The Cub's 20th and 21st Months
April 5: Mei Has Been Artificially Inseminated
Zoo scientists and veterinarians have performed two artificial inseminations on Mei Xiang. The first procedure took place yesterday early evening, and the second occurred this morning. Mei was inseminated under general anesthesia with thawed semen from Gao Gao, a male giant panda residing at the San Diego Zoo.
As described in detail in the March 27 update, genetic analysis by Zoo scientists showed that Gao Gao is more genetically valuable than Tian Tian. Mei also is genetically valuable. Breeding Gao Gao and Mei will increase the proportion of valuable genes in the captive population, thus contributing to future genetic diversity. more
The Zoo's reproductive scientists have spent years perfecting artificial insemination techniques on giant pandas. Tai Shan was the result of an artificial insemination procedure conducted in mid-March 2005. This week's procedures mark the first time panda semen was shared between institutions in North America.
Zoo staff will continue to monitor Mei’s hormone levels and conduct ultrasounds to determine pregnancy. Female giant pandas undergo pseudopregnancies when they ovulate but fail to conceive. During a pseudopregnancy, hormonal changes and behaviors are identical to a true pregnancy, which makes it very difficult to determine if a panda is pregnant. It could be three to six months before a cub would be born.
March 30: Mei Is in Early Estrus
>We separated Mei Xiang and Tian Tian on Tuesday afternoon, March 27. Analysis of hormones in her urine as well as vaginal cytology studies confirmed that Mei is in early estrus (also called "periestrus"; learn more about this.) On Monday afternoon, we became aware that Mei’s estrus was imminent, based on Tian’s increased intensity and persistence in interacting with Mei. Tian was very interested in approaching Mei’s rear, as well as in standing on her back in some rather haphazard mounts. Mei was not at all pleased with this special attention! She swatted him several times and ran away from him.
On Tuesday, everything was quiet again until the afternoon when Tian again began to pursue Mei with renewed intensity. Tian rushed at her again with his ears forward, only to stop abruptly when she turned to face his advance with a moan or sharp bark. Tuesday afternoon we also noted that Mei’s genitalia were starting to swell and redden, which along with increased scent marking, are the observable signals of the onset of her heat.
Tuesday was a very warm day so after their intense interactions we had to hose both pandas to help them cool down. Normally the hose elicits play from them, but not on this day. Mei preferred to just sit in the puddles to cool down. Later, both completely ignored the fruitcicles we gave them. Eventually, however they did settle.
Since the separation Mei has been very mellow but Tian remains very restless. He has been power walking around the exhibits, scent marking and bleating in full breeding rut. Enrichment and training distract him only briefly. It is a real challenge to keep Mei and Tian as far apart as possible so that Tian does not have to come in contact with her message-laden estrous scent marks. Now we are actually thankful that a female panda’s period of sexual attractiveness and receptivity is so short!
Tai Shan continues to be Mr. Independent. He holds court daily, all 115 pounds of him, by the glass of the new habitat opposite the giant salamander exhibit. He rests alongside the water-chilled rock, and strips his bamboo meals, chewing with his eyes closed and mouth open. He has not seemed to notice all the hormonal intensity next door.
On some days we get calls that “the red pandas have escaped and are in with the giant pandas,” as their exhibit is also across from this side of the panda habitat. It is not unusual to see a red panda bouncing along on a limb, seemingly right above Tai Shan! Don't worry, the red pandas cannot get out of their exhibit.
Thank a million to the members of Pandas Unlimited who have donated funds for our pandas. We installed three large saw-toothed oak trees this week to provide new climbing trees for enrichment, as well as to enhance the old exhibits. The poor old majestic willows are now just mere ghostly stumps. The new oaks’ trunks are about six to nine inches in diameter and their height ranges between 18 and 25 feet. We choose this tree species because it is sturdy and faster growing than other oaks, and the rough bark seems to hold up to panda claws. It also is found in their native habitat. We greatly appreciate your generosity.
As part of our giant panda research program and to strengthen genetic variability among zoo pandas, we are planning to artificially inseminate Mei Xiang with semen from Gao Gao, San Diego Zoo’s adult male panda, should Mei display estrus this spring.
Maintaining genetic diversity is important to the long-term viability of animal populations. When zoos breed endangered species, one factor they use to decide which animals to pair is something called a mean kinship figure, which represents the number of living relatives a particular individual has in the zoo population. We have learned from genetic analysis conducted by Zoo scientist Jon Ballou that Gao Gao is a genetically valuable animal with a low mean kinship number. Mei Xiang also has a low mean kinship number and is genetically valuable. Breeding these bears will contribute to future genetic diversity.
Gao Gao has had two offspring with Bai Yun at the San Diego Zoo—three-and-half-year-old Mei Sheng and one-and-a-half-year-old Su Lin. The zoo plans to pair them again this year.
Tian Tian has a high mean kinship number—his genes are over-represented in the zoo giant panda population, which makes him a low breeding priority. Breeding Tian and Mei would combine over-represented genes with valuable genes, diluting the valuable genes and decreasing genetic diversity in the future population.
March 13: An Independent, Confident Little Bear
Tai Shan is now spending his nights in the new indoor exhibit. It took him a while to decide on a comfortable spot in the new rock work, but he finally settled on a few choice places.
Tai continues to impress us with how easily he has adjusted to this new phase in his life. Almost all of the cubs reared in China's breeding centers are weaned by six months. The needs and experiences of cubs weaned at this age are very different from cubs that are separated at 18 to 24 months. These older cubs have already spent much of their time naturally separating from and being pushed away by their mothers.
Tai Shan exhibits the independence and confidence of a well-adjusted little bear. There have been a few instances of Mei and Tai calling back and forth and looking for each other. The rest of the time, and to our great relief, they go about their daily panda business, relaxed and content. These slightly more stressful instances have occurred in the morning when the pandas are also very anxiously awaiting their shift into the outdoor yards and fresh bamboo. It is difficult to tell how much of their behavior is built upon their already-needy state early in the morning. If either Mei Xiang or Tai Shan vocalized during this time, this would set off more directed calling between them.
Mei and Tai are now housed on opposite ends of the habitat for now. Once we are through this weaning period, we plan to provide mesh access, and eventually permit some socialization between Mei and Tai. Tai also has the opportunity to interact through mesh with Tian Tian during shifting, especially in the transfer chute areas.
When the keepers arrive in the morning they cannot get everyone fed fast enough. This is the time of the year when pandas go through bamboo like Bugs Bunny chows down on carrots.
Tai Shan weighed in on Sunday at 112 pounds! Tai is shredding the largest culm, or stalk, just like an adult. When the bears are all finally satisfied, it is usually time for rest or other pursuits, if only briefly, before they are ready for the next fresh delivery. Around this time of year we look forward to the slower, and much lower appetite, days of the hot summer months.
Tian and Mei are together again during the day. Although they are not physically interacting very much, giving them the option and the associated choice of avoidance tactics, seems to occupy the ever-restless Tian.
Tai Shan spends his awake time exploring the outdoor enclosure and playing. Like the adults, he seems to enjoy tumbling and rolling off the limbs and down the hills. He has had fun with a couple of new toys. One is a “jolly ball,” a ball with a handle that Tai used recently in an attempt to carry it into one of the trees. Tai also was given two new “weeble” toys, thanks to two of his fans. These toys are shaped like giant medicine capsules, and are weighted at the bottom so that they tip and bob around. The smaller one, about 18 inches long, was subjected to a lot of rearing and pouncing.
Tai also has been doing very well with his training sessions. He has learned to present both his paws, even though like the adults, he is very left-pawed when he holds bamboo. He has also learned to grasp a metal rod and put his arm into the sleeve we use for drawing blood. He is like a sponge, soaking up every training task we present to him.
The panda staff want to reassure everyone that Tai Shan is adjusting smoothly to all the changes in his life. We monitor him closely and care enormously about his well being. As we manage this stage of Tai’s life, we recall his past 20 months with tremendous nostalgia, thankful for an amazing experience. We have learned so much and are better prepared for the future, because of our experiences with Tai Shan.
Only three other panda cubs have been weaned at this age, all at the San Diego Zoo. Only two mothers have been involved. We are contributing to a collaborative database of information on how to best wean cubs, mother and cub behavior during weaning, and metabolic and hormonal changes in female pandas related to the cessation of lactation. We hope you've been enjoying learning about pandas, too.
February 27: Tai Keeps Growing Up
Panda cubs in the wild leave their mothers at about one and half years of age. Tai Shan is 19 months old, and has been living separately from Mei since February 22. Over the past five weeks, we have been gradually increasing the time they spent apart, in preparation for this separation. Everything has gone smoothly and we are pleased that both Tai and Mei are adjusting so easily.
Tai Shan’s weight has continued to steadily climb to a robust 107 pounds. He is always determined to do his part in depleting our daily bamboo supply! We are always ready with enrichment or training when any of our pandas is anxious. We have not had to do any more than what we routinely provide.
Since the separation, we have been able to give Tian Tian the opportunity to spend time with Mei. These sessions are following a pattern where Tian tries to solicit play and Mei proceeds to chase him away. It is great to see them get some good exercise, as they go running through the yards. They do eventually settle down to eat bamboo, and usually not very far apart. We watched Tian try to take Mei’s fruitcicle yesterday, but she was able to fend him off with one forearm, while managing to keep the fruitcicle tucked securely under the other forearm!
All the pandas now have the use of the new indoor enclosure. We were quite excited to give them access to this new area. The adults were very nonchalant about it, while Tai finds the smell of it, especially the scent of the prior passage of the adults, most fascinating.
The pandas also had an extended enrichment session this week due to the snow. A white wonderland descended over their world, turning the trees and logs into a painter’s perfect winter landscape. As each panda somersaulted in its own special places, the wet heavy snow frosted fur into a study of shadow and light. The juxtaposition proved that panda fur is definitely not very white.
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