Study Finds Decreased Microbial Diversity in Guts of Wild Bears That Eat Human Food

According to recent research studies, it has been discovered that the consumption of food made for humans, has a considerable effect on the microbiomes of black bears. Much less microbial diversity has been observed in the microbial ecosystem of the digestive tracts of bears that consume factory-processed food. The research study was put together by researchers from Northern Michigan University and North Carolina State University.



The Research

According to Erin McKenney, an assistant professor of applied ecology at NC State and a co-author of the study- “It is known that ‘western diets’ can alter the activities of microbes in the digestive tract of humans and some other more or less domesticated species by reducing their activities”. There was a quest to find out if the same could be said for the wildlife. The reason for this is the rising intersection of the habitations of both wildlife and humans. One of the reasons for the research is the theory that consumption of human nutrition may impact the absorption of nutrients from normal wildlife food if the animal ever returns to its diet.

Read Also: Imbalanced Gut Microbiota: Tips on How to Restore and Maintain a Healthy Intestinal Flora

Sierra Gillman, another researcher and first author of the study as well as a Ph.D. student at the University of Washington, said that to test out the theory, they would have to determine the effects human food has on the microbial activity in the digestive tracts of wild animals. She further added that this particular research study was solely focused on black bears.

The study was mainly conducted in Michigan and is comprised of hunters luring the black bears with huge amounts of human foods. Some examples of foods used in the experiment include sugary cereal and candy. The hunters spent weeks and months setting up bait in certain areas with the intent to attract the black bears to those areas regularly.

For sample collection, the researchers collaborated with certain guides who directed operations with hunters to the upper Peninsula of Michigan. These guides retrieved samples from the bears and this whole process was repeated regularly.

The samples that were specifically collected were hair and digestive tract samples. The digestive tract samples were from both the small and large intestines respectively.

In analyzing the samples gotten from the digestive tract, the research team tried to identify and ascertain the microbial entities present in the microbiome and to acknowledge the quantity of each microbial organism found in the digestive tract.

Read Also: Swiss Study Finds Link Between Multiple Sclerosis and the Intestinal Flora

In the process of analyzing the bear hair sample, the carbon isotope technique was utilized and this method was used to specify the long-term diet of the bears.

In the data collection process, two principal parameters were used to measure the biodiversity of the digestive tracts: the number of different species present and Faith’s phylogenetic diversity- (an assay of the categories of species present).

This according to Gillman, is a method of determining the degree of diversity of the bacterial family trees that can be accounted for.

The eventual outcome of the research is that ingestion of human nutrition decreases the amount and biodiversity of microbes in the digestive tract.

The reduction in the diversity of microbes is the reason why bears find it difficult to absorb as much nutrient if they eventually return to their usual wild diet.

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Clinical Significance

The clinical significance of the study is the discovery that consumption of human nutrition brings about a substantial decline in the amount of microbial biodiversity in the digestive tract of wild animals. In the event of these wild animals returning to their normal wild diet, the studies show that they might find it difficult to digest and absorb some of the foods they previously had no problem digesting. Could our hyper-processed diets be doing something similar to our intestines?


Altering wildlife diets to allow them to consume human food is shown to be associated with an alteration of microbiota in the digestive tract of these wild animals. An altered microbiota could pose some future problems if the wild animals eventually return to their wild diet.

Read Also: Pregnancy: The Importance of Maternal Intestinal Flora to the Development of the Immune System of the Fetus


Human-provisioned foods reduce gut microbiome diversity in American black bears (Ursus americanus)



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