Did Giant Panda in the zoo really need that amount of food every day?

   

     I'm still recovering from last week's hectic schedule, and this week promises to be even busier. When I was building a castle in the air, a thought jumped out of nowhere, " Can I be like a Panda in the zoo? Alternate between eating and sleeping." And here comes the question, why did giant panda need that amount of bamboo every day?

    In the blog post last time, we mentioned that giant pandas actually spent 16 hours a day eating, and the gene mutation has changed the habits of the giant pandas. But as a science student, I crave to know more about it. How much weight of food did a giant panda consume in a day? Where has that energy gone?

    Therefore, I did a series of research and data collecting to verify my assumption.

Data collection and research

    First, I found the daily routine of a giant panda in a zoo and the weight of food a giant panda consumes in a day. According to the Smithsonian's National Zoo and Conservation Biology Institute,  at 7 a.m., 15 pounds of breakfast was prepared for each giant panda. At 9 a.m., the zoo is open to visitors, fresh bamboo, enrichments and puzzles were prepared for the giant panda, this can be said to keep the giant panda waking up while visitors are around. Around 10 a.m., it was the giant panda's late morning nap. 11a.m., it's their mid-morning snack time, and at 1:30 p.m., they will have their lunch. After that, the keeper will just weigh and prepare overnight food for them. The rest of the time, those pandas were just taking a nap and playing for an hour in the evening. In conclusion, an adult giant panda consumes 70 to 100 pounds of bamboo each day. 

    Since giant panda spends most of the day eating and sleeping, sleeping will be the only energy-consuming activity. Hence, a study by Dr Nie showed that the average daily energy expenditure (DEE) across five captivate and three wild pandas is 5.2 megajoules/day, and the mean for wild pandas is 6.2 megajoules/day. It's only 38 percent of the average of a terrestrial mammal of the same body mass. Besides, giant panda has thick fur which traps the body heat they have inside, this means they don't have to consume energy to regulate their body temperature, and their metabolism rate is low. Furthermore, research revealed that giant panda has smaller kidney, liver and brain when compared to other bears and its thyroid hormone levels are as low as a hibernating black bear's hormone levels. Lastly, researchers found a panda-specific mutation on the DUOX2 gene, the deletion of which is connected with underactive thyroids in humans.

    Despite gene mutation and habits, giant pandas actually can't really digest bamboo. According to research by Dr Pang, 17 percent of bamboo leaves and stems can be digested, and most of the faeces are composed of undigested bamboo fragments. Moreover, plant-degrading bacteria such as Ruminococcaceae and Bacteroides, which are normally concentrated in other herbivores, were not found in the giant panda gut, but were predominated by Escherichia/Shigella and Streptococcus.    

 Conclusion

      Taken together, panda bears' low energy expenditures, thyroid hormone levels and formation of panda gut enable giant panda to munch on bamboo all day.

References

Nicole MacCorkle, 2019, A Day in the Life of a Giant Panda Keeper,  Smithsonian's National Zoo and Conservation Biology Institute, viewed 31 October 2023, <A Day in the Life of a Giant Panda Keeper | Smithsonian's National Zoo (si.edu)>

Yonggang Nie et al. 2015. 'Exceptionally low daily energy expenditure in the bamboo-eating giant panda'. Science, vol. 349, no. 6244, pp. 171-174; doi: 10.1126/science.aab2413

American Society of Microbiology, 2015, Giant panda gut bacteria can't efficiently digest bamboo, PHYS.ORG, viewed 31 October 2023, <Giant panda gut bacteria can't efficiently digest bamboo (phys.org)>