Giant Pandas: Bamboo Bears
by Devra G. Kleiman
and Hsing-Hsing’s arrival in Washington in 1972 marked
the official beginning of my long years of studying giant
pandas at the National Zoo. (I have to admit to informal and
somewhat surreptitious observations of London’s Chi-Chi
and Moscow’s An-An during their ill-fated breeding encounters
in London in 1968.) Since 1978, I have also visited China
several times. But I have always watched giant pandas in zoos
or breeding centers, even though one breeding center is actually
within the Wolong Natural Reserve - site of one of the longest
ongoing studies of giant pandas in the wild.
of these years, however, I’ve had another vision. I dream
that someday I will be able to study giant pandas in the wild.
I imagine following a female giant panda to her maternity
den and, over a series of months, watching her raise twin
young to maturity. Then I imagine returning years later to
find her now-mature offspring successfully breeding, and I
stay to watch their progress. The dream unfolds in a belt
of temperate conifer forest with an understory of never-ending
bamboo along the slopes of the Min Mountains in Sichuan—a giant panda Garden of Eden.
dream be realized? It’s hard to say. Adequate habitat
for this species is becoming rarer and rarer in China. Giant
pandas are starving, not only for bamboo—their staple food—but also for enough land for long term survival.
to a few mountain ranges in western Sichuan, giant pandas
once ranged widely throughout China. Fossils have been found
almost as far north as Beijing, within several hundred miles
of China’s east coast, and as far south as Guangzhou,
as well as in Burma and Vietnam.
shrinking of the giant panda’s distribution is a result
of both natural and human-induced changes in the Chinese landscape.
During the Pleistocene glaciations that began nearly a million
years ago, vast areas of China alternately warmed and cooled.
Giant panda habitat likely expanded and contracted with these
climatic changes. During the last warming period, perhaps
10,000 to 20,000 years ago giant pandas probably became restricted
to the mountain ranges bordering the Tibetan Plateau and a
few other high-altitude or cool habitats capable of supporting
the bamboo to which they are so superbly adapted. Many of
the sites they once occupied are now subtropical in climate
and could not possibly sustain giant pandas.
but ultimately more serious change, was the vast increase
in human activity that began even in ancient China. An expanding
Chinese population decimated low-lying bamboo forests for
agricultural purposes, pushing the giant panda up into higher
and higher altitudes. Historical records show that the giant
panda’s range is now less than 10 percent of what it
was 2,000 years ago, and it continues relentlessly to get
smaller still. With ever-increasing pressure from the one
billion inhabitants of China the likelihood that giant pandas
will survive the next 50 years remains iffy at best.
pandas are only the most dramatic-looking of a unique fauna
and flora that survive precariously along the edge of the
Tibetan Plateau. (See China's
Wildlife Wonders) Golden monkeys, takin, red pandas, and
an array of colorful pheasants live in the same mountains
as the giant pandas. All are now vulnerable to extinction
as people continue to destroy the ecological integrity of
the Min, Qinling, Liang, and Qionglai Mountains.
slopes are also home to an amazing radiation of bamboo species,
upon which giant pandas depend for 99 percent of their diet.
At least two species of bamboos usually grow within good giant
panda habitat. The life history of bamboos can dramatically
affect giant pandas. These particular bamboos tend to flower,
set seed, and die at species-specific intervals of 30 to 80
years. Plants of any particular species do this in synchrony,
leading to a massive die-off of that species throughout its
range, followed by slow regeneration. (See Bamboo)
the aftermath of recent bamboo flowerings in giant panda habitats,
Alan Taylor of Pennsylvania State University learned that
bamboo regenerates more rapidly if it receives some cover
from the forest canopy. Where the forest has been clear-cut,
as it has in much of the giant panda’s potential habitat,
bamboos regenerate very slowly. Thus, bamboo regrowth - and
in the best of situations it takes 15 to 20 years for bamboos
to regain their full height - depends on forest integrity.
the long regeneration period, giant pandas have traditionally
had two options. They could switch to eating a second, less
preferred bamboo species, or they could move, usually to an
area where the local bamboo had not flowered and died. But
now, because their habitat is so fragmented, the migration
option is becoming less and less viable for giant pandas faced
with severe food shortages. With the lower mountain slopes
being used for agriculture, the distances between habitable
areas have become too great for giant pandas to traverse.
Only secure "corridors" of natural habitat linking
larger areas of panda habitat will alleviate this problem.
pandas are a study in the evolutionary process. Their most
recent ancestor was a bearlike creature. Like other bears,
giant pandas are technically carnivores—members of the order
Carnivora. But, in fact, most bears are omnivores - they will
eat almost anything, including meat, fruit, seeds and insects.
But at one stage in their evolutionary history, giant pandas
abandoned omnivory in favor of strict herbivory—eating green
vegetation. Indeed, going a step farther than most herbivores,
giant pandas even limited themselves to a single sort of grass—bamboo.
adaptations for feeding on bamboo make them morphologically
unique. Giant pandas possess huge molar teeth and powerful
masticatory muscles for breaking the woody portion of bamboo
and chewing the stem, culms, and leaves. In addition, their
forepaws are equipped with a sixth "digit" that
acts as a thumb for holding bamboo. This "thumb"
is derived from the radial sesamoid bone of the wrist.
as it may seem to observers of giant pandas in the Zoo, black-and-white
coloring probably acts as camouflage in the wild. In patches
of dense bamboo, an immobile giant panda is nearly invisible,
and virtually disappears among snow covered rocky outcrops
on a mountain slope. The combined effect of foreshortened
snout, round face, black eye rings, small rounded black ears,
short squat tail, and distinctive body shape and markings
gives the giant panda its characteristic infantile appearance,
which is further enhanced by its habit of sitting upright,
holding objects in its flexible forepaws, and walking pigeon-toed.
of the year, individual giant pandas use fairly small home
ranges: In good habitat they can find all the bamboo they
need without moving very far. Males and females roam over
areas varying in size from about one to 10 square miles, with
little difference between the sexes. Some females studied
by George Schaller in Wolong even occupied home ranges as
small as 75 to 100 acres—less than the size of the Zoo.
Seasonal as well as long-term changes in the availability
of preferred foods, and the location of potential mates, sometimes
results in pandas taking very long hikes outside of their
normal territory. But more often they migrate vertically,
up and down the mountainside, to find a preferred bamboo species
or preferred parts of bamboos. Giant pandas normally exist
at altitudes of 3,600 to 10,500 feet, depending upon prevailing
local conditions; for example, in Wolong Reserve, the giant
pandas occupy habitat from 7,550 to 10,500 feet, while in
Shaanxi’s Foping Nature Reserve, the giant pandas remain
at 3,600 to 9,500 feet.
by George Schaller, Hu Jinchu, and others suggested that the
giant panda is essentially solitary in nature. They found
that males and females rarely interact except during the breeding
season. At this time, males may also meet in the neighborhood
of a female in heat, when they show a dominance hierarchy.
based on a study of radio-collared giant pandas in the Qinling
Mountains, Pan Wenshi and Lu Zhi, of the Beijing University,
recently suggested a somewhat different picture of panda social
life. They found that seven to 15 individuals may form a social
community of pandas within the local population. These individuals
occupy a "group" territory, within which male home
ranges overlap almost completely while female home ranges
overlap far less. Members of different "groups"
generally avoid socializing with each other.
exciting new results suggest that giant pandas are far more
social than we previously believed, and also raises important
questions about whether mating occurs exclusively between
members of these small groups. If so, and if pandas in other
mountain ranges have similar social groups, we will need to
reevaluate our interpretation of the giant panda’s genetic
example, a mating system that is restricted to "group"
members would likely result in giant pandas being genetically
inbred in local populations. Yet, genetic analysis of blood
from a small number of giant pandas, performed by Steven O’Brien
of the National Cancer Institute, showed that the species
retains considerable genetic diversity. Clearly, this is a
question that requires further study, because the answers
could have a significant impact on conservation strategies.
and Lu findings are similar to some behavioral observations
made on giant pandas in zoos and reserves. First, males can
be maintained in small groups without aggression if the males
have been very carefully introduced to one another. Usually
the males develop a clear dominance hierarchy. Second, female
giant pandas seem to prefer mating with specific males, usually
males that they have known well for a long time. They seek
out the preferred male or males during estrus, using a series
of very elaborate vocalizations and behaviors that to a human
seem almost coy.
patterns that giant pandas use to communicate with each other
reflect the dense habitat in which interactions occur, and
the generally low level of sociality. Visual signals—body
language, facial expressions, ear and mouth movements—are
exceedingly rare because the dense bamboo understory restricts
vision and visibility. In addition, massive cheek teeth and
masseter muscles make subtle mouth, ear, and eye movements
giant pandas use vocalizations and sounds extensively in social
interactions. Indeed, the subtleties of expression that can
be seen in the faces of many primates can be heard in the
gradations of sounds and the combinations and recombinations
of vocalizations of giant pandas. Listening to the complexity
of communication between Ling-Ling and Hsing-Hsing during
social and sexual encounters always awes me. Giant pandas
also use scent to communicate. They rub the large gland that
covers their anogenital region on objects, often at the edge
of their territory, where a thick, waxy, strong-smelling deposit
soon builds up. Both males and females may also urinate at
marking sites, adding additional odor information.
marks are placed at nose level or higher. Giant pandas use
complex scent-marking postures to deposit urine and secretions
at different heights; they even perform hand stands to raise
their posteriors to make elevated scent marks.
based on odor alone, a giant panda can probably identify the
sex, age and individual identity of the scent marker, as well
as interpret the marker’s mood and reproductive status
at the time it left the scent mark. Because the scent is not
ephemeral, as sounds are, giant pandas may be able to tell
not only who has visited a particular site and how he or she
was feeling, but when the visit occurred! Thus, giant pandas
accomplish with scents and sounds what we accomplish with
visual and auditory signals.
panda reproduction is unique among mammals. Mating styles
vary considerably among different pairs. In some pairs, male
and females mate just once and the female becomes pregnant;
other pairs may copulate several times a day for two or three
days. Regardless of mating frequency, female giant pandas
conceive only during their two- to three-day estrous period,
which occurs just once a year in the spring, and they show
no interest in mating at any other time. Males are sexually
active for a longer period in the spring, allowing them to
attempt to inseminate more than one female.
pandas exhibit another peculiar evolutionary adaptation known
as delayed implantation. A fertilized giant panda egg does
not immediately implant on the mother’s uterine wall,
but instead "floats" around in her reproductive
tract for varying lengths of time. As a result, we do not
know precisely the length of the giant panda’s actual
gestation period. All we can say is that the time from mating
to birth ranges from 95 to 160 days.
implantation gives the giant panda more control over when
cubs are born because birth dates are not precisely fixed
by mating dates. Young may be born in the late summer or in
the fall. Overall, however, the general timing of giant panda
reproduction is determined by the importance of weaning cubs
in the spring, when the newest most protein-filled bamboo
shoots are available. This gives cubs the best possible start
in life on a diet that in the best of conditions is of poor
poor, low-energy bamboo diet prevents giant pandas from devoting
much energy to gestation or lactation. As a result, giant
pandas are the smallest newborn of any nonmarsupial mammal
and they grow very slowly. Giant panda infants weigh just
four to six ounces at birth and young are a year old before
they reach 75 pounds, which is about one-third of adult weight.
And this growth rate is based on giant pandas in zoos, where
mothers are fed rich diets, with fruits, vegetables, meat,
vitamins, and minerals supplementing their daily ration of
bamboo; growth of cubs in the wild is likely to be slower
giant pandas do not reach sexual maturity until they
to six years of age, but even young, inexperienced
demonstrate a strong maternal urge and know, without
how to care for their young. This is important
breeding season is "wasted" through clumsy
parenting—something a female panda cannot afford. Giant pandas start
to breed late, and then usually rear just one young
two years. Because a female is considered old, and
post-reproductive, by the age of 20 or 22, a female
at most, about seven young in her lifetime. The
low reproductive rate makes it very difficult for a
panda population to recover from a decline in
and 1991, two myths about giant panda reproduction were debunked.
More than half of all giant panda litters are twins, but it
was widely believed females could never raise both of them.
Then researcher at Wolong discovered a giant panda den with
twin infants, both of which looked fit and thriving. Almost
simultaneously, a giant panda female named Qing-Qing in the
Chengdu Zoo gave birth to twins, and, against all predictions,
reared them both, although with some human help.
the twins were about a month old, one was found to be gaining
less weight than its sib. So zoo staff began a routine of
each day removing one cub from Qing-Qing so it could be hand-fed
for 24 hours. Cubs were alternated so each received extra
nourishment every other day. Clearly, this procedure could
be used only with a very calm, nearly tame female, but it
was successful. By January 1991, when I had the pleasure of
seeing these twins, they were about five-and-one-half months
old, weighed 21 pounds each, and were still thriving.
myth was that a giant panda cub could not be human-reared
from birth. At the Heptaoping Breeding Center in Wolong, a
twin was human-reared, thanks to the combined efforts of staff
from Wolong, the Beijing Zoo, Chengdu Zoo, and Susan Mainka,
a veterinarian who recently left the Calgary Zoo to over-see
Wolong research programs.
the past two decades, giant panda conservation has received
considerable support from the international community. Nevertheless,
the wild giant panda population is steadily declining, and
recent successes with captive breeding have not made up for
the losses, either in the wild or in zoos. Giant pandas are
still being poached, timber is still being extracted from
the best habitats, and the local people are still degrading
what remains. A conservation action plan developed by the
World Wildlife Fund and the Chinese Ministry of Forestry was
completed in 1988 but has to be approved by the central government.
[Editor's Note: Since this article was first published in
1992, a version of this plan has been approved by the Chinese
not sure I’ll ever have the chance to follow a wild giant
panda female and her descendants in a pristine bamboo-covered
Garden of Eden, as in my dream. And I wonder whether our grandchildren
will ever see a giant panda at all.