A recent study on the gut microbiome of Alaskan brown bears.Ursus arctos) demonstrates that microbial life in the guts of bears allows them to achieve similar size and fat stores while eating widely different diets. The work highlights the role of the gut microbiome in supporting health in wild carnivores.
“We think bears have simple digestive tracts, so it’s easy to slip into thinking they have a simple gut microbiome,” says Erin McKinney, co-author of the study and assistant professor of applied ecology at North Carolina State University. “But this study shows that there can be tremendous diversity in the gut microbiome among individual bears, and that this difference can be very important for the physical condition of these animals.”
“For example, the amount of fat that bears can store is critical to the health of wild populations,” says Grant Hilderbrand, co-author of the study and co-regional director of resources for the Alaska National Park Service. “If female bears can reach levels where fat levels are 19-20% in the fall, they will reproduce. And knowing that they can follow different nutritional pathways to reach these fat levels is a valuable idea.”
In this study, researchers collected fecal samples from 51 adult brown bears in three national parks: Katmai National Park and Reserve, Lake Clark National Reserve, and Gates Arctic National Park and Preserve.
Previous research has shown that the bears’ diet varies in each park. Lake Clark bears usually eat a lot of berries, salmon, and mammals, such as moose. Bears at the gates of the Arctic tend to eat seasonal plants and mammals, but they have no access to fish. The bears on the Katmai coast have the most diverse food landscape, including a variety of plants, fish and a wide variety of marine species.
“The fact that these populations have distinct diets is valuable, as it allows us to understand the role that the gut microbiome plays in helping bears extract nutrition from very different food sources,” says study author Sarah Trujillo. Student at Northern Michigan University (NMU).
“We found that bears benefit from having diverse food niches, and the gut microbiome plays a role in extracting nutrition from those diets,” Trujillo says. “Ultimately, this means that the bears in these parks were able to achieve very similar physical conditions, despite eating very different things.”
“Because parks are protected and well-protected environments, this study could serve as a baseline for future research,” says Diana Lafferty, study co-author and assistant professor of biology at NMU. “For example, researchers will be able to compare the gut microbiomes of bears in more disordered systems—such as areas where bears have greater access to litter and human foods—with the data from this study.”
“This study is also important because it gives us a quick glimpse into the bears and their diet in these parks,” says Hilderbrand. “The biggest conservation challenge we face now is climate change, and understanding what is happening now will help us identify and understand any changes that will occur in the future.
“Knowing what bears eat, and that these diverse diets can be used to reach similar body conditions, can help us identify emerging challenges for these animals. It can also help us understand how many bears are able to support these ecosystems, even as those ecosystems change. .”
“In short, this study gave us important insights into both the park ecosystems in which these bears live, and the microbial ecosystems that help these bears thrive,” McKinney says.
The study, “The influence of endogenous and exogenous factors on the gut microbiome of omnivorous animals,” will be published September 22 in the journal Open Access. Scientific Reports. The paper was co-authored by Kyle Jolly and Buck Mangipani of the National Park Service. Lindsey Mangipane, David Gustine, and Joy Erlenbach of the US Fish and Wildlife Service; and Matthew Rogers of the National Marine Fisheries Service.
The work was made possible by research funding from NMU.