Are bears really carnivores? A new study led by Washington State University and Texas A&M University adds to a growing body of evidence that bears are not carnivores. Research suggests bears are omnivores like us humans, even though they are fed high-protein diets while in captivity.
“Bears are not carnivores in the strictest sense like a cat, where they consume a high-protein diet,” said Charles Robbins, lead author of the study, which is published in the journal Scientific Reports . “In zoos forever, whether it’s polar bears, grizzly bears or sloth bears, the recommendation has been to feed them like high-protein carnivores. When you do that, you kill them slowly.”
The WSU Bear Center is the only research institution in the United States with a captive population of grizzly bears. Robbins, who founded the center, has studied bear nutrition for decades.
As an example, under human care, sloth bears die up to 20 years earlier than anticipated and data on their nutritional needs is lacking. One theory is that the bears are fed too much protein , which is causing cancer and disease.
“Consumption of diets with inappropriate macronutrient profiles has been associated with increased energy expenditure, poor health, reproductive failure, and premature death . Accordingly, we conducted feeding and preference tests with giant pandas and sloths, a termite and ant feeding specialist,” the researchers wrote.
In their experiments, Robbins and colleagues watched captive giant pandas and sloths 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 gauge their selection of bamboo. They found that the pandas preferred the carbohydrate-rich bamboo stem found in the woody stems, to the more protein-rich leaves.
“We found that giant pandas are low-protein, high-carbohydrate omnivores, while sloth bears are low-protein, high-fat omnivores. The preference for low-protein diets apparently occurred early in ursid evolution and may have been critical to their global spread,” the study authors say.
The researchers also analyzed data from five zoos in China that had successfully bred giant pandas and again found a high-carbohydrate, low-protein diet.
And the polar bears?
The researchers saw a similar pattern in previous studies of polar bears that showed that captive polar bears are normally fed a high-protein diet. Polar bears in zoos often die about 10 years earlier than they should, most often from kidney and liver disease, possibly caused by poorly balanced diets.
“All of these bears started evolving about 50 million years ago, and in terms of this aspect of their diet, they know more than we do. We are one of the first to be willing to ask bears: What do you want to eat? What makes you feel good?” Robbins concluded.
Referencia: Charles T. Robbins, Amelia L. Christian, Travis G. Vineyard, Debbie Thompson, Katrina K. Knott, Troy N. Tollefson, Andrea L. Fidgett, Tryon A. Wickersham. Ursids evolved early and continuously to be low-protein macronutrient omnivores. Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-19742-z