Credit: Tom Gillman
A recent study shows that eating human food has a negative effect on the black bears' gut flora. Researchers from North Carolina State University and Northern Michigan University found that wild bears who ate a lot of processed foods had less diversity in their guts.
"We know a 'western' diet can reduce the number of different types of bugs in the guts of humans, mice and other species, which can have an adverse effect on their health," says the co-author of the study, an assistant professor of applied ecology at NC State. We want to know if the same thing is true for wildlife, given the increasing overlap between where people live and where wildlife lives. If wildlife begin consuming human foods, it may affect their ability to derive as much nutrition from their traditional, wild diet.
Sierra Gillman is the first author of the study and a PhD student at the University of Washington. We wanted to know how human foods affect the gut of black bears. Gillman was a graduate student at NMU.
The study focused on Michigan, which allows hunters to leave out large quantities of human food in order to lure bears. For weeks or months, hunters will bait specific sites to lure bears to the area. Some bears have a diet that is rich in junk food for a long time.
The researchers worked with guides in the Upper Peninsula of Michigan to collect samples from the wild bear population. When the guides went on their regular trips with hunters, they collected samples from bears that had been killed. The guides followed a protocol for retrieving hair and gut samples. The jejunum is the middle section of the small intestine and the colon is the large intestine. The researchers were able to get samples from bears that were legally-harvested.
The researchers used the gut samples to find out how many different types of microbes were present in each bear.
The researchers did an assessment of each bear's long-term diet by analyzing their carbon isotope analysis of their hair. The analysis told researchers the extent to which each bear was consuming sugar and corn, which is more likely to be found in processed foods.
The researchers looked at two measures of gut biodiversity. They look at the total number of different species. They looked at a measure called Faith's phylogenetic diversity, which looks at how many different types of species are present.
Gillman says that Faith's diversity assesses how many branches of the family tree are represented.
The measures of gut biodiversity were lower in bears that had been eating more processed foods.
Black bears that eat more human food have less diversity in their gut microbiomes.
"Sugar is very easy to digest," says McKenney. Lots ofbacteria can eat it. That means that processed human foods have less food available forbacteria that break down fiber or other microaccessible carbohydrates. If bears don't eat enough of their traditional diet, the niche in the food web won't be sustainable. Reducing gut microdiversity is one of the mechanisms we think about.
If the gut of bears suffers when they start consuming more human food, that could make it harder for them to derive as much nutrition from non-human foods. It's not clear how quickly species that break down fiber would return.
Gillman says that they need to do more work to determine what this means for the health of the animals.
"Many hunters use camera traps to monitor their bait sites, and people we've worked with have told us that they see a wide variety of species eating the bear bait."
It's not clear how baiting might affect the health of other wildlife that are taking advantage of the free food. Evaluating the impact of our activities on diversity may need to be done with regard to protecting microbial diversity. The evidence suggests that many of these organisms are critical to the health of wildlife. How does baiting fit in? I think we need to explore those issues.
The Journal of Mammalogy published a paper titled "human-provisioned foods reduce gut microbiome diversity in American black bears".
Sierra J Gillman and her colleagues found that human-provisioned foods reduced gut microbiome diversity in American black bears. There is a DOI of 10.093/jmammal/gyab154.
The Journal of Mammalogy has journal information.
The study found reduced diversity in the guts of wild bears that ate human food.
The document is copyrighted. Any fair dealing for the purpose of private study or research cannot be reproduced without written permission. The content is not intended to be used for anything other than information purposes.
