If you’ve ever thought it might be nice to just sleep through February, good news: scientists have come one step closer to understanding how bears do it.
It’s long been known that bears slow down their cells’ energy use during the winter to survive on little food. But scientists recently discovered that it’s not just the bear’s own cells that make hibernation happen—bacteria in the bears’ guts play an important role in both putting on fat in summer and slowing down their glucose use in winter.
Biologists in Sweden partnered with the Scandinavian Brown Bear Research Project to take fecal samples from tranquilized bears in the summer and winter. These samples contained the collection of bacteria, or microbiome, that lives in the bears’ intestines and helps them absorb nutrients. Then they transferred the microbiome to lab mice with no bacteria in their guts to see how it affected how fast the mice gained fat tissue.
In the summer, bears chow down on a broad diet of salmon, insects, and berries. These foods don’t just give them fuel—some carry specialized bacteria that help them break down and absorb fat in their food. The researchers found that the mice with “summer bear” bacteria packed on more fat compared to mice given the winter microbiome.
In the winter, bears don’t eat for up to six months, and the diversity of bacteria species in their intestines dwindles. Lots of fat tissue tends to cause animals to keep sugar circulating in their blood—as in diabetes. Bears with extra winter fat were able to slow down their sugar consumption, but in the summer they could both gain weight and use glucose normally—an unusual and helpful adaptation.
Are there lessons we can take from the bear’s gut that we could use to help humans with diet problems? It’s possible. Here’s what the study author Fredrik Bäckhed, from the University of Gothenburg in Sweden, told Jonathan Webb of BBC News:
“I don’t think that this study will have direct implications for obesity, as the summer microbiota will make you fat and the winter insulin resistant.
“But perhaps we can find clues for treating malnutrition from the summer bacteria, and help patients with anorexic disorders – including cancer patients.”
For more on bears’ winter sleep, check out our guide to the bear essentials of hibernation.