What a Bear's Gut Reveals: Brown Bear Microbiomes in Three Alaska Parks

Inside every animal's digestive tract lives a whole ecosystem of microorganisms — the gut microbiome. It helps its host draw energy from food, tunes the immune system and keeps the animal healthy. Scientists increasingly see its importance for health, but its role in wildlife ecology and conservation is still largely unexplored.

In a large collaboration, National Park Service scientists and partners studied the gut microbiomes of brown bears (Ursus arctos) in three Alaska parks and preserves — Katmai, Lake Clark and Gates of the Arctic — using DNA.

How it was done

The team took subsamples of bear droppings collected during Park Service research in the three parks, extracted the microbes' DNA and sequenced a marker gene (16S rRNA) to identify which microbes were present. They then compared the variety of microbes within each bear and the differences between bears by location, season, sex and reproductive condition, and checked the results against standard measures of bears' body condition.

Where you live shapes what lives in you

• Katmai bears carried the most diverse gut microbes; Gates of the Arctic bears the least.
• Diversity fell the farther inland a park lay.
• Location and diet, the researchers concluded, drive the differences.

The likely reason is the menu. Katmai bears live near the coast and can eat both land and marine foods — sedges from coastal salt marshes among them, which bears in Katmai and Lake Clark can reach but bears in the Brooks Range cannot. A bear in the Brooks Range simply has fewer options.

Different diets, same condition

Among healthy bears, the gut microbiome showed no significant difference with body condition, and microbe diversity did not track body condition either — only very large bears had somewhat different microbiomes. That supports earlier findings that bears can reach the same body condition (the percentage of their body that is fat) on very different diets in very different places: the microbiome reflects each population's foraging strategy.

Why it matters

Checking bears' gut microbiomes could give wildlife managers a quick way to detect disturbances and judge how they affect brown bear health.

Sources

• National Park Service, "What we can learn from a bear's stomach." https://www.nps.gov/articles/000/a-bears-gut.htm
• Trujillo, S.M., McKenney, E.A., Hilderbrand, G.V., Mangipane, L.S., Rogers, M.C., Joly, K., Gustine, D.D., Erlenbach, J.A., Mangipane, B.A., and Lafferty, D.J.R., 2022, Intrinsic and extrinsic factors influence on an omnivore's gut microbiome: PLOS ONE 17(4): e0266698.
• Trujillo, S.M., and others, 2022, Correlating gut microbial membership to brown bear health metrics: Scientific Reports 12: 15415.
• Coverage: North Carolina State University news release, September 22, 2022.
• Photo: NPS / Jim Pfeiffenberger.
• Words on this page from people and organisations outside the federal government are paraphrased; rewritten in hubnx's own words.