panda cubs


Panda Cubs: Interesting Individuals


At almost three years old, Xiao Liwu is a bundle of adorable energy!


In my previous blog, Meanwhile, in Panda Canyon, I mentioned that Xiao Liwu is “so different from his siblings…” Many of you have asked me to share more about the ways Mr. Wu is different, so here we go. To give you a good idea of what I mean, let’s take a “refresher course” in all the cubs born at the San Diego Zoo.

In August of 1999, Bai Yun, gave birth to her first cub Hua Mei as a result of artificial insemination from Shi Shi, the first male in our breeding program. As the very first giant panda cub to survive in the US, Hua Mei was a new adventure for our care staff and veterinarian team. Our nursery staff was on standby, but day after day, Bai Yun amazed us with her attentiveness to and care of her cub. Hua Mei was a typical, curious cub that became playful with her mother as she grew. The world watched her grow and fell in love with her—and her mom—via Panda Cam.

Gao Gao, our current breeding male, came to San Diego in 2003. He had never bred before and was a bit smaller than we anticipated, but Gao Gao rose to the challenge, and we had our first successful mating followed by another successful live birth on August 3, 2003. Named Mei Sheng, the first male cub for Bai Yun kept up with Hua Mei in weight in the beginning, even though he was a little smaller measurement-wise—different paternal genes can make a difference in size of an animal. Personality-wise, Mei Sheng was a little more clingy to his mom than Hua Mei, but he also had a goofy side. I remember when I first started working in Panda Canyon, he would sometimes hang upside down from tree limbs and swing. He was great fun to watch and was always putting on a great show for guests.

Our next panda cub, Su Lin, was born in 2005. She was one of our smaller kiddos, and I would definitely call her an “old soul.” She was pretty mellow, and sometimes seemed more sensitive to environmental change. Su Lin was the first cub trained to be part of the giant panda hearing study. Su Lin ended up staying at the Zoo until she was five years old, and during that time she went through her first estrus. Watching her scent mark her enclosure and even investigate her bedroom for possible denning was always interesting for guests and staff.

The birth of Zhen Zhen in 2007 brought a whole new experience for keepers! Physically, she kept up with Mei Sheng’s weight patterns as she grew, but Zhen Zhen had a little more of a feisty attitude. She had a lot of energy and used it to give Bai Yun a “hard time.” Keepers had to start training to go into her bedroom with mom sooner rather than later because with all of that energy, she would often attempt to roughhouse with keepers when they tried to gather her up to bring her in. As she got older, she still maintained a high-energy personality and was notorious for breaking tree branches from trees while bouncing on them.

An interesting side note: when Su Lin and Zhen Zhen went to China in 2010, we got reports from keepers there that their personalities had switched a bit. Zhen Zhen had mellowed out, while Su Lin now much more sure of herself, was putting on quite high-energy act for staff in China!

In 2009 Yun Zi was born. Nicknamed “Monster” as a little cub, he was ALL boy. He had a “I’m a big, tough bear” attitude even as a young cub. At the time, I was on loan as a panda keeper and was working with him five days a week. In the mornings when we would attempt to get Yun Zi “out of bed”, we would use all the amazing enrichment items that our donors had provided, but nothing seemed to work. In the end, dried leaves were the thing that got him up and moving—he liked chasing them down the tunnel that leads into the exhibit. We had another challenge at the end of each day, when we needed to get him back into the bedroom with mom. On more than one occasion, Yun Zi would be sleeping in the corner of the exhibit and we would have to carry him off exhibit. But as soon as you put him down in the bedroom, he “magically” woke up and began running around! Yun Zi was the biggest cub we have had born here at the Zoo. On more than one occasion, he was more than 2 pounds bigger than his siblings at the same age. Today, living in China, he is over 235 pounds.

And that brings us to the afternoon of July 29, 2012 when a little bear named Xiao Liwu was born. After five kids, Bai Yun was well seasoned for this cub and often when we would watch her you could tell that she was all about letting this kid figure things out for himself. “Wu Bear” has been very independent and what he may have lacked in size he has more than made up for in focus. He has always been a mellow cub, and as keepers have said many times, “They broke the mold after Wu Bear!” When we began training him to cooperate with having his blood pressure taken, he was calm, confident, and extremely relaxed. Not much fazes him, and for the most part—from a keeper’s point of view—he has been the easiest cub to work with.

Xiao Liwu will be turning three years old soon, and with that age comes a whole new set of behaviors and energy bursts. Just the other day, I was watching him put on quite a show for guests, running around and breaking off branches from the bushes in the enclosure. He will continue to be fun to observe and has a very bright future ahead of him—just like his older siblings.

2012 PandaCubGrowth

This chart shows Xiao Liwu’s early develoment compared to his siblings. (Click on the image to enlarge.)

Anastasia Jonilionis is a panda narrator and keeper at the San Diego Zoo. Read her previous post, Meanwhile, In Panda Canyon.

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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.


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.


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.


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.


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.