Low daily energy expenditure enables giant pandas to survive on bamboo

Abstract

Giant pandas (Ailuropoda melanoleuca) belong to the bear family (Urisidae) within the order Carnivora and specialize on a diet of bamboo, but still retain a typical carnivoran gastrointestinal tract. Consequently, they have a very low energy digestive efficiency (9.5%-34%) if fed only bamboo in captivity. The property of metabolic physiology of giant pandas is an interesting question. McNab [1] wrote in his new book Extreme Measures that "basal metabolic rate (BMR) of the giant panda, a semi-arboreal, bamboo-eating bear, has not been measured, but given its habits, it undoubtedly has a BMR that is appreciably less than expected from (body) mass. Its basal rate is possibly similar to, or less than, that found in the sloth bear (Melursus ursinus), which feeds heavily on termites and has a basal rate equal to 80% (of expected). The sloth bear, and presumably the giant panda, differ in energetics from other bears such as omnivorous black (Ursus americanus) and brown bears (Ursus arctos), and strictly carnivorous polar bears". Because of their special position in both conservation and culture, the physiology of giant pandas is no doubt of interest to many animal physiologists. Surprisingly there are no available data about their basal metabolism, although several papers stated their special digestive physiological function, such as the ability to digest fiber [2], but the role of gut microbiota is still unclear. It has been found that the gut microbiota of giant panda and red panda (Ailurus fulgens, also carnivorous but eating bamboo), diverged rather than converged based on the same diet, and the bacterial taxa between giant and red pandas are different [3].Scientists have long speculated that to survive on bamboo, which is such a low quality food, giant pandas should have a low rate of metabolism. It has been reported, by using remote radar technology to get heart rate, which is often closely related to oxygen consumption, that giant pandas might exhibit hypometabolism during sleep for energy conservation. Giant pandas have heart rates lower than captive black bears and brown bears during a time of seasonal lethargy after adjustment for body mass. According to calculated levels of metabolic depression, giant pandas lower metabolism on a daily basis to levels similar to those of black and brown bears during their seasonal lethargy [4]. McNab [5] has measured the basal rate of the red panda and found that their basal rate was equal to 49% of the value expected from mass, which undoubtedly reflects its bamboo diet and possibly its arboreal habits. He estimated the basal rate of giant pandas according to the equation for 62 carnivorans that the expected basal rate is 59% of the value expected from body mass for a giant panda with body mass of 120 kg.Recently in a collaboration between scientists from the Institute of Zoology and the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, and Beijing Zoo, new findings and advances on the energetics and physiology of giant pandas were publis...

Red panda fine‐scale habitat selection along a Central Himalayan longitudinal gradient

“…Apart from bamboo, our study suggests that tree canopy coverage, proximity to water sources and species diversity were critical habitat requirements of red panda distribution, similar to the findings of previous studies (Bhatta et al, ; Bista, Shrestha, Sherpa, et al, ; Dorji, Vernes, & Rajaratnam, ; Pradhan et al, ; Thapa et al, ; Williams, ; Yonzon & Hunter, ). However, red pandas responded to these predictors differently in the three longitudinal complexes, suggesting diverse adaptations to physiological, thermoregulatory, and ecological constraints (Fei, Hou, Spotila, Paladino, & Zhang, ; McNab, ; Wang, ). Tree species richness, tree diameter, canopy cover, and tree height create unique climatic regimes at fine levels (Anhuf & Rollenbeck, ).…”

A single nucleotide mutation in the dual-oxidase 2 (DUOX2) gene causes some of the panda's unique metabolic phenotypes

“…In nature they typically move <500 m daily and spend ∼40% of their time resting [ 6 ]. Moreover, pandas have smaller brains, kidneys and livers compared to other large mammals, which may also contribute to their low metabolic rates [ 7 , 8 ]. In addition, they have low levels of thyroid hormones thyroxine (T4) and triiodothyronine (T3), which average ∼50% and ∼60%, respectively, of that expected for similar-sized mammals [ 8 ].…”

“…Moreover, pandas have smaller brains, kidneys and livers compared to other large mammals, which may also contribute to their low metabolic rates [ 7 , 8 ]. In addition, they have low levels of thyroid hormones thyroxine (T4) and triiodothyronine (T3), which average ∼50% and ∼60%, respectively, of that expected for similar-sized mammals [ 8 ]. These aspects of their unusual metabolic phenotype have been hypothesized to stem from a panda-unique single-nucleotide mutation in the DUOX2 gene [ 7 ], which is absent in other carnivores, mice and humans.…”