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The Zoo Journal

77

Let Her Eat Cake—Whenever!

Bai Yun gets all the toys and treats for herself!

Yesterday was Bai Yun’s 19th birthday, and she was presented with a cake befitting her age and station—not too big, not too flashy—early in the morning. She is, after all, no “spring chicken” but a female of mature station, so a modest cake to mark the day without a big fuss, just a gathering of a few close friends to help celebrate.

And so it was that morning, with a lovely little (by panda cake standards) cake, crowned with apple slices and bamboo and three juicy apple halves frozen inside. But this is Bai Yun, after all, she who will grab food out her cubs’ mouths, all-food-is-Bai-Yun’s-food Bai Yun, with years of experience now in the care and eating of birthday cakes, both hers and her cubs’. Did she rush with joy to devour it? Did she make a beeline to this wonderful offering? Of course…NOT! There were piles of biscuits and fruit to be scoured first, and the bamboo pile, now being shared increasingly with Yunni, to be perused, as the small group of visitors grew larger and larger. When she finally did approach this lovely treat, a nearby log captured her attention.

Could it be that she was teasing her adoring public? Who knows? But what is obvious is that when she finally turned her attention to the “cake,” it was with a practiced eye and paw, pulling out the carrots, gobbling off the apple, and a quick swipe to see what else she could pry loose. That’s all? No problem. Bai just rolled it to the front of the exhibit to thaw out! Experience has taught her that eventually, all the goodies will pour forth when the ice softens enough, so she simply keeps rechecking from time to time to see what’s been melted out.

What a bear! It’s no wonder that she’s so special to us all! Happy Birthday, Missy B! You are the world’s most perfect panda—just ask us!

Ellie Rosenbaum is a panda narrator at the San Diego Zoo. Read her previous post, Yun Zi and the Door.

168

Bai Yun through the Years

Happy 19th birthday, Bai Yun!

I remember that special day in the fall of 1996: the dream had finally happened, the San Diego Zoo had giant pandas! I had little sleep the night before our black-and-white celebrities arrived. I stayed late at the Zoo’s Giant Panda Research Station, disinfecting bedrooms and getting things ready for our new kids. Bai was the first panda I saw in the shipping crate when she and Shi Shi arrived. As the back door of the delivery truck opened, there she was, looking curiously at me. I was in awe!

Bai checks out her new home at the San Diego Zoo, October 11, 1996.

As the days rolled into months, Bai and I became fast friends. I would spend my lunch breaks with her:she would be in the off-exhibit backyards, and I would be on the outside of the separation fence. Bai was five years old at the time and very much the comical youngster. We would interact through the fence line, and it was funny, as it seemed she would imitate everything I did! If I ran along the fence line, she would run; if I did a somersault, or bounce on all fours, Bai was with me every step of the way. Thank goodness we were behind the scenes, as someone might think the keeper has lost her mind!

Bai knows how to play! April 1997.

Bai and I have shared many events together. I remember during the early years of breeding season, male Shi Shi repeatedly rejected Bai’s friendly advances. Our Panda Team decided to precede with our alternate plan, and Bai was artificially inseminated; this procedure eventually produced our first cub, Hua Mei.

I was there the day Bai gave birth to Hua Mei. At that time, some people were skeptical about whether Bai would make a good mother. I had no doubts, as I knew her that well; she would know what to do and care for her cub. Bai has now proven herself to be an excellent mother five times to date!

Who needs a hammock? September 2001

Another story that comes to mind is when our vet staff asked us if there was a possibility we could train Bai to do ultrasound procedures. In three days, Bai learned to lie down in a squeeze cage when asked, and within a few weeks we were obtaining ultrasound pictures! How did Bai learn this behavior? Well, she imitated me while she was sitting in the cage: I laid down next to the cage, and my silly girl thought this was a new game to play! I captured this behavior using a clicker and a food reward after she did the behavior. Bai never ceases to amaze me. Since the early years, our veterinarians have been able to document the development of a growing panda fetus up to the day before birth!

Bai checks out an interesting scent, June 2003.

As I look back on the early years to the present, I still am in awe over Bai Yun. She has taught us so much about giant panda biology. Through her, researchers have been able to utilize this knowledge in efforts to better understand giant pandas in the wild and how we can protect and preserve giant panda habitats in China. Our Bai is truly the matriarch of our conservation research program here at the San Diego Zoo’s Giant Panda Research Station.

Today, September 7, our grand lady is 19 years old. She is still just as beautiful as the day she arrived in 1996, a bright-eyed beauty who still captures the hearts of everyone who sees her at the Zoo and on our Panda Cam.

Happy Birthday, “Miss B”! Thank you for all you have done for us in the name of giant panda conservation, your five beautiful cubs, and for me personally. I am honored to be your keeper.

Kathy Hawk is a senior keeper at the San Diego Zoo. Read Kathy’s previous post, Panda 1st Grade.

121

Yun Zi and the Door

As he grows and develops, panda yearling Yun Zi is undergoing the same husbandry training regimen as his siblings have before him. Since these bears will live their lives in managed care, it’s important that they can transfer on and off exhibit at the San Diego Zoo Giant Panda Research Station easily and quickly, responding in a positive way to their keepers’ requests, and that the training starts early and slowly. Now around 55 pounds (25 kilograms), Yunni is quite the double handful, literally and figuratively. He’s a strong, healthy, and playful little panda and, as far as he’s concerned, whether it’s Mom or keeper, he’s up for panda play. His teeth and claws at the ready, he’ll grab and pounce—not a problem for his furry mother but not such a good idea for the keepers, so it’s necessary for him to be off exhibit, in the bedroom, when keepers are servicing the exhibit.

Now, Bai Yun knows the system: the green door opens and in she goes, to be rewarded with a treat for her cooperation. Sometimes she has to be called, sometimes the added incentive of a rattling treat bucket is necessary, but it’s usually a swift and smooth transfer. For Yun Zi, however, it’s another matter. Keepers are in and of themselves enrichment items—variable items in the pandas’ environment—and he loves to stay and play with them. But on the ground, he can injure the keepers without meaning to, so it’s better for all concerned that he leave the enclosure with his mother. But keepers are so much fun. But he’s so strong. Sigh.

Day by day, transfer by transfer, keepers are calling, cajoling, and encouraging him to follow Mom’s lead, with mixed results. If, despite their best efforts, Yunni stays put, it becomes the job of one of them to heft him up from behind (mind those claws, now) and carry him to the transfer tunnel. He’s placed in a section that’s separated from Bai Yun; the adjacent gate is then opened so that they are reunited in the bedroom. (Before you all melt with envy, think about this: 55 pounds of squirming, bear-smelling mischief. Okay, I know—it’s still pretty cool!) When the cleaning and feeding are done, the green door opens, and the pandas return to the exhibit…maybe.

For Bai Yun it’s the same routine, so out she comes, but a young, inquisitive cub like Yunni has to investigate his whole world (“Oh, look—a leaf!”) and is often easily distracted on his return to the exhibit. When this happens, the door remains open, and we all have to wait patiently for him to emerge.

Patience is the key with any training routine, and our keepers and behaviorists have it abundance; it’s a part of the job. Yun Zi is a smart little bear and has mastered other aspects of his husbandry routine with ease. We have no reason to believe that he won’t be a star pupil in this as well.

Ellie Rosenbaum is a panda narrator at the San Diego Zoo. Read her previous post, A Bittersweet Time.

Update: Thanks to all of our generous panda fans, our goal has been reached for the rental of a crane to place large climbing structures into the pandas’ exhibit!

173

One More Thing Before They Go

Su Lin

For the past year, Su Lin has been the primary subject of our giant panda hearing study. About six months ago, Zhen Zhen began her participation in earnest, and for the last two months, she has been showing us what a three-year-old panda can hear. Data that we’ve collected from both of these bears are unprecedented and mark the first glimpse into the auditory world of the giant panda.

While keepers are working hard to make sure Su Lin and Zhen Zhen are ready for their upcoming adventure and transition to life at the Bi Feng Xia base in Sichuan, China, our research team is also working hard collecting every last scrap of data we can on this pair! Our hearing study requires a collaborative effort between researchers, keepers, and bears, and very few other facilities anywhere in the world have the combination of resources that allows the pursuit of such research. We are very proud of our collaborative efforts and are going to miss working so closely with Su Lin and Zhen Zhen.

We began the hearing study on giant pandas about two years ago, with Bai Yun as our main subject. In the month before she gave birth to Yun Zi, Bai Yun decided that she wasn’t interested in our research anymore! Of course, we obliged her desire to be left alone and shifted our focus to Su Lin; she showed us her hearing was perhaps even more sensitive than that of her mom. Over the course of the last year or so, we have been able to collect a lot of data on Su Lin and, when our analyses are complete, we should be able to produce a comprehensive description of panda hearing—an unparalleled achievement.

Unfortunately, we haven’t had as much time to work with Zhen Zhen, but we have been able to pinpoint some important frequencies to test, and her data will make a very interesting comparison: Zhen Zhen’s young ears are in perfect shape, but are her listening skills as sharp as her older sister’s? Again, when the analyses are complete, we’ll have more answers.

Over the next week or so, we will work with Su Lin and Zhen Zhen as much as we can. The data are, of course, important, but the time the keepers and researchers get to spend with the bears is something to cherish.

After Su Lin and Zhen Zhen leave San Diego, we will reintegrate Bai Yun into the study and incorporate Gao Gao as well. Gao Gao has been working with keepers and getting ready to be a part of the study for some months now, and we are all looking forward to having a chance to work with him and study his ears as well.

Megan Owen is a conservation program specialist for the San Diego Zoo Institute for Conservation Research. Read her previous post, New Chapter for Su Lin, Zhen Zhen.

196

New Chapter for Su Lin, Zhen Zhen

Su Lin

When Bai Yun and Shi Shi arrived in San Diego from China in September 1996, the San Diego Zoo made it clear that it was committed to giant panda conservation. Bai Yun and Shi Shi captured the public’s attention, and the problems we encountered trying to get this mismatched couple to breed mirrored the predominate conservation problem that researchers were trying to tackle at facilities in China: How do you get giant pandas to breed in a captive setting? How do you get pandas to do what should come naturally?

Over the next 10 years, our interdisciplinary panda team worked tirelessly to study all aspects of reproduction, apply what we learned to the pandas at the San Diego Zoo, and develop a two-way exchange of knowledge with our partners at the Wolong Breeding Center in Sichuan, China. In 1996, only two females gave birth at Wolong. Although captive breeding was only one component of the conservation puzzle, it was clear that without a self-sustaining and genetically diverse captive population, the ultimate goal of reintroducing pandas to the wild would never come to fruition. But how quickly things have changed!

By the time I traveled to Wolong for the first time in the winter of 2000, the breeding center was enjoying a record-setting number of recent giant panda births (11 cubs!), and the San Diego Zoo’s Hua Mei, conceived through artificial insemination, was charming Zoo visitors and giving us a lot to study in the realm of panda cub development. The studies of panda behavior, reproductive physiology, genetics, and animal husbandry had all come into play to support the success at the San Diego Zoo, as well as at the Wolong Breeding Center.

Over the years, we (the Zoo’s Panda Team, visitors to the Zoo, and panda fans) have developed an incredible connection to and love of the pandas that have been born and raised in San Diego. Hua Mei’s departure from the Zoo marked our first experience with sending a San Diego-born panda to China. She was followed by Mei Sheng in 2007. Although we all knew it was for the best, it was a tough pill to swallow, and Hua Mei and Mei Sheng were sorely missed. Looking back now, however, with seven cubs representing Bai Yun and the completely unrepresented Shi Shi’s genetic make-up, we are very, very proud to have contributed to the broader needs of giant panda conservation.

Zhen Zhen

Soon, both Su Lin and Zhen Zhen will follow in older siblings Hua Mei and Mei Sheng’s footsteps. As I write this, I can tell you that I will miss these two bears! Su Lin is five years old, has already experienced her first fully developed estrus cycle, and is more than ready to join the conservation breeding program at the Wolong Nature Reserve Giant Panda Bi Feng Xia Base. Zhen Zhen is three years old now and will embark on her panda adolescence as part of the panda program at Bi Feng Xia as well.

Both Su Lin and Zhen Zhen have made incredibly valuable contributions to our research program and have contributed ground-breaking data on panda hearing sensitivity. These data will allow us to better estimate how noise from human activities may impact giant pandas in the wild. Collecting these data allowed keepers and researchers to work with both of these beautiful bears, up close and personal, on a daily basis. What a pleasure that has been!

As the drive to learn conservation-relevant knowledge of giant pandas shifts from captive propagation to reintroduction, we are excited that the pandas of San Diego will become a part of this larger conservation effort. Who knows? Maybe in the not-too-distant future, one of Gao Gao and Bai Yun’s descendants will one day be born in a large, old-growth tree den high in the mountains near Wolong. That image alone is enough to bring a smile to my face and makes me truly feel that the Giant Panda Team, and supporters of the San Diego Zoo’s pandas, have much to be proud of.

In preparation for their new adventure, Su Lin and Zhen Zhen will not be in public view beginning Monday, August 16, while they continue a training program that helps prepare them for the changes ahead. Their mother, Bai Yun, and her one-year-old cub, Yun Zi, will continue to be seen at the San Diego Zoo.

Megan Owen is a conservation program specialist for the San Diego Zoo Institute for Conservation Research Read her previous post, Birthday Celebration.

202

Yun Zi: 10 Months

It’s about time for an update on our little guy! Now 10 months old and weighing in at 41 pounds (18.8 kilograms), Yun Zi is an easy-going panda youngster that sleeps during a good part of the day and is quite active at night, as many of you have observed on the San Diego Zoo’s Panda Cam.

This morning, I chatted with one of our panda narrators, Kay Ferguson. The first thing she told me was that Yun Zi is NOT a morning bear. These days he will often sleep, waaay up in the trees, until 2 p.m. or so, unless Bai Yun wakes him for a feeding. But how does she wake him when he’s up so high? Kay explained that Bai simply stands under the tree and calls to him, making a bleating sound. The panda pair has access to their bedrooms at night, but they don’t always sleep together. Sometimes Bai Yun retires to the bedroom for a nap, leaving Yun Zi to snooze in his favorite treetop perch.

The cub is still nursing, and when he gets hungry, he seeks out his mother. However, in Bai’s opinion, a fresh delivery of bamboo often trumps feeding her cub, at least for a few minutes. Yun Zi has learned to be patient—Mom will be available shortly! Fortunately for him, there are also carrots, yams, leaf eater biscuits, and apples (a favorite with both mother and son) to enjoy. Yun Zi is also practicing his bamboo-eating skills, but right now he’s still at the nibbling stage of the process.

Another new skill Yun Zi is working on is scent marking. Whenever he sees Bai make a scent, he comes dashing over to sniff it intently, rub it all over his little body, and place his own scent on top of it. This can often keep him quite busy. When he was nine months old, Kay noticed Yun Zi scent marking using the “handstand” technique, just like his father does!

And of all the new toys the pandas received, his favorite one so far is the floating platform (pictured at top). Surf’s up!

Debbie Andreen is a blog moderator for the San Diego Zoo.

230

Estrus Peaks and Valleys

Bai Yun watches Yun Zi's antics.

In recent years, Bai Yun has displayed behavioral signs of estrus in an unpredictable pattern. The pattern of expression has been very truncated, encompassing a few short days of intense behavior alerting us to her mating readiness. This has been a change from the pattern of her younger years, in which the behavioral trends in her estrus were more lengthy and signaled well in advance that her body was preparing for mating.

When she first arrived at the San Diego Zoo in 1996, Bai Yun was a young adult bear. She had an annual estrus the first three years, until daughter Hua Mei was born. During that time, we would see an increase in scent marking about two weeks prior to ovulation, and an increased restlessness would set in. Why might a female undergo such changes so far out from her breeding window?

Recall that in the wild, pandas maintain overlapping home ranges. In those home areas, the bears are generally solitary as adults. However, they are exposed to the scents of other neighboring bears that have crossed over their path days or weeks before. If a female is a few weeks out from peak receptivity, it makes sense that she would need to begin to advertise her status to any males that might be in the area. She scent marks, and a male who comes across her scent a few days later can recognize the change in her status via that scent mark. Our research in Wolong has confirmed that males are more interested in scent from a female who was known to be in estrus at the time she left the scent. Once he has identified this change in a female’s status, a male will then likely remain closer to this female, assessing her status more frequently and keeping closer tabs on her in order to be present at the time for mating.

A younger Bai Yun has demonstrated that about a week prior to her peak, her rate of bleating begins to climb. This friendly, goat-like vocalization picks up at a time when males in the area are likely to be closer than usual, thanks to her increased scent marking. Within a few days of her peak, she increases her rate of chirping, a sharp, louder vocalization that we can often hear through the doors and windows of our building! Recent research from our collaboration with Zoo Atlanta has revealed some interesting information about these vocalizations and how they relate to male-female interactions: it appears males can use elements in the chirp to identify the precise time when a female is most fertile. Thus, when a male that has been hanging around waiting for his opportunity to mate hears his female chirping, he can assess whether or not she is ready to breed yet.

I have often wondered about Gao Gao’s ability to assess Bai Yun’s readiness for mating. Even with a truncated estrus in the last few years, and limited exposure to her scent, he seems able to pinpoint the time to breed with her. The next day, despite her willingness to breed again, he may often show no interest. Perhaps it is a change in the sound of her chirp that he is assessing and determining that it is not worth his effort to endure another breeding encounter. For a wild male, following a female closely can be an energetically costly endeavor: he risks coming into close contact with other males, and fighting may result. The process of mating itself is laborious and may take up most of a day or two, leaving him physically drained. If a female turns on the male during courtship, he could be injured. And all the effort in assessing and breeding with her detracts from his feeding schedule. Thus, it would seem that making judicious choices about when to push his luck could be advantageous to a male panda.

Why am I discussing this now, when Bai Yun is sure to experience a lull in her estrus cycle due to the fact that she is still nursing Yun Zi? Because, despite Yun Zi, we have an estrus in progress in San Diego: this time, with Su Lin. Unlike her little estrus last year, our young bear (four years old) appears to be experiencing a more adult-like, full-on estrus. She is deep into the scent-marking stage, complete with restlessness. Bleating has begun, and chirping should be on the horizon soon. This is likely her first fully fertile estrus, as females in Wolong have been bred at her age, resulting in a birth a few months later. However, Su Lin will not be breeding here, since she clearly cannot breed with her father Gao Gao. Nonetheless, this is an opportunity for the public to observe a full, lengthy behavioral estrus in a panda female, something we haven’t seen around this facility in many years!

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

Here’s the most recent chart comparing our panda cubs’ growth during their first 200 days:

151

Morning Ritual for Yun Zi

panda_yz_1-12-10aAs we come to the end of January, people are coming from near and far to see our Yun Zi. Unfortunately, he’s not always the most active little boy you’ll see. What a lot of people don’t know is that he’s been awake and playing for about three and a half hours already by the time the San Diego Zoo opens at 9 a.m.

As keepers, we get into work at about 6 a.m., sometimes earlier, and the first thing we do is check our bears using the monitors that we have in the Giant Panda Research Facility building. We’re looking for where they are and what they’re doing. Normally, we find Bai Yun and Yun Zi either in the den, playing, or in the garden room with Bai eating while Yun Zi practices his climbing skills. This is where we see him burn off a lot of that energy, and it’s important for him to keep climbing and building up those leg muscles.

Around 6:30 a.m., we start getting the classroom exhibit ready and begin to encourage Bai Yun and her cub into the exhibit. Breakfast has been laid out for Bai Yun and enrichment has been put out to try and keep Yun Zi active. One thing I love about this cub: we can put out as many enrichment items as we want, but at the end of the day, the enrichment he gets excited about the most is a dried-up leaf!

Bai Yun is always willing to come out of the bedroom; she knows there’s breakfast out there. But the cub is more about instant gratification rather than walking a little bit for some fun. It can take us anywhere from a few minutes to sometimes half an hour to get the cub out of his back bedroom area. Once in the tunnel that connects to the exhibit, he’ll follow mom quickly, but getting him to the tunnel can be a little challenging. “Patience is a virtue,” but in our line of work, “patience is our job.”

Once out on exhibit, he usually spends some time playing with his enrichment and making a mess of Mom’s bamboo that we have laid out for her. After exerting all his energy, he’ll climb up the tree, find a good, comfortable spot, and go to sleep—and that’s often at 9 a.m. and the Zoo opens for the day.

So come by and check him out, but please don’t be too upset if he’s sleeping. After all, it’s tough work being cute!

Anastasia Horning is a panda narrator who often helps out as a keeper at the San Diego Zoo

0

Like Father, Like Daughter

Zhen Zhen

In my blog post about my time as a keeper (see Pandas: From Both Sides), I had mentioned that Zhen Zhen exhibited some behaviors that were very similar to her father, Gao Gao, and she’s still surprising me. Typical behaviors that I’ve seen are mainly shown right around when she’s about to be fed: when the keepers call her to come inside, she won’t come right in; most of the time she’ll do another lap around her enclosure and then make her way into her bedroom. And then there are her eating habits: she’ll move bamboo far away from where it is put down, and once she’s comfortable she won’t move for anyone.

Zhen Zhen herself has a certain calmness about her that I think resembles her father more than any other cub. Very rarely does she get surprised by sounds from the crowd, and she is more than content with a piece of bamboo to keep her occupied. I think the only real time that I see her run around or even vocalize is when she is getting ready to be fed, just like her father. Gao Gao has always been a rather quiet bear, and I think that Gao Gao finally has a cub who might take after him.

Male giant pandas have no knowledge of their offspring, nor knowledge if breeding was even successful, and Zhen Zhen wouldn’t have picked up these behaviors from her mother since Bai Yun doesn’t do any of them. Zhen Zhen does show some behaviors similar to her mother as well, but that’s understandable, since she spent the first 18 months of her life with Mom.

When Zhen Zhen comes out for her evening feed, for some reason (and there isn’t a good explanation for it) she will promptly sit with her back toward the crowd and ignore them while she eats. This has been happening since the beginning of summer, and at first I thought it could be a way for her to have some privacy, or de-stress from a long day, but I noticed even on days where it’s been really quite here she will turn her back. I remembered that Bai Yun does the same thing when she goes on exhibit, and I have a feeling that our little Zhen Zhen may have picked up the same behavior.

Another behavior that panda observers, narrators, and guests love to watch for is the girls tapping their paw. Both Zhen Zhen and Su Lin tap one of their back paws as they fall asleep, and they are usually draped over a tree branch when they are doing it. When they first go up the tree, you can see it tap very often, and as they start to drift into sleep the tapping gets less and less frequent. I have always looked for this particular behavior in the kids because I know exactly where they get it from: their mother, Bai Yun. She taps her paws as she goes to sleep no matter where she happens to be. I’ve seen it when she’s on a flat service or when she’s hanging her foot down somewhere. Several of our observers think it’s funny to watch the kids perform this behavior, and when we watch them we all wait for the foot tapping.

Keep watching the Panda Cam for activity of our little boy, and I hope to see you at the panda exhibit real soon!

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

208

Panda Cub Care

panda_exam6_1Hello again, panda fans! It seems that the birth our newest cub has sparked the interest and curiosity of people all around the world. An increasing number of people are calling the San Diego Zoo, sending letters, and posting questions on our blog site. Never fear, your favorite keeper is here (humbly, of course)! Your questions range from “How is Bai taking care of her cub?” to “What was Su Lin doing on the Panda Cam the other morning?” It’s a wide scope and I won’t be able to answer all of them at once, but I will do my best.

First and foremost, Bai Yun is being a wonderful mother, as always. This is my first time with a panda cub, so I’m nervous every time she covers him with bamboo or leaves him on the floor of the bedroom; but Bai is an experienced mom, and she knows what she’s doing. Like any mother who’s had multiple offspring, Bai seems to become more confident in her parenting skills with each cub. When Hua Mei, her firstborn, was a cub, Bai was right there to check on her and to hold her every time she squeaked or moved. With her fifth cub, Bai knows that if she feeds him at a certain time, he’ll fall asleep long enough to let her eat a good meal.

Several people have asked about the bamboo nest in Bai’s cubbing den. Part of being a good mom is providing safe shelter for your offspring; the nest in the den is Bai Yun’s handiwork. About one month before a cub is born, Bai is given access to her birthing den. Keepers cut her normal bamboo diet into 2- or 3-foot lengths (instead of the usual 5- or 6-foot lengths), short enough for her to comfortably carry into the den. In the few weeks before she gives birth, Bai Yun shreds and arranges bamboo to make a soft, warm nest for her cub.

We keepers glance into the den opportunistically to inspect her work. We pull out extra-thick pieces or anything that looks like it’s dangerously sharp. Bai Yun does a wonderful job nest-building, though, and most of her work is left untouched. This is why the bamboo in the den looks dry: once the cub is born, she discontinues her nest-building and focuses all of her energy on feeding her cub and keeping him warm. Bamboo is very low in nutritional value, and a panda can really only afford to focus its energy on one task at a time. This is especially true with mother bears, which do not leave the den for any reason (including eating and drinking) for days at a time before and after the birth of a cub.

When a cub begins to grow, when it begins to nurse and subsequently nap regularly, and when it has its own hair to keep itself warm, the mother can leave the den long enough to eat or drink. Her appetite slowly increases. At first, she eats only one or two bites before returning to her den. However, it has been many weeks since the birth of Bai Yun’s boy, and she is now eating almost at much bamboo as she was during the middle of her pregnancy. She leaves the cub alone in the den to take a good nap while she eats. The cub is now 21 inches (52 centimeters) long, and the little den is getting to be a bit crowded with both Mom and baby in there, so sometimes Bai takes her own naps outside of the den.

Once the cub starts to get larger, Bai will move him outside of the den to encourage him before he’s mobile enough to follow her and leave on his own. At this point in time, even if Bai Yun leaves her cub alone in the den, if he makes one little squeak or cry, Bai immediately stops whatever she is doing. Her ears perk up, she turns toward the den, and attends to her cub.

I hope this information helps. I’m very excited to see how many people read these blog posts and watch our pandas every day. Thank you for your curiosity and for your interest. One of the most important things a keeper can do for their animals is to educate others and to, hopefully, inspire them to learn about and to help the species (in this case, endangered species) that need us.

Juli Borowski is a keeper at the San Diego Zoo.

Here’s video of the cub’s 6th exam.