Weaning Panda Cubs

Before anyone reads the title of this blog post and panics: No, we are not ready to facilitate the weaning of Yun Zi from his mother!

Our littlest panda is just over a year of age. When he is closer to the traditional age of 18 months, we will aid Bai Yun in weaning her offspring, but I have seen in the comments of recent postings that there have been several questions about the separation process. Here I will attempt to respond to some of those inquiries.

Is Bai Yun weaning Yun Zi earlier than her other cubs?
This is an extremely difficult question to answer. The fact is, we don’t know with certainty how wild pandas wean their offspring. Is it a slow, gradual increase in separation time that culminates in a mother bear deciding not to reunite with her cub? Is it an abrupt end to an otherwise pleasant social pairing? Researchers have noted with other bear species that cubs have been driven off by males in order to mate with the mother. Another option is that mothers drive their cubs away on their own. Either way, parent-offspring conflict is a force in separating mother from offspring. In truth, wild panda weaning has not been documented. We do know that young pandas begin experiencing long absences by their mother at an early age. Bai Yun has certainly taken the opportunity to spend hours on end distant from Yun Zi, in the same way she has done with previous cubs.

Does Bai Yun refuse to nurse Yun Zi, and is this evidence of weaning?
In short: yes. Yun Zi does not nurse as frequently as he did when very young. This is a natural mammalian progression that changes due to the increasing capacity of the offspring’s stomach. However, at a year of age, Yun Zi has probably developed the teeth necessary to feed on bamboo (there hasn’t been a recent cub exam to say for sure), which means he can begin ingesting some of his routine calories from the plant that will become his staple. This is the beginning of the end of maternal dependence for Yun Zi. As he takes in more bamboo, his need for mother’s milk will diminish. Mind you, I said his need will diminish, but his desire for milk will not easily abate: hence, parent-offspring conflict. Human or bear, offspring typically want more of their mother than mother is willing to give.

What behaviors suggest Bai Yun is ready for weaning to occur?
Parent-offspring conflict takes many forms. In the past, Bai Yun will refuse nursing, or terminate bouts of nursing more frequently. She may become more aggressive about guarding her bamboo stash as she feeds or become rougher during play with her cub. But she will be prevented from putting real distance between herself and Yun Zi because she lives in a facility with barriers to her natural tendency to move about. Unlike her wild counterparts, she cannot simply walk away. This is why we must step in and facilitate weaning at the appropriate time.

For the mother panda, rearing of young is a balancing act. The female must weigh the costs and benefits of investing in her offspring. The benefits seem obvious to us: a healthy panda cub that grows and reproduces, passing on that mother’s genes to the next generation. The costs may be more subtle in our zoo setting, but they are still very real to Bai Yun: the energy required to gestate, birth, lactate, and rear offspring takes an enormous toll on the female body. At some point, the female needs to break free from the energetic demands of her youngster and reallocate her resources to ensure her own survival. Without doing so, she may not achieve her optimal reproductive fitness; that is to say, she may not succeed at having as many viable offspring—capable of having their own cubs—as she might otherwise. Protecting her own health and well-being is an investment in a mother’s future progeny.

As you watch the interplay between Bai Yun and Yun Zi over the coming months, keep in mind the conflict that is developing below the surface. Understand that there is no natural resolution to that conflict in a zoo setting without our involvement. If we don’t open and close a few doors, Bai Yun will be unable to fully reallocate her resources to her own personal well-being. And we all know the adage, “If Momma ain’t happy…”

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, SKRs Get TLC.

Watch video of our panda hearing study!

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