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Giant pandas (Ailuropoda melanoleuca) feed almost exclusively on highly fibrous bamboos, but they carry a mixture of herbivorous and carnivorous traits. A new study published in the journal Current biology shows that the macronutrient composition of the diet of giant pandas is similar to that of carnivorous diets and differs from that of herbivorous diets. This may explain why pandas have not fully adapted to the plant diet and suggests that their passage to herbivory has been easier than it seems otherwise.
A giant panda named Xiao Liwu at the San Diego Zoo, California, USA. Image Credit: Sci-News.com.
"This study demonstrates the importance of taking foods and nutrients into account to understand the evolutionary ecology of animals – this is exactly what nutritional geometry is designed for," said Professor David Raubenheimer of the University of Toronto. Sydney, lead author of the study.
Professor Raubenheimer and his colleagues at the University of Sydney and the Chinese Academy of Sciences have used nutritional geometry – an approach taking into account the influence of nutrient and other mixtures. dietary components on health and disease, rather than focusing on a single nutrient isolated – to evaluate macronutrient mixture of the diet of the giant panda.
They discovered that the protein and carbohydrate content of the giant pandas-like diet resembled more like that of a hypercarnivore – animals whose feed comes to more than 70% from others. animals.
With about 50% of its protein energy, the diet of the giant panda resembles that recorded for wild cats (52%) and wolves (54%). The macronutrient composition of panda milk was similar to that of other carnivores.
"According to what they eat, giant pandas belong absolutely to herbivores – but considering the macronutrient composition of diets ingested and absorbed, they could also belong to carnivores," said Dr. Fuwen Wei , lead author of the study, researcher at the Chinese Academy of Sciences.
Giant pandas have developed herbivorous traits, including a skull, jaw-like musculature and teeth adapted to fibrous diets, and a pseudo-thumb used to manipulate bamboo. They also lost the ability to taste umami, which is often associated with meat consumption.
However, giant pandas also have a digestive tract, digestive enzymes and intestinal microbes that resemble those of carnivores and not herbivores. This suggests that a minimal evolutionary change from their ancestral state was required to manage the macronutrient properties of bamboo.
"Our findings can help solve long-standing questions about the evolution of the giant panda, including the unusual transition from carnivorous to an extremely specialized herbivore," the scientists said.
"In fact, the transition was probably more superficial than expected, combining a substantial adaptation to new types of foods with relatively less significant changes in macronutrient management."
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Yonggang Nie et al. Giant pandas are macronutritional carnivores. Current biology, published online May 2, 2019; doi: 10.1016 / j.cub.2019.03.067
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