Bai Yun is settling into her new living arrangements well. She has always enjoyed being in what is now a behind-the-scenes area, the classroom exhibit, with the nearby bedroom, garden room, and sunroom. Those long-time visitors to the San Diego Zoo may remember this classroom exhibit as one of our original panda exhibits, and Bai Yun has had access to this area on and off since her arrival here in 1996.
The bedroom area is equipped with the birthing den she has chosen for the birth of each of her three cubs. The den is round and comprised of hard plastic with a wooden floor. Currently, she cannot access the den itself, as most of the time it is sealed of with a door closed by the keepers. In this way, staff prevents any other creatures from using the den in the “off season,” even creatures like Su Lin, who lived in this same bedroom just a few days ago.
When Bai Yun shows us some behavioral signs of pregnancy (or pseudopregnancy), we will give her access to her den once again. Once the door is opened, we can expect Bai Yun to familiarize herself with the den again. She will usually sniff around intently at first. Within a few days she will probably scratch heartily at the floors, stand bipedal and scratch the plastic walls, and even stare up into the camera housing that looks down at her from the top of the den. Her initial visits to the den will probably be brief as she acclimates to having this new space allotted to her.
Once her hormone profile really climbs, she will probably begin dragging her bamboo meals into the den, where she will sit and munch in the dark recesses of the small area. It’s the first step in her nest-building process. Keepers will continue to clean the bedrooms and other areas Bai Yun has access to, but they will generally leave the den material alone. After many days of Bai Yun’s activity, the buildup of drying bamboo begins to create quite a big heap on the floor of the den.
Bai Yun will begin sleeping in the den from time to time. Even if she is showing the decreased activity consistent with pregnancy, she usually spends most of her time resting outside the den until she is about a week from giving birth. In the last few days prior to the arrival of a cub, Bai Yun enters the den frequently, rifling through the bamboo on the floor. Occasionally, she picks up an old piece to gnaw on. All of this focus on her dry bamboo stash serves to weave the fragrant fibers into a thick mat that will become her bedding during her postpartum days.
Sometimes we will see her sitting in her den, holding a piece of bamboo culm or a food pan she drags in from her bedroom. She will cradle the object in a manner resembling a dam cradling her infant. She may even fall asleep with the item held in her paws, resting for hours in this maternal pose.
In the weeks leading up to a birth, as her progestin profile elevates dramatically, her appetite will begin to wane. Bears who hibernate do so while fasting and give birth in their dens while in this fasting state. Pandas do not hibernate, but they are still driven by many of the same evolutionary factors that have shaped all bear species. Bai Yun will lose her appetite as she gets closer to a birth and will likely fast for several days postpartum.
For now, Bai Yun is showing none of these acute signs of being close to a birth. Her hormone profile has not yet elevated. However, if she is going to give birth in August, as she has done three times before, we would not expect to see those hormones elevate until the end of this month, at the earliest. Until that time, we are in limbo, a type of “observer diapause,” waiting for the next developments in Bai Yun’s life history.
Suzanne Hall is the senior research laboratory technician for the Giant Panda Conservation Unit of Applied Animal Ecology/CRES.