MR. KOJO NNAMDIAnd you thought you had a weird day yesterday. Take a second to put yourselves in the shoes of Mei Xiang, the female giant panda at the National Zoo, here in Washington. She spent Monday afternoon receiving an artificial insemination. A quest for panda pregnancy that was live, tweeted in front of an online audience by the National Zoo itself, complete with its own hash tag.

MR. KOJO NNAMDIThere were tweets about straws of frozen panda sperm, panda ultrasounds, panda uterine walls and fake panda pregnancies, all with the hope that Mei Xiang will, frankly, get knocked up and give birth to another adorable panda cub that will remind us of Tai Shan, the panda who might as well have been the mayor of the National Zoo when he was born seven years ago. But all kidding aside, this week's procedure was guided by cutting-edge science, and against the backdrop of America's complicated relationship with the home country of the pandas, China. Joining us to talk about this by phone from Front Royal, Va. is David Wildt. He is the senior scientist and head of the Center for Species Survival at the Smithsonian National Zoological Park. David Wildt, thank you for joining us.

MR. DAVID WILDTThank you, Kojo. It's a pleasure to be here.

NNAMDIAlso joining us by phone from Front Royal, Va. is Copper Aiken-Palmer, head veterinarian at the Smithsonian Conservation Biology Institute. Copper Aiken-Palmer, thank you for joining us.

DR. COPPER AIKEN-PALMERHello. It's good to be speaking with you.

NNAMDIIf you'd like to join the conversation, you too can call us, 800-433-8850. Several producers of this broadcast were among those yesterday who following the stream about panda pregnancy from their computers having nothing better to do, you've been trying to get the pandas at the zoo to reproduce for some time now to no avail, and it's my understanding that you went forward with the attempt at artificial insemination trying to take advantage of the one or two days a year when pandas are fertile. How did you know the time was right this week, and why did you ultimately make the decision that artificial insemination was the way to go? Copper Aiken-Palmer, I'll start with you.

AIKEN-PALMERWell, it's a cascade of different physiological parameters that we monitor. So we pay close attention to what's happening with hormones, we look at behaviors, we also look at some of the changes that are happening with the panda herself, and everything was just pointing to that short 24/48-hour window, and that's what made us move forward. We also were lucky enough to have representatives from one of the breeding centers in China named Li Desheng, and he was very helpful in helping us time when exactly we wanted to do this.

NNAMDIThese pandas have made it work before. They gave birth to Tai Shan seven years ago. What were the problems this time around? Are they maybe just getting too old?

AIKEN-PALMERWell, the first time was actually artificial insemination as well, and, you know, there's a lot of things that we don't clearly understand about what makes artificial insemination work and what doesn't, and quite honestly, the rates are not a hundred percent for artificial insemination, but we got lucky and everything worked out very well through a lot of hard work for the first insemination. Unfortunately, we haven't had the success for the subsequent inseminations.

NNAMDIThe number again 800-433-8850. Are you among those who are following the attempts to get the pandas at the National Zoo to breed? What do you find appealing about the pandas? 800-433-8850. David Wildt, it's my understanding that this time around the sperm that was used was harvested from Tian Tian seven years ago in yesterday's procedure. How did you store it, and how did you determine that it might be effective?

WILDTWell, Kojo, the issue with our pandas is one of whether or not they are experiencing some fertility issues, and during the early years of their time at the zoo, we were able to see some normal behaviors in the female, and we were able to collect really good quality sperm from him in the years associated with the 2005 artificial insemination. So we know the sperm that was used yesterday was actually collected in 2005, so we know it's fertile because that's the year the Tai Shan was born.

WILDTSo it's stored in liquid nitrogen. We use a lot of the same procedures that have been developed for human infertility patients. We often steal a lot of ideas from our colleagues with human infertility patients. But at the same time, every species is different. So a Giant Panda male is a lot different than a human male, and so we have to do a little tweaking with all of our procedures.

NNAMDIIn case you're just joining us, we're talking with David Wildt. He is the senior scientist and head of the Center for Species Survival at the Smithsonian National Zoological Park. He joins us by phone from Front Royal, Va., as does Copper Aiken-Palmer, head veterinarian at the Smithsonian Conservation Biology Institute. If you have questions or comments about yesterday's artificial insemination, call us at 800-433-8850. The tweets and the photos you tweeted yesterday gave some interesting visuals, even the early ones.

NNAMDIYou wrote that just getting Mei Xiang into the room was a struggle. How many people were involved yesterday, and what role did each of you play? This time I'll start with you, David.

WILDTWell, this is a really complex dance. We have a whole list of animal keepers, curators, animal behaviorists, veterinarians, fertility specialists, specialists who do artificial insemination. Behind the scenes we have people who are of course monitoring the hormones. So all told together, there was probably a team of about 25 people yesterday who were playing a direct role in everything from coaxing Mei Xiang into the room to receive her anesthetic, to actually conducting the artificial insemination itself. And as Cooper indicated, we were very pleased to have our colleague, Le Desheng, from one of the world's largest breeding centers in China here.

WILDTWe constantly share information. We were delighted he made it in time, just, you know, about an hour or so before we decided to do the artificial insemination. So that timing was exquisite as well. We were very lucky.

NNAMDII read in today's edition of the Washington Post that there are concerns about whether inbreeding among pandas is going to result in dangerous genetic mutations. How do you work against that, Cooper Aiken-Palmer?

AIKEN-PALMERWell, interestingly, for the captive Giant Panda population, we have a lot of genetic diversity, and so for the species that we have, I would say that Giant Panda, that's probably the least one that we're concerned about inbreeding problems. We carefully monitor who's related to whom, and the breedings are all planned well ahead of time, and we actually have a lot of genetic diversity in the population for Giant Pandas. Now, in the wild, things are a bit more of a challenge and that's largely because of small habitat areas and fragmented habitats, but for the Giant Panda, at least in the breeding centers all over the world, inbreeding is really not something that we face similar challenges as we do with other species.

NNAMDI800-433-8850. What do you think is the basis of the appeal of the pandas at the National Zoo? Is it simply a matter of them being cute or something else? 800-433-8850. David Wildt, what do you think is the basis of the appeal and the fascination?

WILDTWell, I have to look at the Giant Panda, Kojo, as a biologist...

NNAMDIYes.

WILDT...and ever since I was in the -- as an undergraduate in the university, I was fascinated with the fact that the Giant Panda is only in heat for 24 to 72 hours a year, and I would challenge you to think of another animal that devotes so little time to sexual activity. The Giant Panda only uses about -- well, less one percent of its annual lifespan to actually have sex. So this is very appealing to us as biologists. Why the Giant Panda has developed that reproductive strategy. It gives us only that one opportunity every year to help that animal become pregnant.

NNAMDIYour own view of this, Copper Aiken-Palmer, the appeal of the panda? So many thousands of people were following you on Twitter yesterday.

AIKEN-PALMERFor me, the appeal is pretty similar to, you know, they're very niche animals. The only eat bamboo, but yet they're considered a carnivore-type of animal. So it's very unusual. They're also interesting in that they live only in the mountains of China, and they have very rugged habitats, and they spend a lot of time roaming those mountains all by themselves only coming together during the breeding season. And so to manage to find each other among those mountain-scapes during just a 24 to 48 hour period of time is pretty amazing, quite honestly, and I think they have sort of a charisma as well.

AIKEN-PALMERSo there's something captivating in watching them lay back, recline back and eat that bamboo, shred that bamboo that's thicker than my wrist at times, and there's something captivating about them too that sometimes I have a hard time putting my finger on it as well.

NNAMDIIn case you're just joining us, we're talking about yesterday's artificial insemination at the National Zoo of the panda. Our guests are is Copper Aiken-Palmer, head veterinarian at the Smithsonian Conservation Biology Institute, and David Wildt, senior scientist and head of the Center for Species Survival at the Smithsonian National Zoological Park. You can call us at 800-433-8850. Have you been following the attempts to get the pandas at the National Zoo to breed? What do you find appealing about this, or what do you find interesting about it? 800-433-8850.

NNAMDISeveral questions for you. I'll start this time with you, Copper. This email from James in Bethesda. "Where did butter stick go? Is he a dad yet? Are they trying to make a dad? What is Tai Shan up to these days?"

AIKEN-PALMERWell, actually, Tai Shan is just now becoming old enough to even be considered as a dad, and that's part of the reason why he went back to China. He has so much more potential for becoming a dad and contributing to the population back in China. I know that last year I was actually at the center where he lives, and he was sitting back eating bamboo just like all the other pandas, but I must say, in his facility he's got a pretty nice enclosure. His digs are pretty nice over there, so no doubt they're well aware he's our superstar for sure, and I think Li Desheng was talking yesterday that they're actually thinking about putting him with females soon. So perhaps next year, maybe even this year. I'm not sure.

NNAMDIDavid Wildt, when do you expect to know whether or not you've succeeded?

WILDTWell, again, one of the unique biological aspects of this particular species is that they undergo something we called delayed implantation, like many bears. So she has no doubt ovulated. We have hormonal data now to indicate that she's already ovulated, and then, assuming that fertilization occurred, that egg -- fertilized embryo, actually floats in the uterus for a very long period of time, from 70 to 120 days, and then after that time, for whatever reasons we don't know yet, that embryo will go ahead and implant and then it will be another 40 to 50 days before a cub would be produced.

WILDTWe have no pregnancy test. We can do an ultrasound of the Giant Panda, but unfortunately, the fetus is so small, you remember the stick of butter, you know, we know it's a very small fetus, that that is not detectable until about the last two weeks of gestation. So Mei Xiang, if she is pregnant, would be having a cub some time from 120 to 170 days from now. So it could be as late as October even.

NNAMDIOnto the telephones. Here is Jason in Parkville, Md. Jason, you're on the air. Go ahead, please.

JASONHi. How are you, Kojo?

NNAMDIGood.

JASONI was just curious. Y'all were talking about the Pandas how they can only reproduce or able to reproduce once a year. Does that have something to do with maybe like the changes of seasons so that's like the prime time for them to reproduce, like that particular time of the year?

NNAMDIDoes it have anything at all to do with climate, Copper Aiken-Palmer and David Wildt?

WILDTWell, in terms of the seasonality, they are definitely seasonal, and what's interesting about Mei Xiang, and what has been a challenge to us over the course of the last few years, of course, is that every year she would come into oestrus, into heat, earlier, so that she was coming in as early as January, and we were sort of perplexed by that because most Giant Pandas will come into heat actually in April or May. And so we were relieved this year for her to actually come in later in the year.

WILDTIn terms of why they only show one oestrus period per year, we're not sure, but it's not related to the seasonality. It's just that seasonality is an inherent part of their reproductive process.

JASONOkay. Well thank y'all.

NNAMDIJason, thank you very much for your call. Cooper Aiken-Palmer, how is Mei Xiang doing today? I assume she's been under intense monitoring this entire time?

AIKEN-PALMERWell, you'll have to come and see her and see how she's doing. But she is up and looking good. She, you know, it's amazing, they'll go back to eating bamboo like nothing ever happened, and they -- the responses I've been getting from the animal care staff that's taking care of her is that she's up, she's eating, and she doesn't realize everything that she's gone through. They are out in the enclosures, she's enjoying this beautiful sunny day that we have here, so why don't you come and see for yourself and see how she's doing?

NNAMDISounds like a great...

AIKEN-PALMERLet me know if you think she looks pregnant.

NNAMDISounds like a great idea. David Wildt, we got an email from Mark who says " It seems like pandas exist at a unique intersection of science and politics. When does China get involved in this story?"

WILDTWell, that's a very interesting question. China is intimately involved in this entire process. After the 2005 birth of Tai Shan, we went through a couple of years with, again, more challenges to natural breeding. We had four years of unsuccessful artificial insemination. So we do have a formal partnership with the Chinese, and so Director Kelly and myself went to China, and we sat down and we talked with our Chinese colleagues, because the pandas are really here to learn about.

WILDTThey're here not just to entertain the public, but we have a major science program, both at the zoo and in China where we are saving habitat, creating more habitat, learning more about the wildlife of China. So we went to China, sat down, and we said we've got some concerns about Mei Xiang and perhaps her fertility. So we developed a collaborative two-year study, with our formal partners in China, and so this is the second year of that study, and so our Chinese colleagues have been coming over every year, and they're sharing their information, and we're sharing our information, and we're really just trying to understand scientifically exactly what's going on here, which does affect the future of our Giant Panda program at the zoo.

NNAMDIAre there members of the Chinese scientific community present if and when a panda is born? Do you expect them to be on hand?

WILDTThey are interested in coming over. They -- we work with them very, very closely. We send folks there, they send folks here. It's part of our long-range agreement, and I'm sure if we end up with some confirmation near the end of the gestation, they will certainly be sending colleagues over. At the same time, I'd just like to say that our team is actually spending a lot of time in China these days. Dr. Aiken-Palmer is getting ready to go over with another colleague to China this summer. We're working on some new projects dealing with infection diseases in Wild Pandas. And so, again, there's this constant interchange between the Chinese colleagues and our own colleagues.

NNAMDICopper Aiken-Palmer, what happens if this attempt does not succeed? Is this the last time you expect you'll be trying to get Mei Xiang pregnant?

AIKEN-PALMERShe's still pretty young. There's quite a bit of time left in her reproductive life. I think the oldest panda to give birth was in her 20s. So I think there's more chance for her. The question is, is the best chance for her here? You know, certainly in China they have more males over there, so maybe she would do better with naturally mating with a different male. Maybe she would do better with artificial insemination from a different male.

AIKEN-PALMERSo I think there's a lot of questions along those lines that may arise, but for now, we're leaving it open to see what happens for her in the future. We recently have developed some projects with Rubenstein fellows to look into some of these questions. You know, we have questions about how often females do give birth and how many offspring they tend to give in their lifetime. So those are all questions that we have as well.

NNAMDICopper Aiken-Palmer is the head veterinarian at the Smithsonian Conservation Biology Institute. She joined us by phone from Front Royal, Va. Dr. Aiken-Palmer, thank you for joining us.

AIKEN-PALMERThank you, Kojo.

NNAMDIDavid Wildt is the senior scientist and head of the Center for Species Survival at the Smithsonian National Zoological Park. David Wildt, thank you for joining us.

WILDTThank you, Kojo. We appreciate everyone's support.

NNAMDIAnd thank you all for listening. I'm Kojo Nnamdi.