“Bears are not carnivores in the strictest sense like a cat where they consume a high-protein diet,” said Washington State University’s Professor Charles Robbins.
“In zoos forever, whether it’s polar bears, brown bears or sloth bears, the recommendation has been to feed them as if they are high-protein carnivores. When you do that, you kill them slowly.”
In their experiments, Professor Robbins and colleagues presented captive giant pandas and sloth bears at different U.S. zoos with unlimited food of different types to see their preferences and then recorded the nutritional profiles of their choices.
They conducted feeding trials with a pair of giant pandas to measure their bamboo selection.
They found that the pandas preferred the carbohydrate-rich bamboo culm found in the woody stalks, over the more protein-rich leaves.
At some points, the animals consumed culm almost exclusively — for instance 98% of the time in the month of March.
The researchers also analyzed data from five zoos in China which had giant pandas that had successfully reproduced and found again, a high-carbohydrate, low-protein diet.
In sets of feeding trials, six sloth bears at the Cleveland, Little Rock and San Diego zoos, were presented with unlimited avocados, baked yams, whey and apples.
They chose the fat-rich avocados almost exclusively, eating roughly 88% avocadoes to 12% yams — and ignoring the apples all together.
This showed sloth bears preferred a high-fat, low-carbohydrate diet, which may have a similar makeup to their wild diet of termites and ants as well as their eggs and larvae. It’s also vastly different than the high-carbohydrate diet they are usually fed in captivity.
Sloth bears, which are native to India, typically live only around 17 years in U.S. zoos, almost 20 years less than the maximum lifespan achievable in human care. Their most frequent cause of death is liver cancer.
The researchers saw a similar pattern in previous studies of polar bears that showed captive polar bears, who are normally fed a high-protein diet, would mimic the fat-rich diet of wild polar bears if given the option.
Polar bears in zoos typically die about 10 years earlier than they should, most often of kidney and liver disease. These two diseases can develop from long-term inflammation of those organs, potentially caused by many years of poorly balanced diets.
The current study, along with previous ones, also shows that when captive bears are given dietary options, they will choose foods that imitate the diets of wild bears.
“All of these bears started evolving about 50 million years ago, and in terms of this aspect of their diet, they know more about it than we do. We’re one of the first to be willing to ask the bears: What do you want to eat? What makes you feel well?” Professor Robbins said.
The findings appear in the journal Scientific Reports.
C.T. Robbins et al. 2022. Ursids evolved early and continuously to be low-protein macronutrient omnivores. Sci Rep 12, 15251; doi: 10.1038/s41598-022-19742-z
This article was first published by Sci.News on 3 October 2022. Lead Image: A male giant panda named Xiao Liwu at San Diego Zoo, California, the United States. Image credit: Sci.News.
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