Following a final ultrasound and hormone analysis, Zoo staff confirmed late yesterday that Mei Xiang is not pregnant but was experiencing a pseudo, or false, pregnancy during the past several months.
Zoo scientists, veterinarians, keepers, and FONZ volunteers were keeping a close eye on Mei, monitoring her hormone levels and behavior, as well as conducting weekly ultrasound exams in an attempt to determine if she was pregnant. On April 23, Mei’s progestagen concentrations had declined sufficiently to start the 24-hour watch. On reaching normal baseline levels, this decline ends in either the birth of a cub or the end of a pseudopregnancy. Based on current hormone analyses, and not having seen a fetus during the ultrasound exams, Zoo researchers have determined that Mei Xiang experienced a pseudopregnancy.
Female giant pandas almost always undergo a pseudopregnancy when they ovulate but fail to conceive. During a pseudopregnancy, hormonal changes and behaviors are identical to those of a true pregnancy, making it very difficult to determine if a giant panda is actually pregnant or not. This is the fifth time Mei Xiang has had a pseudopregnancy.
We expect Mei to return to normal, hormonally and behaviorally, in the coming days, which includes an increase in appetite and activity level.
Mei Xiang continues to exhibit maternal behaviors such as cradling the Kong toy, rearranging the “nest,” and some body licking. These behaviors are slowly diminishing. Mei readily participated in ultrasound exams both yesterday and today, although she was reluctant to leave her den both days. She continues to have a great appetite frequently pulling bamboo inside to dine in the close quarters of her den.
Mei Xiang started ano-genital licking for the first time for five minutes during the 10 a.m.-1 p.m. shift yesterday. This behavior usually starts when her progestagens reach baseline and it is the behavioral signal that the end is here. Ano-genital licking was also observed during each of the shifts from 1 p.m. to 4 a.m. None of these bouts match the extended ano-genital licking that is seen prior to a birth.
Over the past 24 hours, Mei Xiang remained mostly in her nest cradling her “Kong baby” as if it were a cub. There were brief episodes of paw licking and nipple licking over the past 24 hours. This morning Mei Xiang was alert and eating in her exhibit enclosures, although a bit anxious to return to her den when shifted for cleaning and placing bamboo. In her nest is an array of Kong, spool, and ball “babies,” but sadly no cub.
Mei Xiang is continuing to spend most of her time in the den. Only one brief bout of nest building was observed between 7 and 10 p.m. last night. Mei is displaying some maternal behaviors, but not more than about two minutes per three-hour shift. Maternal behaviors from yesterday through 10 a.m. this morning consisted of mostly paw and nipple licking. Mei was observed briefly cradling a ball three times for a few seconds at a time. During the 7-10 a.m. behavior watch shift this morning, she was out in her enclosures and was observed scent-marking.
Mei Xiang continues to be bright and alert and is consuming her bamboo voraciously. She drags bamboo into her den and then begins to eat it. She is still nest building—shredding bamboo and sometimes rearranging it, as it falls around her.
This morning for the first time, she remained in the den after the keepers arrived until 9 a.m. We have observed two brief bouts of anogenital licking lasting about one and a half minutes each. After one bout of a-g licking she following with about a half-minute bout of nipple licking. This increase in body grooming is an indication that her hormones may be closer to baseline. Our 24-hour behavior watch starts today. Whether a cub is on the way is anyone’s guess!
Mei Xiang continues to keep us guessing. She has a great appetite and continues to strip and eat the culm, or inner stalk, of all the bamboo offered to her. She is wide awake and cooperative with her keepers, often watching through the window as they place her next meal.
Mei also continues to cooperate with ultrasound procedures, lying calmly on her back for the exam and then intensely playing with her “gelly” belly afterwards. The ultrasound gel makes her double over and rub her belly and ears vigorously, exhaling with pleasure. Rolling on her back reminds one staff member of a breakdancing back spin as she scent anoints her body with the gel.
In the wild, pandas nest in tree holes, caves, and crevices, as well as under mountain side ledges. Since cubs must be held by their mothers for proper thermoregulation and easy access to milk, rearing is a 24/7 affair. Little effort is put into building an elaborate nest. Over the past week Mei Xiang has been consistently shredding bamboo culm in the den, in addition to everywhere else in her enclosures. She has a variety of toys and even her “Kong baby”, a rubber cub-sized dog toy that she will frequently cradle at this stage of a pregnancy or pseudopregnancy. She has carried the toys (a ball and a spool) into the den but removes the “Kong baby” when the keepers move it into her den. Although her behavior is not providing consistent cues, her hormones are indicating a familiar pattern that indicates we are reaching the end of this pregnancy event.
Mei Xiang is just beginning to take a recess from her normal activities in correlation with her elevated progestagen levels. This compound is a metabolite or a specific component of progesterone, the hormone responsible for the physiological and behavioral changes associated with sustaining pregnancy. Daily urine samples provide us with a hormonal window into what might be transpiring inside her body.
In addition to hormone levels we are also closely watching changes in her behavior. Since this past Monday, Mei has decided after her morning training sessions to decline to go outdoors and instead return to her indoor enclosures. Although the den is available, she is not yet on retreat there. Completely relaxed and sated, Mei Xiang spends the next several hours lounging on the rock work, in air-conditioned comfort. Mei has over the past three weeks been slowly decreasing her bamboo consumption, but over the past two days instead of immediately consuming her produce (apple, carrot, and sweet potato), she has started to leave pieces behind. Today she left a perfectly cored apple after one of her now more delicate and selective feedings.
Mei has also started to groom her paws. Some of the grooming may be due to the juices of the delicious pear half, which she especially savors after her training session. However, she continued to lick and groom her paws today. This extended grooming is touchingly similar to the attention and care given to a cub. We are seeing just the beginning of grooming behavior associated with pregnancy. Female pandas may dramatically increase their body grooming during the last week of pregnancy, with a more focused attention on the ano-genital region. This behavior is a helpful indicator of an impending birth, or the end of a pseudopregnancy.
Zoo scientists detected a secondary rise in Mei Xiang's urinary progestagen levels on March 30. This hormone rise indicates that it should be 40 to 50 days before she either gives birth to a cub or comes to the end of a pseudopregnancy, or false pregnancy, which is common in giant pandas.
Similar to last year’s unusually early estrus, Mei Xiang once again came into heat at the beginning of January, with Zoo scientists artificially inseminating her with Tian Tian's semen on January 9 and 10. There is no conclusive study that indicates what causes panda ovulation, although scientists know that giant pandas mostly breed in late winter to early spring.
Since the artificial insemination, scientists have conducted weekly hormonal analyses on urine samples from Mei Xiang. Our veterinarians are also conducting weekly ultrasounds on her to monitor any changes in her reproductive tract and look for evidence of a fetus. So far, they have not seen an indication of one. Because panda fetuses do not start developing until the last weeks of a gestation period, the veterinarians say they do not yet expect to see a fetus. They stress that it is still too early to determine if Mei Xiang is pregnant or experiencing a pseudopregnancy. In 2005, in the last weeks leading up to the birth of Mei’s only cub. Tai Shan, she would not cooperate for her weekly ultrasounds, and it was not possible to definitively determine if she was pregnant.
The longer days of early spring cast long shadows on the floor of panda enclosure number four, now empty since Tai Shan’s departure in February. We feel the emptiness and at the same time, we are buoyed by the warm sunlight we so welcome after our seemingly endless winter. Tai Shan has settled with confidence into new surroundings, devoured new bamboo species, and enjoys the attentive care of his expert panda keepers, on the other side of the world. Food is the universal language, which eases all transitions, and Tai has handled it all exceptionally, as documented in the photos of double-fisted feasts, on homemade panda bread.
Mei Xiang and Tian Tian continue about their daily routine. As we provide and monitor enrichment, perhaps we can persuade them to better favor the mysterious enclosure number four. For now, it remains unoccupied. Mei Xiang is being closely monitored for signs of a real pregnancy. Only slight changes have started to be observed. Mei is eating less bamboo, could it be...? Or is it the warmer weather? Ah, she is a bit spacey and slow moving today, perhaps she will go to her den... and then she goes outside! Yes, we all know the 50-50 nature of our endeavors, the possibility of another pseudo, or false, pregnancy, however we hope with every passing day that this year will be a golden one and that we will experience the joys of 2005 all over again.
Even though we do not know definitively what will happen, we prepare for all possibilities. The volunteers get data-collection training. The cameras are serviced to ensure they're in working order. Mei Xiang is trained in her den and monitored by ultrasound. All maintenance repairs are completed. Nursery inventory is reviewed in case a cub needs special care. Formula-making is practiced. Building closing plans are developed to ensure Mei has a quiet den environment. Management protocols for birth are reviewed, in case of a single cub or twins. And last but not least, Tian Tian, who is still in rut, needs extra feedings and enrichment, to ensure his well being.
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