ODONTOLOGIA

The giant panda is a terrestrial animal and primarily spends its life roaming and feeding in the bamboo forests of the Qinling Mountains and in the hilly Sichuan Province.[29] Giant pandas are generally solitary,[30] and each adult has a defined territory, and a female is not tolerant of other females in her range. Pandas communicate through vocalization and scent marking such as clawing trees or spraying urine.[8] They are able to climb and take shelter in hollow trees or rock crevices, but do not establish permanent dens. For this reason, pandas do not hibernate, which is similar to other subtropical mammals, and will instead move to elevations with warmer temperatures.[31] Pandas rely primarily on spatial memory rather than visual memory.[32]

Social encounters occur primarily during the brief breeding season in which pandas in proximity to one another will gather.[33] After mating, the male leaves the female alone to raise the cub.[34]

Though the panda is often assumed to be docile, it has been known to attack humans, presumably out of irritation rather than aggression.[35][36][37]

Diet

Pandas eating bamboo.

File:Pandas playing 640x480.ogv

Panda eating, standing, playing

Despite its taxonomic classification as a carnivoran, the giant panda's diet is primarily herbivorous, consisting almost exclusively of bamboo.[27] However, the giant panda still has the digestive system of a carnivore, as well as carnivore-specific genes,[38] and thus derives little energy and little protein from consumption of bamboo. Its ability to digest cellulose is ascribed to the microbes in its gut.[39][40] Pandas are born with sterile intestines, and require bacteria obtained from their mother's feces to digest vegetation.[41][42] The giant panda is a "highly specialized" animal with "unique adaptations", and has lived in bamboo forests for millions of years.[30] The average giant panda eats as much as 9 to 14 kg (20 to 30 lb) of bamboo shoots a day to compensate for its low level of energy digestibility. Ingestion of such a large quantity of material is possible due to the rapid passage of large amounts of indigestible plant material through the short, straight digestive tract.[43][44] It is also noted, however, that such rapid passage of digesta limits the potential of microbial digestion in the gastrointestinal tract,[43] limiting alternative forms of digestion. Given this large diet, the giant panda defecates up to 40 times a day.[45] The limited energy input imposed on it by its diet has affected the panda's behavior. The giant panda tends to limit its social interactions and avoids steeply sloping terrain to limit its energy expenditures.[46]

Two of the panda's most distinctive features, its large size and round face, are adaptations to its bamboo diet. Anthropologist Russell Ciochon observed: “[much] like the vegetarian gorilla, the low body surface area to body volume [of the giant panda] 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.”[46] Similarly, the giant panda's round face is the result of powerful jaw muscles, which attach from the top of the head to the jaw.[46] Large molars crush and grind fibrous plant material.

The morphological characteristics of extinct relatives of the giant panda suggest that while the ancient giant panda was omnivorous 7 mya, it only became herbivorous some 2-2.4 mya with the emergence of A. microta.[47][48] Genome sequencing of the giant panda suggests that the dietary switch could have initiated from the loss of the sole T1R1/T1R3 umami taste receptor, resulting from two frameshift mutations within the T1R1 exons.[49] Umami taste corresponds to high levels of glutamate as found in meat, and may have thus altered the food choice of the giant panda.[50] Although the pseudegenization 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.[48][51][52] The mutation time for the T1R1 gene in the giant panda is estimated to 4.2 mya[48] while fossil evidence indicates bamboo consumption in the giant panda species at least 7 mya,[47] signifying that although complete herbivory occurred around 2 mya, the dietary switch was initiated prior to T1R1 loss-of-function.

Pandas eat any of 25 bamboo species in the wild, such as Fargesia dracocephala[53] and Fargesia rufa.[54] Only a few bamboo species are widespread at the high altitudes pandas now inhabit. Bamboo leaves contain the highest protein levels; stems have less.[55]

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

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