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panda cub weaning

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Weaning Xiao Liwu: Conflict over Calories

Xiao Liwu nibbles on a bamboo stalk.

Xiao Liwu nibbles on a bamboo stalk.

Over the last week or so, we have allowed our giant panda mother-cub pair access to more space to see what kind of behavioral pattern develops. We’ve watched Bai Yun and Xiao Liwu closely during this time, both with formalized behavioral observations and informal sessions by keepers and staff. What we have seen is rather typical for this stage in their lives together. Bai Yun is food-focused, moving around both exhibits in search of the choicest bamboo and other snacks. Xiao Liwu is also becoming increasingly food-focused, though interested only in bamboo. When he is finished eating, he follows his mother around, like a little shadow.

Interestingly, this cub is not ingesting much kibble or produce. This makes him rather unique among his siblings in that they were motivated to feed on these calorie-dense items. Xiao Liwu, on the other hand, is limiting all of his non-milk calories to bamboo, which makes it that much more important that he gets plenty of his leafy greens. Since he is nursing very infrequently, probably less than once each day, his bamboo intake is meeting most of his energetic needs.

This is where a conflict arises. Bai Yun is quite determined to meet her caloric needs as well, and though she ingests a lot of produce and kibble, she’s also keen to exploit the bamboo resources we provide. Right now, she has a little competition for the choicest bits, and we have witnessed several bouts of wrestling over bamboo between mother and cub as a result. She’ll even steal the cub’s bamboo and hold him at bay, squealing, while she munches on the remnants of what Wu was working on. Though we provide the two bears with plenty of food, sometimes Wu loses out to his mother with respect to the bamboo he wants. Although he can usually walk away and find something else to snack on, we wonder to what degree his ability to meet his caloric needs is inhibited by his mother.

When not feeding, Xiao Liwu moves about the exhibits in fairly close proximity to his mother. Bai Yun, on the other hand, has not been observed following her son. This is a pattern we have observed with past panda cubs. If the little ones had their way, weaning separations would be delayed by months, or even years! Who wants to give up on the milk bar and the built-in playmate? But Bai Yun is less interested in fulfilling these roles as time goes by. Rejection of nursing bouts is something we have seen off and on for some time. And play bouts are not always welcome. For example, we recently witnessed a bout in which Wu bounded onto his mother with a sudden leap, resulting in Bai Yun biting down hard enough on him to elicit a loud yelp. This brought the play bout to a skidding halt, which may have been the result Bai Yun was going for. As this kind of interaction becomes more common, it reinforces for us the importance of considering momma bear in the weaning equation.

The indicators suggest to us that we should move ahead with our weaning protocol. For this reason, you will notice that Bai Yun and Xiao Liwu will now have periods of separation, each one housed in one of the main exhibits for a few hours each day. The bears will be separated in the morning and given their own foods to chow down on. The cub will not have to worry about his mother stealing his breakfast, and Bai Yun won’t have to worry about play bouts interrupting her meal. We’ll bring them back together about lunchtime and repeat the process the following day. We will, as usual, be watching closely to see how the bears adapt. Stay tuned to this channel for further updates as the process unfolds.

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, Weaning Xiao Liwu.

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The Next Stage

Zhen Zhen

While watching Zhen Zhen and Bai Yun, it shows that we’re getting close to a new stage for the panda youngster. In just a few months we will see Zhen Zhen and Bai Yun begin to separate. This would normally happen in the wild anywhere from 18 months to 2 years old. Although Zhen Zhen does still nurse from mom, Bai Yun will ween the cub completely soon. Zhen is actually eating a very good amount of bamboo already. She has shown a lot of interest in the stalk of the bamboo, and has shown all of us that she can maneuver the bamboo to eat the same thick part as mom. Panda cubs first begin eating solids around 10 months, usually starting on the leaves and smaller parts of the stalk. As they grow older, they will be able to break through bamboo quickly, and efficiently.

Zhen Zhen has been spending a good amount of time on her own and entertaining everyone at the San Diego Zoo’s Giant Panda Research Station. As we get closer to the 18-month mark, keepers and researchers will observe Bai Yun’s behavior toward the cub and will decide when it would be a good time to begin the separation process. Bai Yun may be a little unwilling to share food, and sometimes even space. At 18  months, the cub will become a solitary giant panda just like she would in the wild.

Here at the Zoo, we are hoping to preserve the natural behavior of the animals, and with the giant pandas this has paid off. Having Bai Yun be such an experienced mom helps us with this process as well. She knows exactly what will be going on with the cub and prepares the cub for her life without mom. Zhen Zhen will have her own enclosure here at the Zoo and will still be able to be viewed by the public.

Leaving mom at 18 months also allows Bai Yun time to herself before she comes into her next estrus. Female giant pandas will only come into estrus once a year, but if the female is caring for a cub still in the den she will skip that estrus. The separation at 18 months will make sure that she is still able to cycle.

Anastasia Horning is a panda narrator at the San Diego Zoo.