Endangered mountain caribou have unique gut microbes linked to lichen diet

Endangered mountain caribou in British Columbia possess a unique gut microbiome in late winter when they feed on tree lichens, a finding that could guide caribou recovery efforts, according to a new study from the University of Alberta.

Biologists examined the microbial composition of fresh caribou feces using advanced DNA sequencing technologies. They identified both what the caribou ate and the microbes in caribou guts that help digest their food.

The researchers compared samples from endangered deep-snow caribou to caribou in three other regions, including the mountains in Alberta, where snow is shallower in winter and caribou eat ground lichens. They also looked at the diets of pregnant caribou that were captured and placed in pens to protect them from predators during calving season, a practice used for several B.C. herds that is now being planned for caribou in Jasper, Alberta. They compared all three groups of wild caribou to domesticated caribou in Alaska.

The study, published recently in the journal Molecular Ecology, showed that mountain caribou in the high mountains of interior B.C. feed on different lichens than caribou east of the mountains, in Alberta. They also have different gut microbes.

"This shows that endangered mountain caribou really specialize in tree lichens and even have different gut microbes to digest them," says Scott Sugden, currently a Ph.D. student at McGill University and lead author of the study. The study also found that caribou in pens consumed different lichens than their free-ranging counterparts, partly because it is difficult for volunteer lichen collectors to identify and collect the same lichens that caribou choose and because penned caribou are also fed manufactured pellets.

The study has implications for efforts to save the dwindling herds of endangered caribou, which increasingly involves penning caribou. "This practice appears to lead to a pretty quick shift in gut flora, with unknown consequences for caribou health," says Toby Spribille, an associate professor at the University of Alberta who specializes on lichen and was the senior author on the paper.

"Saving an endangered species really requires that we understand and provide its preferred food. For B.C.'s mountain caribou, that means maintaining forests of the right age, especially old-growth forests, and characteristics to grow crops of the hair lichens that caribou rely on to get through the winter," Spribille says.

Taking caribou off their preferred food during calving season could be risky, says Colleen Cassady St. Clair, another senior researcher on the study. "Deep snow caribou have highly specialized diets and the alignment between those diets and the composition of their microbiome might be especially important during the calving period when novel food sources might compromise calf nutrition and development."