Habitat and diet shape the guts of Alaskan brown bears

A new study led by Northern Michigan University (NMU) has found that there is a significant variation in the gut microbiome of Alaskan brown bears (Ursus arctos), depending on where the bears lived and what they usually ate. These findings shed more light on the complex relationship between wildlife habitat, diet, and gut microbiome diversity.

“The gut microbiome is the ecosystem of microbial life that populates an animal’s digestive system – and this microbiome plays a major role in an animal’s well-being,” said study co-author Erin McKenney, an assistant professor of Applied Ecology at the North Carolina State University. “Everything we learn about these microbiomes helps us make more informed decisions to support the health of wildlife species.”

According to study co-author Grant Hilderbrand, the associate regional director for resources for the National Park Service in Alaska, the habitats of Alaskan brown bears are currently changing. “The gut microbiome serves as a new diagnostic tool for understanding the health of wildlife populations. It can also help us predict how animal health will change as the environment changes. The study we’ve done here lays the foundation for advancing our understanding of gut microbiomes in Alaska’s iconic brown bears,” he explained.

The researchers analyzed the microbial DNA found in 66 fecal samples from 51 brown bears across three national parks and preserves (Katmai, Lake Clark, and Gates of the Arctic), and found significant differences in the diversity of the bears’ microbiomes at each of the three locations. 

“Katmai had the most diversity, and also had the most diverse array of food sources available. Gates of the Arctic, which had the most limited array of food resources, also had bears with the least diverse gut microbiomes. In other words, we found what we expected: the more diverse the diet, the more diverse the gut microbiome,” reported study lead author Sarah Trujillo, who worked on the study while a graduate researcher at NMU.

“However, while we found clear distinctions in microbiome diversity at each park, those differences could not be fully explained by diet alone. There appears to be something else at play that we don’t fully understand yet. That’s an area for future research,” she concluded.

The study is published in the journal PLoS ONE.

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By Andrei Ionescu, Earth.com Staff Writer