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panda cubs

447

Panda Cub: Rolling and Tumbling

The little cutie seems to imitate his father's relaxed eating style.

The little cutie seems to imitate his father’s relaxed eating style.

As the San Diego Zoo’s panda cub, Xiao Liwu, gets more and more confident in his enclosure, we are beginning to see some fun new behaviors from him and his mother, Bai Yun. So far, at least once a day the cub is coming down out of the tree to get some exercise with his mom and possibly nurse. The time frame and duration of his stay out of the tree has varied from day to day. Xiao Liwu enjoys coming down and jumping on his mom’s back and wrestling with her, and Bai Yun has been super patient and puts up with quite a bit of biting from her little one.

Bai Yun has been extremely relaxed these days and is maintaining a stable weight of 230 pounds (104 kilograms). She is not too rough with her cub and is showing off those mommy moves that we all love so much. As Xiao Liwu is teething and trying out the bamboo, Bai Yun has been surprisingly calm about him getting into her food and trying new pieces. When he initiates a wrestling match, she has been very obliging.

Two days ago, the cub gave our guests a heart-stopping moment—he fell out of the tree from about 20 feet (6 meters). As keeper Jen and I were talking, the cub was in the tree playing on a new branch and trying out some new moves. We looked up for a second, and Xiao Liwu rolled out of the tree! Wu never made a sound—just got right back up and continued playing. He’s moving just fine, and Bai Yun was not alarmed at all by the little oops he made from the tree.

Now I know some of you will be wondering if we need to check him or why we didn’t grab him, and the answer is simple: he’s tough! We did not see any limping or stress behavior from either Mom or cub. Panda cubs are designed to make those climbing mistakes at this young, bouncy age. That layer of baby fat helps, too!

So keep on watching and come see us soon. Just a word to the wise: there is NO schedule for when the cub comes down to play, so please remember to give him some time.

Anastasia Horning is a panda narrator at the San Diego Zoo.

UPDATE: The main panda viewing area is currently closed as we make modifications to it. Bai Yun and Xiao Liwu have been moved back to the north exhibit, where they can be viewed by guests. Pandas Gao Gao and Yun Zi are off exhibit during this time.

408

Panda Cub: The Den

A boy and his moat!

A boy and his moat!

As of January 17, Bai Yun showed us keepers that she is done using her den. How? By leaving a fecal sample in there. When this happens, we clean the den (remove the bedding and disinfect the floor) and close the den door for good. Xiao Liwu is now old enough where he will be spending most of his time high in the trees with Mom.

Some of our panda fans have been curious to know about our panda cub’s nursing activity. Xiao Liwu and Bai Yun both decide with he nurses these days. He seems to nurse early mornings and early evenings. I am sure he nurses throughout the day, as we are not always watching, but it’s not on a regular schedule, since he nurses when he wants to!

We do weigh him regularly and have the nutritionist look at him to body score him. The body score is a great tool to measure body fat and hydration levels. At his exam on January 15, Xiao Liwu weighed 17 pounds (7.8 kilograms) and measured 33 inches (85 centimeters) long.

Click to enlarge chart

Click to enlarge chart

One of our readers asked if baby pandas shed their coats, like human babies get new hair later on? When panda cubs start getting fur, it has a slightly pink tinge to it. We call it “baby fur.” As they reach around 5 to 6 months, the pink fur does grow out and shed. Have any of you noticed this with Xiao Liwu?

Jennifer Becerra is a senior keeper at the San Diego Zoo. Read her previous post, Happy 10th Anniversary, Gao Gao.

15

Black and White on Horizon

Our newborn cub is kept safe in Bai Yun’s protective arms.

Giant pandas are renowned for their distinctive black-and-white pelage; for many, it’s hard to relate the squirmy, pink giant panda neonate to the iconic fluffy black-and-white of older panda cubs. However, this long-tailed pink phase doesn’t last long, and by two weeks of age, the black-and-white markings on the panda cub’s skin are typically fairly distinct and herald the onset of a whole suite of developmental changes.

Of course, in the days soon after birth, the most important developmental changes we look for are simply continued growth and signs of vigor. We assess these characteristics by looking for a full belly (see Panda Cub: Big Belly) and loud squawking vocalizations. Both of these traits are most evident when Bai Yun leaves the den.

But the change in skin color, presaging the development of true fur, is another exciting and important milestone to watch for. Beyond the inherent cuteness of panda cubs at this stage, it also serves as an announcement, to all of us, that the most fragile period in the cub’s life has passed. So keep your eyes peeled, and look for the subtle color changes in about a week. When I see that change, I will start to sleep a little easier!

Right now, Bai Yun has her little cub tucked neatly under her chin, and they are both resting calmly. It is a beautiful sight to see and makes it hard to believe how quickly things will change for both Mom and cub.

Megan Owen is a conservation program manager for the San Diego Zoo Institute for Conservation Research. Read her previous post, Panda Den Cam.

122

A Bit about Breeding

Yun Zi, a happy result of natural breeding.

Recently, the Zoo Atlanta female panda experienced estrus, and some of you asked questions about the merits of artificial insemination versus natural mating. I thought I would take the opportunity to answer some of your questions here.

Bai Yun did not experience an estrus this year because she is still caring for Yun Zi, now 10 months old. The typical inter-birth interval for wild pandas is known to be two to three years. In the time between birth, a female is lactating to support the growth of her cub, and lactation suppresses estrus. This makes good sense, in that it would not serve a cub that cannot yet survive exclusively on bamboo if its mother were to become pregnant again and go through the denning-up process before a birth. This would leave a vulnerable, dependent cub out in the cold and reduce its chances of survival. Thus, in pandas as in many mammals, lactation by the mother precludes an estrus for a time.

Once estrus occurs, bears in captive breeding centers have two potential options for inducing pregnancy: natural mating or artificial insemination (AI). Natural mating is the preferred method, because it is more reliable in producing pregnancy. The males seem to know best when to time their copulations with the females, and perhaps fresh sperm from a male in these circumstances is more likely to get the job done. AI, which has produced Hua Mei and three cubs between National Zoo and Zoo Atlanta, obviously does work. However, despite these successes, there are more stories of failure of AI to result in pregnancy. For example, the procedure was done on Bai Yun in 1998, 2001, and 2002, to no avail.

In China, they often naturally mate a female with a male and then also perform AI with the sperm of a different male. When researchers did paternity tests on bears born before 2002, they found that in nearly every case, a cub’s father was determined to be the male that had naturally mated. Thus, despite the prevalence of AI as a technique in captive propagation of rare species, for some animals there is just no substitute for good ol’ fashioned male-female canoodling!

An interesting aside: bears that have more than one cub in their litter might just have more than one father for the litter. It is well known that female pandas, as with other bears, can mate multiple times during an estrus. Further, a female might find herself surrounded by many males at the peak of her estrus. This gives her the opportunity to mate with more than one male during her period of receptivity. Although I know of no case in pandas where multiple paternity has been confirmed for a particular litter, it has been confirmed in American black bears.

Zoo Atlanta has had great success with their AI process in recent years, and we are hoping their trend holds in 2010 as well. It would great to add another U.S.-born panda to the population!

Suzanne Hall is a senior research technician for the San Diego Zoo’s Institute for Conservation Research.

107

Panda Attraction

Yun Zi

Neoteny: reaching sexual maturity while retaining juvenile characteristics.

Pandas are so cute. What draws us to them? Why does the panda appeal to so many people? The answer might be neoteny—keeping a juvenile appearance into adulthood. Babies are cute. Our own young have characteristics that we humans respond to such as a big, round head, large eyes, a high forehead, and a roly-poly body. We are programmed to respond to these babyish looks. Babies just make us like them and want to care for them. It is part of our human makeup.

Human babies aren’t the only young that attract us. Puppies appeal to us. They have the short snout, big eyes, high forehead, and clumsy way of moving. The attraction we have for our own babies also endears us the young of many mammals.

But then these cute babies grow up and take on adult characteristics, like the brown bear, for example. Its cubs are adorable, with all the baby looks—short snout, big eyes, and high forehead, all cute and cuddly. But they grow up, the body changes and they have a long snout, smaller appearing eyes, low forehead, muscular body, hump on the shoulders, and a business-like gait. The brown bear is a very different animal as an adult, and our reaction to it changes. We are wary and fearful of the adult bears.

Now take the panda. The cubs have all the juvenile features—big head, eyes that appear to be big, high forehead, short snout, roundish, large head, roly-poly body, and wobbly gait. Except for being larger, the adult panda isn’t much different from the cub. The snout is short, as it doesn’t need a long jaw to eat bamboo. The eyes appear large, the forehead is high, the face is broad, and adults keep the roundish, roly-poly shape. So many of us continue to respond to adult pandas as if they are still cubs; even though they are fully mature, they look like babies. This is neoteny.

Chris Tratnyek is a panda narrator at the San Diego Zoo.