(Page 2 of 4)
Unlike polar bears and grizzlies, which travel long distances to find food, pandas can stay close to home. “Essentially, they’re living in their own salad bowl,” says Edwards. But the animal’s diet also makes it vulnerable to bamboo die-offs, which occur naturally every 40 to 100 years after the plants flower. In the past, when one bamboo stand died, pandas simply migrated to another. But most of the species’ habitat has been destroyed or fragmented, threatening to strand the bears.
The giant panda’s dependence on bamboo may even help explain its unusual reproductive system. When a female becomes pregnant, the fertilized egg does not immediately attach to the uterine wall, as it does in most mammal species. Instead, the embryo floats within the reproductive tract for many months, attaching only about 45 days before the cub’s birth. Edwards suspects a female cannot build up enough nutrients from bamboo to support a fetus for any longer. As a result, newborn cubs have only just begun to develop. Pink and hairless, they weigh about a quarter of a pound, or the same as a stick of butter. (Hence Tai Shan’s nickname, Butterstick.) Compared with the size of the mother, “no other non-marsupial mammal has a smaller offspring,” says Edwards.
Pandas give birth to twins about half the time. This itself is not unusual—most bears have twins or triplets—but a panda mother usually selects one of her two cubs to raise and lets the other die. Biologists once believed that such an apparently illogical act occurred only in captivity. But in fieldwork conducted at Wolong Nature Reserve in the late 1980s, biologist Pan Wenshi often found a dead cub near a mother that was caring for a healthy one. Scientists speculate that new panda mothers just can’t afford to feed two cubs—another behavior that may be an evolutionary adaptation to the animals’ low-energy diet.
Tai Shan’s story begins in 2000, when his mother, Mei Xiang (may-SHONG), and father, Tian Tian (t-YEN t-YEN), came to the National Zoo on a ten-year loan from China made possible through major sponsorships by Fujifilm and Animal Planet and other donors. (Three other U.S. zoos—in San Diego, Atlanta and Memphis—also host pandas; in exchange, each institution must contribute at least $1 million per year to panda conservation in China.) In 2003, as the bears were just reaching sexual maturity at ages 5 and 6, they mated for the first time, but no pregnancy followed. The next year, after the pandas tried unsuccessfully to mate on their own, Zoo scientists inseminated Mei Xiang with Tian Tian’s sperm, again without conception.
Last spring, as Mei Xiang began to show signs that she was coming into estrus, the scientists prepared to place Tian Tian’s sperm directly into her uterus. Because the procedure would require Mei Xiang to undergo general anesthesia—which always carries a risk—they decided to try the insemination just once, a considerable gamble given how briefly a female is fertile. “In China, we learned just how narrow the window of opportunity is,” says JoGayle Howard, who performed the procedure.
Recent studies have fine-tuned techniques to predict that 24- to 48-hour period. One is to analyze vaginal cells. In exchange for a reward—a biscuit, apple or pear—Mei Xiang has been trained to enter her 5- by 4-foot training cage and submit to all manner of pokes and probes. Zoo technicians examine cells swabbed from her vagina to tell how close to ovulation she is. They also siphon her urine off the enclosure floor. National Zoo endocrinologists Steve Monfort and David Kersey analyze these samples for changes in estrogen levels.
The big day turned out to be March 10, 2005. Earlier that week, Mei Xiang had increased her frequency of “scent marking,” or rubbing a gland near her tail against the ground to deposit a sticky substance with an odor detectable by other pandas. Zoo scientists were monitoring her urine and vaginal cells round-the-clock. When tests showed Mei Xiang was ovulating, they first gave Tian Tian an opportunity to do the job himself. But after 24 hours—during which he “hadn’t achieved the proper alignment,” says assistant curator Lisa Stevens—the scientists took over.
To get Tian Tian’s sperm, the researchers anesthetized him and used an animal breeding technique called electroejaculation, in which a probe inserted into the male’s rectum produces electrical stimulations that cause ejaculation. For the insemination, Howard used a modified laparoscope (a tiny telescope with a fiber optic light often used in human medicine) to guide a catheter through Mei Xiang’s cervix and into her uterus. “We felt the timing was right on,” says Howard. “The procedure couldn’t have gone faster or more smoothly, and that’s what made me nervous.”


Comments
dear scientics,curators,and keepers i want to let you know what a good spot the panda cameras would like to celebrate in puerto rico i am crazy in love with mei xaing, tai shan and tian tain what fantastic job you,re were doing and what a difrence you were making thank you so much and make me a god bless you all and a merry chirstmas to you all love adriana p.s i want to adopt a giant panda
Posted by adriana on December 17,2007 | 07:24AM
hey im 12 and im doing a report on tai shan...does any1 know his exact weight when he was born? im havin trouble
Posted by darien on January 10,2008 | 03:58PM
I loved looking at the photos of Tai Shan. I love pandas and can't stand thinking about the problems they face. I hope they can find a mate for Tai shan and have a cub of their own
Posted by Madison Neil on February 21,2008 | 09:02PM
Wish Tai would never have to be sent to China. I am going to miss seeing him on the cam. I have seen him grow from being a baby to now going on 3 years old. He has been a joy to watch everyday. I love the way he circles round and round his yard looking for goodies. Wish I could visit the zoo someday and see him in person but I know that will never happen so he will continue to bring me much joy on the cam until he has to go to China. Hope you will be updating us on him while he is living in China. Thanks. It will be appreciated. I wish him the best while he makes his life in China. I love you, Tai. Boun Voyage to China. Happy BIrthday in July, sweetie.
Posted by Marie on March 28,2008 | 12:24PM
A question. Do pandas in the wild eat during the night?
Posted by Sue on May 2,2008 | 04:54PM
I love Panda because they are so cute (I think ,they are most lovely animal on the world)
Posted by Donchanok on June 20,2008 | 03:59AM
I am now only being introduced to the magical world of pandas. I hope Tai Shan will not be sent back to China, anyway, they were able to breed lots of baby pandas over there and giving Tai Shan to the US would not hurt them. Tai Shan now has a home and it would be a pity to send him back to China. I am appealing to the Chinese government to have a heart
Posted by Elanore Seeta on June 25,2008 | 05:46AM
Elanore what you are asking sounds reasonable to me. But an agreement would have to be kept I would think. Tai Shan will be missed by all that have followed his growth. He will be the darling of China. I will continue to keep watching him on the cam until the day he will no longer be with us. I know that I will shed some tears as I am sure that his keepers will too and all the staff involved in the raising of Tai.
Posted by Marie on June 27,2008 | 12:08PM
What exactly is meant by the turm "paw licking?" In the daily log by the panda keeper they refer to Mel Xlang as doing a lot of paw licking. Is this a sign of confirmed pregnacy?
Posted by Amy on July 27,2008 | 01:46PM
My greatest pleasure is watching the Pandas on the cam, I was thirteen when I first fell in love with them, I am now sixty four and still in love with them, I will be going out to see them in November. How lucky I am to others But this may be my last chance to see them.
Posted by Susan Wells on September 5,2008 | 03:08AM
Thanks so much for those who don't get to travel but get to watch the cam. All 3 pandas are just wonders of the world. Tai Shan is 3 years old and I understad that the Chinese government has agreement to take him away to China. But if you'll just ask people every where you'll get the general consensus that it's only fair for Tai Shan to stay at the the national zoo in D. C. for longer time. I know you observe him and you'll know whether or not he'll have any indication for readiness to breed. Well, there's the female 3 years old in San Diego. Please plea to the Chinese government to let these two meet and see if they'll mate. Then when China gets this union of the panda family to China, it would be just so precious and a all Chinese American panda family. That should be an appearling proposition. Will the two zoos work up an arragement with the Chinese goverment? I know the 2 panda parents are from 2 different reserves in China, but since they are both from the same province the 2 breeding centers ought to work out an agreement for these pandas. Please let the Americans and visitors enjoy the pandas a little longer! When we have time and can afford it we'll make trips to China to see them too as I have done so to China and visit the Pandas. Will you please advise us where to write to the Chinese to plea this case, please? Much Thanks, Anita
Posted by Anita C. on September 9,2008 | 10:12AM
I don't think that they will mate Tai with the 3 year old in San Diego because they are cousins both mothers have the same grandfather. Tai, Su LIn and Chen Chen resemble each other, don't you think?
Posted by Marie on September 11,2008 | 11:59AM
It is only another three more weeks for me to see the Pandas, and this is one of my big goals in life. I feel the same about Tai staying where he is, why move him as enough breeding is going on in China,and have they been able to release any Pandas back into the wild? I don't think they have. Please can you let me know if I am right or wrong. Susan Wells 2/11/08
Posted by Susan Wells on November 2,2008 | 03:50AM
I too will grieve the day that you have to send precious Tai to China. Since the earthquake's disruption of the work at the Wolong site, it seems the best thing for him will be to stay in the US. I watched him for 2 years, from the day his was born and fell in love. Now I've decided I definitely want to go to China to see and hopefully work with the Pandas for my 70th birthday...only 7 years to save up! Please keep him here...I know there must be some way. Maybe the new President can help! Thanks for these wonderful past 3 years......
Posted by Mary Rafter on December 23,2008 | 03:46PM
i came to the zoo last year and met the pandas. i love to watch the panda cam. i am 6 years old and want to be a panda doctor one day. thank you. clay
Posted by clay coleman on February 14,2009 | 07:00PM
I love those beautiful animals so much that I can't bear to think of them being sent into the wild after being taken care of so well by the great care takers there at the National Zoo, Lovingly, Mary F. Winke
Posted by Mary F. Winke on August 17,2009 | 02:18PM
I fell in love with Giant Pandas while watching Tai as a cub just learning to crawl and I fell in love with Tai Shan in a big way. Tai is very very special!!
I watched him a LOT through his first 2 yrs.
If you just can't get enough of him from the cam, or if you missed those early yrs, I highly suggest going to flickr.com and looking at the thousands of photos there.
Almost every moment of his life is there captured in brilliant photography. A great group with the best photos, I think, is Pandas Unlimited. You won't be disappointed with thier spectacular photos and videos.
Posted by Connie on October 31,2009 | 07:48PM