Pandas are famous for being fussy eaters, but a new study says there is method to their madness, with the animals switching between different species and parts of bamboo plants to maintain a balanced diet and reproduce.
Pandas migrate long distances to switch between the shoots and leaves of two different bamboo varieties, according to the research led by academics at the Chinese Academy of Sciences.
The four distinctive diets provide different levels of key nutrients, with shifts between the diets enabling the pandas to balance their calcium, phosphorus and nitrogen needs to successfully reproduce, researchers said.
"We were surprised to discover that pandas arrange their migratory and reproductive habits around the nutritional qualities of two specific bamboo varieties, arrow bamboo and wood bamboo," said Professor David Raubenheimer from the University of Sydney's Charles Perkins Centre, Faculty of Veterinary Science and School of Biological Sciences, and co-author of the research.
The findings have profound implications for the conservation of China's iconic species, particularly given the accelerating environmental changes that threaten to transform the prevalence and location of the two bamboo species, researchers said.
"Pandas in the Qinling Mountains of China move from valleys up mountains in spring, and then move back again in autumn," said Raubenheimer.
"The summer forage contains high levels of protein, needed for muscle growth, but is very low in calcium, which is required for milk production and bone growth. By contrast, the winter forage has high levels of calcium but is low in protein.
"It is only by migrating seasonally, therefore, that pandas can obtain enough of both essential nutrients to breed," Raubenheimer said.
The researchers tracked six pandas in China's Foping Reserve with GPS collars over a period of six years, also conducting behavioural analyses and studying food and dung samples during the four foraging cycles.
The nutritional balancing observed in the pandas is a key factor in the survival of the endangered species. Despite being exclusively herbivorous, the giant panda retains the simple stomach and short gastrointestinal tract of its carnivorous bear cousins.
As a result, the preservation of its highly specialised diet is crucial to the continued existence of the species, researchers said.
The research is published in the journal Functional Ecology.