Panda-monium

Do I get a grade for recess?

“Yes, but I excel at recess.”

In their hilarious book The Animal Review: the Genius, Mediocrity, and Breathtaking Stupidity that is Nature, authors Jacob Lentz and Steve Nash assign grades to selected members of the animal kingdom. Great white sharks (“Nature’s perfect killing machines”) get an A+, even though they make “terrible pets.” Owls earn a sold B+ for being “a clairvoyant to the devil.” The giant panda, however, earns a solid failing grade. From its slovenly ways to its slow reproductive cycle, Lentz and Nash playfully assert that the giant panda is so inept that it is simply ill-suited for this world, and doesn’t even appear willing to raise a paw to save itself. With less than 1,600 giant pandas left in the wild, they ponder, “Maybe Nature is trying to give them the hint that they need to go the way of the dodo, and maybe we should spend our time on a species that at least wants to survive.” Though tongue-in-cheek, their message strikes a chord. As a species, the giant panda is in trouble. Shrinking habitat, encroachment by meddlesome humans, dwindling numbers, the ever-present need for vast amounts of food, and a rather slow and ham-fisted approach to reproduction all conspire to make maintaining the giant panda’s population, diversity, and natural lifestyle quite the challenge. The giant panda is not alone in this unique collision of dire circumstances. The almost certainly-doomed polar bear faces a rapidly warming Arctic Ocean, shrinking sea ice, and near starvation, thanks largely to human-induced global climate change. Yet it is the giant panda that zoos across the globe claw to obtain from the Chinese government, spending millions for a breeding pair on loan for ten years. Why does the panda get so much of our attention? And why does it appear that the giant panda is so difficult to save? There are no easy answers to these questions. But to begin to understand the multitude of issues surrounding this reclusive species, we must first delve into the giant panda itself, its home, its history, and its complex relationship with those pesky humans.

Humankind has had a mysterious, and sometimes contradictory, relationship with the giant panda. Though generally viewed with reverence in ancient China, this admiration did not generate deference for the giant panda’s reclusive ways. By some quirk of human nature, we tend to pursue, poke, prod, and parade what we admire, and in this the giant panda was no exception. The ancient Chinese captured giant pandas, doling them (or their pelts) out as rewards or gifts. They also gave captured specimens to a foreign government or dignitary on behalf of the Chinese government.

"I say, did they give you a green card too?"Ling Ling and Hsing Hsing at the National Zoo in 1985.

“I say, did they give you a green card too?”
Ling Ling and Hsing Hsing at the National Zoo in 1985.
(Image credit: Smithsonian Institution.)

Arguably the most famous participants of this “panda diplomacy” policy were Ling Ling and Hsing Hsing. In April 1972 the young pair arrived in their new home at the National Zoo in Washington, D.C. as a gift from the Chinese government, barely two months after President Richard Nixon’s historic visit to China. But panda diplomacy is centuries old, commencing at the latest with Tang Dynasty Empress Wu Zetian’s gift of a pair of giant pandas to the Japanese emperor. Despite veneration for these quiet woodland creatures (or perhaps because of it), giant pandas were also used in ritual sacrifices and funerary customs. At least one recently excavated 4,000-year-old tomb contained a giant panda skeleton, and Empress Dowager Bo was buried with a giant panda skull in 155BCE. As for medicinal uses for the giant panda, in the Qin Dynasty their pelts were thought to control menstruation; and in 2008 when the mainland Chinese government gave the people of Taiwan two giant pandas, the pair were transported to Taipei labeled as “Chinese medicinal products.” There is no report on how this alleged medicinal use affected their diplomatic potential.

It's medicinal.Tuan Tuan and Yuan Yuan in Taipei.

It’s medicinal.
Tuan Tuan and Yuan Yuan.

The giant panda’s mystery also extends to the creature’s common name, for even the origins of the word “panda” are shrouded in obscurity. The name doesn’t resemble any of the dozens of words in Chinese languages that have been used over the past 3,000 years for the giant panda. Some claim the name “panda” comes from the mauling of the Nepalese word for the creature’s unique wristbone (its sixth finger, which we’ll talk about later). Others say well-meaning biologists, attempting to trace the giant panda’s evolutionary origins, gave it the name “giant panda” under the mistaken assumption that it was closely related to a small, arboreal, rust-colored mammal called the red panda.

"Oh, brave new world!"Ruth Harkness and Su-Lin.

You’ve come a long way, baby.
Ruth Harkness and Su-Lin.

Speaking of those well-meaning biologists, the giant panda is especially a puzzle to the scientists who study them. Huge, slow, and shy, this single species doesn’t have a very large home. Giant pandas occupy only a few narrow isolated mountain ranges that ripple precariously along the eastern fringes of the Tibetan plateau. Its unique black-and-white coat combined with an immense size will always ensure that the panda versions of Where’s Waldo? will be a breeze for anyone over the age of 2. Yet, despite its obvious coloration, there wasn’t much Western scientists could conclude about the giant panda early on since they were so tough to locate, observe, and study. French missionary and naturalist Armand David became the first Westerner to observe evidence of the giant panda’s existence when he was shown several panda skins and pelts in 1869. It would be another 47 years before Hugo Weigold, a German zoologist, would see a live one. Accounts of the giant panda continued to trickle out of China for the first half of the 20th century. Theodore Roosevelt and his son Kermit allegedly shot one during the roaring ‘20s. In the next decade, socialite Ruth Harkness fulfilled her late husband’s quest of capturing a live giant panda and bringing it across the Pacific. In fact, she literally carried giant panda cub Su-Lin in her arms when she arrived in the United States.

Early attempts by scientists to understand this reclusive and contradictory creature centered on answering this basic question: what exactly is the giant panda related to? This question is far from trivial. To begin to understand a new creature – a new form of life – biologists often begin by asking where it sits in the tree of life. They want to know what organisms it is closely related to, and which ones it isn’t closely related to. This information about the giant panda would help scientists begin to understand how it evolved, what sorts of ecological roles it may play in its environment, and how it might (or might not) adapt to human interference. So from the moment Armand David first saw those panda hides in the latter half of the 19th century, the question became, “What exactly is the giant panda?”

It’s a question that might seem a bit absurd to 21st century eyes. After all, the giant panda looks like a bear, albeit with some deviations. For one thing, the giant panda’s head is more large and round (relative to its body size) compared to other bear species. It also sports its infamous and rather unorthodox black and white variegated coat, while most other bear species are nearly uniform in their chosen coat colors. Then there’s the matter of the panda’s diet. All bears are, to various extents, omnivorous: their diets consist of a mixture of plants and meat. The amount of plant vs. animal matter a bear consumes varies by species. The polar bear diet consists almost exclusively of meat, while the spectacled bear of South America eats very little meat. The giant panda, however, is nearly an herbivore. Over 90% of the giant panda diet consists of bamboo, a plant no other bear eats.

The giant panda’s overreliance on this woody grass for food may explain several other unique, un-bearlike characteristics of this creature. The giant panda’s aforementioned large, round head sports a powerful set of jaw muscles and large, durable molars, both of which may be adaptations for chewing this tough food. These are features that the panda’s long-extinct ancestor adopted some 3 million years ago, when it switched from a more omnivorous diet to the untapped bounty of the bamboo in its warm arboreal habitats. Some speculate that the giant panda’s trademark coat color may also be a bamboo adaptation, to keep the reclusive creature from standing out in its forest home. Bamboo may also be responsible for the giant panda’s most infamous characteristic: the sixth “finger” it sports on each of its forepaws. This sixth finger isn’t really a finger at all. It’s actually a wristbone (the radial sesmoid bone, if you’re really curious), radically modified to act as an opposable thumb. The giant panda uses this thumb, in conjunction with its traditional five digits, to grasp bamboo stalks for its lengthy meals.

Chew with your mouth closed. "Thumb" (radial sesamoid bone) clearly visible at left.

Chew with your mouth closed.
“Thumb” (radial sesamoid bone) clearly visible at left.

This wristbone/thumb partially explains some of the initial confusion over the giant panda’s position in the tree of life. The aforementioned red panda (a possible source of the giant panda’s name) also loves bamboo and has a similar sesamoid-modified “thumb,” but the similarities between these two creatures pretty much end there. With its slender small body (about 2 feet long, not counting a bushy striped tail) and ochre-to-brown coat, the 2 foot long red panda resembles a cross between a cat and a raccoon. More arboreal than the giant panda, the red panda also roams the dwindling forests of southwestern China. The Western world first learned about the existence of the red panda in the early 19th century, roughly 50 years before Armand David saw his first giant panda pelt, and biologists immediately tried to determine what this mysterious creature was. Many initially thought it was some sort of raccoon, though others couldn’t help but notice some bear-like or feline qualities. In a nod to the latter qualities, biologist Frédéric Cuvier gave the red panda the scientific name Ailurus fulgens (“shining cat”). When the giant panda came along, its similar bamboo diet and mysterious “thumb” ensured that it was swept up in the red panda’s identity crisis. Were they both raccoons? Were they both bears?

Identity crisis. Red panda: animal, vegetable, or mineral? (Image credit: Knoxville Zoo)

Identity crisis.
Red panda: animal, vegetable, or mineral?
(Image credit: Knoxville Zoo)

The debates shifted back and forth as new anatomical, ecological, and fossil data on these creatures poured in over the next century. The debate persisted well into the 20th century, when biologists could finally collect genetic data from these creatures. The results were striking, though in retrospect hardly surprising. The red panda and giant panda are not close relatives. Their “thumbs” are most likely a case of convergent evolution: an adaptation to eating large amounts of bamboo that both creatures independently acquired as their respective ancestors adopted a more bamboo-heavy diet. The red panda is not a bear, and is at best a very distant relative to raccoons and weasels; it occupies its own barren branch of the mammalian family tree. The giant panda, on the other hand, is definitely a bear. Geneticists believe it is a “basal” bear species, meaning the giant panda ancestor diverged from the bear family tree much earlier than most other living bear species. With the mystery of its evolutionary origins resolved, the only souvenirs the giant panda from this long debate are its scientific name, Ailuropoda melanoleuca (“black-and-white cat foot”), and its many common names in Chinese languages (most of which translate roughly to “bear cat”). So, with thumb and strong jaw fully engaged, this most unusual of bears can chew and chew, content that humans have addressed at least one piece of the panda puzzle.

And boy does it chew. Giant panda meals are so lengthy that it might be more productive to account for the time this creature doesn’t spend eating. Its gastrointestinal tract is still constructed along the lines of a bear’s (another line of evidence of its bear ancestry). Thus, the gut must work hard to break down, process, digest, and extract nutrients from the woody stalks and bitter leaves. Occasionally, pandas may supplement their diet with meat, eggs, or fish, but this is such a rare instance that the panda has even lost some of the genes it would need to taste meat properly. Bamboo appears to be what they want first and foremost. Unfortunately, bamboo is a very nutrient-poor food. To make up for bamboo’s low nutrient and protein content, adult pandas must eat between 20 and 40 pounds of bamboo daily, a monumental task that takes 10 to 16 hours per day. Even when the giant panda gets enough to eat, scientists theorize that this nutrient-poor food source may explain the creature’s relatively low metabolic rate. In addition, the giant panda’s slow, meandering lifestyle may be a mechanism to conserve energy, though they can sprint away or climb trees in a jiffy if needed.

In the wild, giant pandas are solitary, finding one another only for the 2-4 days each year when a female is in heat. For the other 361 days a year, they roam forests eating bamboo. They show a preference for the tender bamboo sprouts over woody stems, presumably since the former contain less tough fibrous material. Some panda populations also consume bitter bamboo leaves when available rather than stems, leading scientists to theorize that giant panda populations more genetically diverse than once thought. With giant pandas in the wild numbering at around 1,600 individuals, that’s quite a claim. However, a team of scientists from China recently confirmed that giant pandas, while few in number, show a high degree of genetic diversity. They are not the dwindling, inbred “evolutionary dead-ends” that some imagined, including the authors of The Animal Review. Genetic data indicate that over the past 300,000 years, the giant panda has diverged into at least three distinct populations. All of them are clustered along mountain ranges and valleys east of the Tibetan Plateau. But, fossil evidence shows that their past range was much larger, and that their fortunes waxed and waned as their beloved bamboo forests grew and shrank in response to successive ice ages. During one time of plenty, with their forest habitats covering much of east Asia, giant pandas roamed large swathes of eastern and southern China, as well as northern parts of Burma and Indochina. For their current restricted habitat, giant pandas can thank two forces of nature: the last period of glaciation and the arrival of humans. The former penned them into the mountains east of Tibet, while the latter further eroded their territory with massive deforestation. As ancient agricultural settlements grew into towns, towns into cities, and cities into kingdoms, road construction and trade routes also made it difficult for giant pandas from different populations to intermingle. Thus, it appears that the decline in giant panda numbers since the last period of glaciation is due almost exclusively to human activity.

Up in the air. What does the future hold?

Up in the air.
What does the future hold?

So, what’s next for the panda? This most unusual of bear species has survived and thrived for millennia, with its fortunes tied intimately to the temperate forests housing its precious bamboo. But like countless other creatures great and small, it hasn’t adjusted well to human intrusions, though today we appear to be the giant panda’s best chance at survival. China now has nearly 50 giant panda sanctuaries and preserves for rearing young pandas. Scientists are gathering new data on panda population structure and diversity at a furious pace to better understand which populations are most at risk by human intrusion and habitat destruction. Decades of breeding programs in sanctuaries and zoos worldwide have provided a wealth of data on panda reproduction, physiology, and nutritional needs. While this wealth of scientific data is necessary, the panda’s ultimate fate will be decided in its forests. Government and environmental organizations must take concrete steps to save the giant panda in its natural home to keep this creature from going the way of the dodo. The to-do list is massive: curb deforestation, preserve existing habitats, connect isolated populations to maintain genetic diversity, clean up pollution sites, curb illegal poaching and the exotic pet trade, and educate local communities on the importance of panda preservation. These are drastic steps, but there are only 1,600 giant pandas left in the wild. They can wait for us to step up, but not for long.

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About James Urton

I went to school to become a molecular biologist.  At some point in this long education, I discovered that I love communicating science to the general public: talks, writing, at a pub, on the street corner...  Whatever venue will let me hold your attention for a few moments.  Unfortunately, I can't do this for a living, since no one will pay me.  So, I have a job as a molecular biologist at the University of Washington, where I get to work with great scientists on some really awesome projects, and I'll blog about science here at Muller's Ratchet in my spare time. Why should the general public want to know anything about science? Here's my explanation (which also explains why I chose the name Muller's Ratchet for this site). Briefly as a graduate student (before I had to devote all of my time to graduating), I blogged at Adaptive Radiation.
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