top of the head to the jaw. Large molars crush and grind fibrous plant material.
The enzyme alanine—glyoxylate transaminase is also expressed in the peroxisome of giant panda cells instead of only in the mitochondria like carnivorous mammals, which would enable glyoxylate to be metabolised from glycolate in plant matter. Proteins make up 50% of the macronutrients absorbed, similar to proportion of carnivorous mammals at 52–54%; the nutritional contribution of protein from bamboo is 61% when only the leaves and shoots are considered, and 48% when the digestible parts of cellulose and hemicellulose are included. This indicates that the transition to herbivory was not as extreme in this species as it might appear.
The morphological characteristics of extinct relatives of the giant panda suggest that while the ancient giant panda was omnivorous 7 million years ago, it only became herbivorous some 2–2.4 mya with the emergence of A. microta. Genome sequencing of the giant panda suggests that the dietary switch could have initiated from the loss of the sole umami taste receptor, encoded by the genes TAS1R1 and TAS1R3, resulting from two frameshift mutations within the T1R1 exons. Umami taste corresponds to high levels of glutamate as found in meat and may have thus altered the food choice of the giant panda. Although the pseudogenisation of the umami taste receptor in Ailuropoda coincides with the dietary switch to herbivory, it is likely a result of, and not the reason for, the dietary change. The mutation time for the T1R1 gene in the giant panda is estimated to 4.2 mya while fossil evidence indicates bamboo consumption in the giant panda species at least 7 mya, signifying that although complete herbivory occurred around 2 mya, the dietary switch was initiated prior to T1R1 loss-of-function.
Giant pandas eat any of 25 bamboo species in the wild, with the most common including Fargesia dracocephala and Fargesia rufa. Only a few bamboo species are widespread at the high altitudes pandas now inhabit. Bamboo leaves contain the highest protein levels; stems have less. Because of the synchronous flowering, death, and regeneration of all bamboo within a species, the giant panda must have at least two different species available in its range to avoid starvation. While primarily herbivorous, the giant panda still retains decidedly ursine teeth and will eat meat, fish, and eggs when available. In captivity, zoos typically maintain the giant panda's bamboo diet, though some will provide specially formulated biscuits or other dietary supplements.
Giant pandas will travel between different habitats if they need to, so they can get the nutrients that they need and to balance their diet for reproduction.