The panda team has started seeing more pronounced behavioral changes in Mei Xiang, which is normal and expected for a pregnant or pseudopregnant giant panda. Overall, she is spending more time sleeping and is less responsive to the keepers.
Mei Xiang is usually anxiously waiting at the door to venture outside for her bamboo breakfast when the keepers arrive in the morning, but lately she has been sleeping in, only rousing after the keepers have filled her yard with bamboo. That bamboo breakfast is increasingly becoming the only part of the day she chooses to spend outside. She is also eating less bamboo, which is normal for a panda in the final stages of a pregnancy or pseudopregnancy. However, she is still eating some of her favorite things like apples, pears and biscuits. She is also steadily building a nest in her den and the soft cushion of shredded bamboo now mostly covers the floor.
At some point in the next several weeks, Mei Xiang will likely choose to stay inside all day and spend almost all of her time sleeping. She also may start spending extended periods of time in her den. In the past she has moved some of her toys and feeders in the den to cradle like she would a newborn cub. She also will become much more sensitive to noise.
The changes in her behavior correlate with the hormonal changes endocrinologists at the Smithsonian Conservation Biology Institute have been tracking. Her urinary levels of progesterone are rising, which indicates that she is in her secondary hormone rise. This secondary rise indicates that Mei Xiang will either give birth or experience the final stages of a pseudopregnancy within the next month. Scientists cannot determine if a giant panda is pregnant from behavior and hormonal analysis alone because her behavior and hormones will mimic a pregnancy even if she is not pregnant.
The only definitive way to determine if Mei Xiang is pregnant before she gives birth is to detect a fetus on an ultrasound. Veterinarians have are conducting ultrasounds twice a week to track changes in Mei Xiang’s reproductive tract, but they have not seen anything yet. It is important that Mei Xiang is comfortable with the procedure and is trained to participate in it because she is more reactive to change and unfamiliar things at the end of a pregnancy or pseudopregnancy. If she is trained to participate in and is comfortable with having an ultrasound, it increases the chances she will participate in the final stages of a pregnancy or pseudopregnancy. However, she always has the choice to participate. If she chooses not to participate, she can leave the training chute at any time and veterinarians will not perform an ultrasound.
Giant pandas experience delayed implantation, meaning that an embryo floats in the uterus after fertilization and does not implant in the uterine wall until a few weeks before birth. It grows exponentially after it implants, but scientists do not understand what causes an embryo to finally implant in the uterine wall.
In the next several weeks, as we near the time when Mei Xiang will either give birth or the end of a pseudopregnancy, the panda cams will focus on her instead of rotating between her, Tian Tian and Bei Bei. Specially trained behavior watchers with Friends of the National Zoo will monitor her behavior 24 hours-a-day and look for signs of an impending birth.