A new study on the skulls of Red panda (Ailurus fulgens) and Giant panda (Ailuropoda melanoleuca), published in the journal Biology Letters, offers explanation as to why these two mammals are able to coexist.
Left: Red panda. Image credit: CC BY-SA 3.0 Right: Giant panda Bai Yun with a cub, Xiao Liwu, at the San Diego Zoo in December 2013. Image credit: San Diego Zoo.
“Scientists have been studying the differences between Red pandas and Giant pandas for a long time because there’s a basic principle in ecology that says if two species of an organism utilize the same resources, they cannot live in the same space. There’s too much competition,” explained study co-author Dr Z. Jack Tseng from the American Museum of Natural History.
This research contributes to the body of work showing how the pandas co-exist. We’ve found that fundamentally, based on the structure of their skulls, they cannot eat the same things.”
Using high-resolution imaging and biting simulations, Dr Tseng and his colleagues found that the skulls of the two panda species not only are distantly related but also have structural differences related to the way the animals chew.
These substantial differences reflect distinct bamboo feeding preferences, with Red pandas foraging on softer parts of the plant and Giant pandas seeking out the tougher stems.
The Red and Giant pandas are mammalian carnivores separated from each other by about 40 million years of evolution.
The Red panda is most closely related to animals like raccoons and weasels and weighs about 4.5 kg.
The Giant panda is a member of the bear family Ursidae, and it is much larger, weighing about 100 kg.
Their geographic ranges overlap in southern China, and both animals have independently adapted to a diet consisting mainly of the same bamboo species.
The skull of the Red panda is better at distributing mechanical stress during chewing than the skull of the giant panda.
But the Giant panda has a stronger skull that can withstand greater forces that are more concentrated and could be more damaging, even after accounting for the size differences between the two species.
“These differences tie into the way that the species actually process bamboo. The Giant panda is a less-refined eater: it does a lot of chomping and swallowing,” Dr Tseng said.
“Their skulls are stronger overall, so the peak biting stresses are lower, meaning that they can eat harder and larger pieces of bamboo.”
“The Red panda has a weaker skull but it’s better at distributing stresses, allowing it to chew longer and break down soft bamboo leaves more thoroughly before they swallow them.”
“These links between dietary preference and skull performance provide an engineering basis for explaining how the co-existence of the two panda species is possible.”
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Borja Figueirido et al. 2014. Three-dimensional computer simulations of feeding behaviour in red and giant pandas relate skull biomechanics with dietary niche partitioning. Biol. Lett., vol. 10, no. 4; doi: 10.1098/rsbl.2014.0196
