The image of the panda bear ( Ailuropoda melanoleuca ) is always linked to that of its favorite food: bamboo. This animal is a highly specialized herbivore that feeds almost exclusively on this high-fiber plant, despite the fact that it is descended from primarily carnivorous animals.
This question has always puzzled evolutionary scholars: How did such a big jump in eating habits come about? Added to this is the fact that panda bears retain a curious mixture of characters: on the one hand, they have developed herbivorous traits, which include the skull, jaw muscles and teeth adapted for fibrous diets , as well as a ‘ pseudo-thumb ‘that they use to manipulate bamboo. They have also lost the ability to perceive umami, a flavor closely associated with the carnivorous diet.
But on the other hand, giant pandas also have a digestive tract with enzymes and gut microbes that are more like those of carnivorous animals. In addition, a work published ten years ago in the journal Nature also indicated that the panda would have all the necessary genes to be a carnivore.
The key is in the nutrients
A new study published in the journal Current Biology suggests that the switch to a restricted vegetarian diet did not entail the evolutionary leap one would expect, and that the mixture of herbivore and carnivore characters observed in this endearing animal also has its logic.
The researchers, from the University of Sydney (Australia) and the Chinese Academy of Sciences used an approach that, rather than focusing on the animal’s food source, explores the amounts of macronutrients in its diet.
The results revealed that, although the panda’s diet is based exclusively on plants, due to its protein and carbohydrate content it is more similar to that of super carnivores (species that obtain more than 70% of their diet from other animals ). In the panda, 50% of the energy intake comes in the form of protein , which equates its diet to that of wolves or wild cats. Furthermore, the composition of their breast milk is also similar to that of other carnivores.
“If we look at what they eat, pandas are herbivores, but if we did not know what their food source is and analyzed only the composition of the macronutrients they absorb to deduce it, we could be wrong and say that they are carnivores”, explains Fuwen Wei, one of the study participants.
These findings appear to help answer questions about the evolutionary history of the panda, including that unusual transition from carnivorous ancestry to highly specialized herbivore. “In fact, the transition was probably more superficial than previously assumed , combining substantial adaptation to new types of food with relatively smaller changes in macronutrient management,” the authors write in the work. These types of changes would include, for example, selecting the parts of the bamboo with the lowest fiber content.
The team will continue to study the evolution and adaptation of the giant panda, and hope that the results of their research can help conserve this endangered species.
Reference: Giant Pandas Are Macronutritional Carnivores. Nie et al., 2019, Current Biology29, 1–6
