Mei Xiang has started exhibiting more behaviors consistent with the secondary hormone phase of a pregnancy or a pseudopregnancy. That means that she has been spending the majority of her time sleeping. Simultaneously, she is starting to build a nest in her den and to eat less. Keepers have also seen the first signs of self-grooming from her. All of these behaviors are expected and normal for a female in the secondary hormone phase.

During the later stages of a pregnancy or pseudopregnancy, a very sleepy Mei Xiang will settle and sleep for much longer periods, and if she is pregnant the panda team wants her to give birth inside where they can quickly provide help if necessary. Although she is spending all of her time inside her air-conditioned enclosures, Mei Xiang will make it very clear if she does want to go outside, and keepers are monitoring her via the panda cams to see if her behavior changes. Meanwhile, veterinarians are continuing to track changes in her uterus with weekly ultrasounds, but it is likely still too early to see a fetus if Mei Xiang is pregnant. The only way to definitively determine if a female is pregnant is to see a fetus on an ultrasound. Their behavior and hormones mimic a pregnancy even if they are experiencing a pseudopregnancy.

Unlike in humans, the implantation of a fertilized egg for a panda can occur months after ovulation. It’s a phenomenon referred to as embryonic diapause or delayed implantation. Here, the eggs start to divide and then fetal development stops. At this point, the embryo floats around in the uterus until, at a later stage, it attaches to the uterine wall and gestational development continues. Some embryos implant shortly after fertilization and pandas give birth in as little as three months; other times it can even take six months to see signs of a viable pregnancy. With the implantation comes a surge in progesterone—which scientists refer to as a secondary hormone rise. 

It’s still too early to tell if Mei Xiang is pregnant or experiencing a pseudopregnancy, but the panda team will continue to monitor her behavior, hormones and changes in her uterus.

Tian Tian's 20th Birthday

Tian Tian is turning 20 years old Aug. 27, and he will also celebrate with a frozen cake at 9 a.m. in his yard. 

Bei Bei's Second Birthday 

Bei Bei turned two years old Aug. 22! He celebrated with a panda-friendly frozen cake made by the Zoo's department of nutrition and birthday-themed enrichment.