Zoo scientists have detected a secondary rise in urinary progestin levels in Mei Xiang. The results from yesterday's test lead them to believe the hormone rise indicates that it would be mid- to late July before Mei Xiang either gives birth to a cub or comes to the end of a pseudopregnancy, or false pregnancy, which is common in giant pandas.
Our scientists artificially inseminated Mei Xiang with semen from Tian Tian March 19. Since then, the scientists have conducted weekly hormonal analyses on urine samples from Mei Xiang. Zoo veterinarians are conducting weekly ultrasounds on Mei Xiang to monitor any changes in her reproductive tract and look for evidence of a fetus. So far, they have not seen evidence of one. Because panda fetuses do not start developing until the last weeks of a gestation period, Zoo veterinarians say they do not yet expect to see a fetus. They stress that it is still too early to determine if Mei is actually pregnant or experiencing a pseudopregnancy. Stay tuned!
It is the time of year when bamboo begins to lose its allure and increasing numbers of stalks are left uneaten with each passing day. The pandas have been spending more time resting in their grottos away from the heat, on these early summer days. Mei Xiang’s first priority is to retreat to the air-conditioned indoor enclosures as soon as possible, after the morning cleaning, for a long nap. Other than some occasional bamboo shreds, we can tell she is spending more time in the dens overnight, from the number of droppings left behind.
Tai Shan weighs in at about 181 pounds. Both Tai Shan and Tian Tian are also beginning to spend more hours resting and less time eating. Tai and Tian still have their restless moments, roaming their enclosures. Yesterday for enrichment they had burlap bags and bed sheets stuffed with hay and leaf-eater biscuits. Tai wondered what monster had landed in his yard at first, but after several approaches, and lots of sniffing, he settled into a long rip and search for the biscuits, hidden within.
Switching their enclosures regularly provides sensory stimulation through interactions with each other's scent marks. Scent-mark investigation tells pandas who their neighbors are, and who is passing through their home ranges, out in the wild. It also keeps us all on our toes trying to identify who is who while watching the panda cam. Tai Shan has eye patches that flair out at the outer lower corner. Tai also has two very distinct marks at the bridge of his nose, sometimes looking like a V from a distance. It is a good thing that Tian Tian’s nose dots have faded, lessening the confusion... maybe just a little.
Mei Xiang has started to shred bamboo in Den Three. This activity is called “nest building” even though it only involves carrying a piece of bamboo to the den, shredding up part of the culm or stalk, and then sitting on it wherever it lands. As far as other behavior possibly related to pregnancy, Mei has left her carrots uneaten on a few occasions. For some reason known only to Mei, when her progesterone levels rise during pregnancy (or pseudopregnancy), carrots lose their appeal. Also, Mei has been choosing to rest indoors more frequently, often settling in for a long nap, when our plan was for her to shift back outside for bamboo.
Tai Shan last weighed in at 181 pounds on April 30. Tai is also into rearranging his bamboo. He will pick it up and carry it around the yard and sometimes even up in the trees. Perhaps a different hormone, testosterone, is behind his wanderings. We have a small study in progress to analyze hormones in fecal samples to learn about the earliest onset of maturation in our juvenile male panda. Just like the adults, Tai continues to eat up to about 40 pounds of bamboo culm each day. Yellow fibrous droppings are everywhere around the enclosures. Since they digest only 12 to 23 percent of what they eat, all three pandas have the keepers busy with both ends, going and coming!
Tian Tian gets the restless panda award. We continue to rotate yards and give him access to multiple yards to burn off energy. We give him several enrichment activities each day to help keep him occupied. He is an enrichment challenge. Tian still bleats endearingly for his keepers, and relishes our attention. These are cherished moments for the panda and his keepers.
As we reported last week, Mei Xiang ovulated on March 19. She has continued to show estrous behavior, bleating at her keepers and walking backwards with her tail up when she sees Tian Tian through the window that sits between their yards. Tian’s internal scent analysis tells him that her estrogen has waned and she deserves barely a glance. However, he still chooses frequently to rest near her on the other side of the fence line. We will continue to do daily vaginal swabs until her cells return to their normal everyday composition. Externally, her genitals look almost normal again, only the faintest blush of pink remains and the swelling is just about gone. One has to wonder, if in the wild, very young male pandas would gain valuable experience interacting with females in estrus that have been abandoned by bigger and wiser males.
This morning the David M. Rubenstein Family Giant Panda Habitat is much, much more peaceful than the past two mornings. We collected morning urine samples and swabs for cells to look at Mei Xiang’s vaginal cytology. During the collection we noted that her genital swelling had decreased and the pink coloring had faded. The latest hormonal analysis confirms that Mei Xiang ovulated yesterday. Mei is still showing estrus behavior. She is presenting and raising her tail to Tian Tian, who is moaning and growling at her through the mesh barriers. When he vocalizes in this way, we know that the breeding season is definitely over.
The pandas went right outside when given access. They have fully recovered from their procedures and are making up for having eaten less over the past two days. During the ovulatory period, pandas lose their appetites. We also have to eliminate food and water in preparation for possible anesthesia for artificial insemination (AI). Yesterday, at about 2 p.m., a single trans-cervical AI procedure was performed with fresh semen collected from Tian Tian. The procedure went smoothly. Only 1.7 milliliters was inserted but it contained millions of sperm! We all hope that just one will get the job done. And so the long wait begins.
The 2008 giant panda mating season began yesterday. Mei Xiang and Tian Tian attempted to mate throughout the day. Zoo staff carefully observed each mating and, because satisfactory mating did not occur, Zoo scientists and veterinarians performed a nonsurgical artificial insemination this morning. Both pandas were anesthetized, allowing Zoo scientists to collect sperm from Tian Tian and insert it directly into Mei Xiang’s uterus.
Mei and Tian will remain separated for the next few months, until Mei either delivers a cub, or until Zoo scientists determine that she is not pregnant. Keeping the pandas separated will reduce the risk of increased stress hormone levels in Mei, which could jeopardize ovulation, conception and implantation. Veterinarians will monitor her hormone levels and perform ultrasounds to determine whether or not she is pregnant. We will be sure to keep all of you up to date.
This year’s breeding is very similar to what took place in 2005, when scientists performed an artificial insemination after natural mating attempts between the two bears proved unsuccessful. That led to Tai Shan!
Over the past four days the pandas' behavior has been fairly consistent. Tian Tian is pacing, power walking, and pirouetting around his yard and checking the mesh windows for an opportunity to check on Mei Xiang. When Mei is nearby, she alternates chirping provocatively, with her higher pitched “stay away from me” squeal. Tian watches intently with his ears forward, sitting on his haunches with his face pressed against the mesh. As soon as she scolds, he usually gives up and walks away, returning to his bamboo, if only for a short time before going back and checking again. Mei Xiang is also pacing. She is spending more time on the ground and less time climbing in the trees, since she does not need to avoid or deter any advances from Tian.
We shift her indoors in the afternoon for urine collection. She has filled her afternoons with long naps on the rocks. She is declining to eat most of her bamboo. When given a fruitsicle, instead of consuming it with her usual pleasure, she used it to anoint her entire body and once the remains melted, she rolled in it. What a sticky mess! Thankfully, she still enjoys her produce, which enables us to collect swabs for vaginal cytology each morning.
Mei is also bleating at her keepers. She seems to be withholding this vocalization when Tian Tian is near. This is the only time of year we hear Mei bleat. It should be only a couple more days. Check out the 2008 Pregnancy Watch for updates on Mei's reproductive state.
It is our great hope that Mei Xiang will produce a cub this year to contribute to the world’s giant panda population in zoos and breeding centers. A team of experts here at the Zoo has developed a comprehensive breeding plan, taking into consideration the genetic goals for the zoo population as well as the welfare of each panda.
In 2007, the National Zoo collaborated with the San Diego Zoo to use frozen semen from San Diego's male panda Gao Gao to artificially inseminate Mei Xiang. In this year's breeding plan, he was again considered to be a genetically ideal sperm donor for Mei. In February, however, Gao Gao exhibited signs of discomfort and was examined. A definitive cause could not be found but the symptoms could be related to arthritis. Because his condition is still being monitored, the decision was made not to anesthetize him for semen collection.
Because female pandas ovulate only once a year and are fertile for only about 48 hours, the Zoo will proceed with plans to mate Mei Xiang with Tian Tian. Ideally, they will mate naturally but the Zoo's team of reproduction scientists is also preparing for an artificial insemination. Three years ago, the pandas were given the chance to naturally mate but when their encounters did not appear successful, scientists conducted an artificial insemination, which happily resulted in Tai Shan!
Mei Xiang has just begun to exhibit estrous behavior, including pacing and scent marking. We began conducting weekly vaginal swabs and ultrasound examinations on January 9. Vaginal swabs are now examined daily for cellular changes, which will help pinpoint ovulation. Urine samples are also collected daily to track her hormone profile.
Mei and Tian will continue to be housed separately until the time we anticipate ovulation will occur. During the ovulatory period, they will be housed together with the goal of natural mating. They may be housed indoors or outdoors during this period. They will be separated again following breeding (or artificial insemination) and remain apart afterwards. Their social interactions will be limited to contact through mesh until the birth of a cub or the confirmation of the end of a pseudopregnancy. (Female giant pandas almost always undergo a pseudopregnancy when they ovulate but fail to conceive.) This decision was made to reduce the risk of increasing stress hormones, which could jeopardize ovulation, conception, and implantation.
Tai Shan is very interested in the vocalizations and activities of the adults. The animal-care staff are making a special attempt to give him opportunities to observe the adults’ interactions. Young pandas in the wild may be present on the periphery of adult interactions and watching them may benefit their behavioral development. At this time of year, pandas eat a large quantity of bamboo culm or stem. When Tai is not focused on the activities next door, he is busy eating. He currently weighs 170 pounds.
FONZ volunteer web-cam operators are on duty from 7 a.m. to 7 p.m. During the ovulatory period, volunteers will assist in monitoring the pandas during extended overnight shifts. Please be aware that the indoor part of the David M. Rubenstein Family Giant Panda Habitat may be closed throughout this period with little or no notice. We appreciate your patience and support.