A new study co-authored by scientists from the U.S. Geological Survey and Montana Fish, Wildlife & Parks helps to identify where in the Bitterroot Ecosystem grizzly bears could call home through reintroduction or recolonization.

In the study, “Predicting future grizzly bear habitat use in the Bitterroot Ecosystem under recolonization and reintroduction scenarios,” https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0308043

the researchers predicted that grizzly bears would favor large wilderness areas and extensive multiple-use public lands in the region, especially in the northern part of the Bitterroot Ecosystem.

The research predicts that, over time, grizzly bears will move into the ecosystem, which spans part of Montana and Idaho, but exactly where and when they will arrive remains unknown. The study is a follow-up to previous research which predicted potential connectivity pathways among the existing grizzly bear populations in Montana.

“To help both people and grizzlies, wildlife managers need to know where they can expect grizzly bears to reestablish,” said Sarah Sells, lead study author and USGS research ecologist. “By using movement models we developed for a nearby population of grizzly bears, we were able to simulate where bears might choose to go in the Bitterroot of today.”

In fact, GPS collar data from bears that have moved near or across the Bitterroot Ecosystem on their own aligned well with the study’s predicted habitat use.

Grizzly bears disappeared from the Bitterroot Ecosystem by the 1950s because of over harvesting and habitat loss. In recent years, nearby populations of grizzlies have been increasing and expanding their range toward the Bitterroot. While the heart of the ecosystem is one of the largest wilderness complexes in the contiguous U.S., there’ve been some changes in the region since grizzlies were extirpated, namely a lot more people are there today.

Predictions of where grizzly bears may move are important to inform recovery efforts and to balance the well-being of bear populations and humans alike. Models like the one used in this study can help inform where to focus conservation and management efforts like habitat protection, public outreach, human-wildlife conflict prevention and mitigation of the effects of roads.

“Because there is no remnant backcountry population to start from in the Bitterroot Ecosystem, reestablishment is expected to involve the presence of some grizzly bears in the more human-populated landscapes between ecosystems,” said Cecily Costello, study co-author and Montana FWP research wildlife biologist. “By predicting where bears might be in the future, our goal is to help agencies and communities prepare now so that both people and grizzly bears will thrive.”

The study predicted differences in habitat use depending on how the grizzles arrive to the Bitterroot Ecosystem, which could directly inform recovery efforts.

Specifically, it predicted that if grizzly bears naturally recolonize the Bitterroot Ecosystem, their habitat use would be concentrated in Montana but over time become more uniform across the northern extent of the region in Idaho. If grizzly bears were reintroduced to the region by people, their habitat use would be more concentrated in east-central Idaho. Finally, if natural recolonization continues even if grizzly bears are reintroduced, their habitat use would be widespread across the northern half of the Bitterroot Ecosystem and surrounding areas.