Report Summary

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Deep History

The grizzly bears that occupied Idaho for millennia—and continue to hold on in Idaho’s portions of the Selkirk, Cabinet-Yaak, and Yellowstone ecosystems—are members of a unique evolutionary and biogeographic lineage that has disappeared virtually everywhere else on Earth.

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Grizzly bears in Pleistocene Idaho were probably relegated to using marginal habitats, foods, and temporal windows as means of avoiding other predatory carnivores and obtained meat primarily by scavenging large-bodied herbivores in amounts likely to constitute an important food for many bears. Despite this, most grizzlies probably relied primarily on vegetal foods for the bulk of their diet, with whitebark pine seeds also of prominent importance.

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Pre-European Holocene

The Altithermal was probably a stressful period for grizzly bears caused by hot-dry conditions that reduced amounts of vegetal foods—including the abundance of whitebark pine—for perhaps as long as 3,500 years. By contrast, the generally cooler and wetter conditions that followed the Altithermal not only resulted in greater herbaceous productivity, but also an increased frequency of forest fires that likely resulted in greater amounts of available fruit on shrub species such as huckleberry and buffaloberry—both of which tend to flourish in more open conditions—and thus in the wake of forest fires.

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Grizzly bears in most parts of ancestral Idaho probably had access to abundant meat during the Holocene either from spawning anadromous salmonids or from large-bodied herbivores such as bison and elk, with these two sources complementary in both time and space. The challenges to grizzlies posed by humans, at least up until the arrival of European horses and then Europeans themselves, tended to be spatially concentrated along specific reaches of the Columbia and Salmon Rivers, leaving bears ample access to salmon in mountainous areas of central Idaho. There may even have been a brief Edenic time for grizzlies that lasted a couple of centuries between when European diseases took their toll on indigenous human populations and lethal Europeans arrived in person.

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The Arrival of Europeans

The future state of Idaho almost certainly supported several thousand grizzly bears at the time of European contact, with highest bear densities likely occurring in portions of the state north of the Snake River Plain. Central and northern ancestral Idaho were probably more productive environments for grizzly bears compared to the arid and semi-arid Snake River Plain, largely as a consequence of abundant fruit, anadromous salmonids, and whitebark pine. Central portions of the Snake River Plain may have only supported significant numbers of grizzly bears when bison roamed this region prior to the 1830s-1840s.

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Impacts of Europeans in nascent Idaho likely unfolded in pulses organized around different episodes of colonization and exploitation with different geographic foci. Traffic on the Oregon Trail probably unleashed an early devastation of fauna on the Snake River Plain during the 1840s-1860s. Miners flooded remote mountains of central and north-central Idaho during 1860s-1880s. Agriculture followed during the 1870s and 1880s, most dramatically on the Palouse Prairie where a native grassland that had previously supported bison was almost completely converted to non-native wheat. Barring the effects of subsequent dams on the Columbia and Snake Rivers, perhaps the most severe environmental impacts caused by European colonization played out during a remarkably brief 40-year period.

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Extirpations of grizzly bears from Idaho by newly-arrived Europeans were rapid, widespread, and anomalous, with some anomalies plausibly explained by the concentration of grizzlies near lethal people in pursuit of spawning salmon, but with prospects of mineral-related wealth also sending people into even the most remote refuges left to grizzlies. The massive wildfires of 1910 and the near end of chinook salmon spawning runs might have contributed to delivering a coup de grâce to the last grizzlies left in the Clearwater country.

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Prospects and Potential

Vacant wildlands of central and north-central Idaho currently have the potential to support as many as 1,000 grizzly bears which, if realized, would offer significantly greater odds of population persistence compared to if grizzlies were confined to the Selway-Bitterroot Recovery Area. However, long-term viability will require a contiguous interbreeding population of several thousand grizzly bears, which could be achieved if current populations were connected by on-going colonization of interstitial potential suitable habitat throughout the northern Rockies into Canada.

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Prospective Diets

Much has changed between 1800 and now in the tableau of grizzly bear foods. Whitebark pine is diminished everywhere and, in areas to the north and west, functionally extirpated as a bear food by white pine blister rust. The distribution of spawning habitat for anadromous salmonids has been truncated in Idaho by high dams on the Snake River above Hells Canyon. Surviving salmon and steelhead populations elsewhere in Idaho have been dramatically reduced by impediments posed by numerous dams on the lower Columbia and Snake Rivers. Even so, much bear food remains, with the fruit and forb-based dietary economy of north-central Idaho essentially intact.

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The current distributions of major bear foods together with diets documented for grizzly bears in nearby ecosystems provide ample basis for anticipating what grizzlies would likely eat in different parts of central and north-central Idaho, ranging from a dominance of fruit and forbs to the north, to greater contributions of elk and whitebark pine seeds to the south—with salmon and trout of possible importance in between.

Given the large sizes of adult chinook salmon, steelhead trout, and even bull trout—all often >4 kg—fishing by grizzly bears could probably be sustained in headwaters of the Clearwater and Salmon Rivers by even modest spawning runs—which could, in turn, result in salmonids playing a significant role in the diets of grizzly bears in central and north-central Idaho.

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There are clearly ample foods for grizzly bears on the Nez Perce-Clearwater National Forests, including potentially substantial amounts of meat from either salmonids or elk throughout the bears’ active season. During summer and fall, distributions of key foods will likely attract grizzlies to comparatively secure habitat, much of it in designated Wilderness Areas, whereas during spring productive habitats will probably attract grizzlies to lower elevations where conflicts with humans will be likely. Other conflicts could arise over foreseeable impacts of grizzly bear predation on iconic elk populations that some people see as existing primarily to provide a harvestable surplus for humans to kill.

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Security and Coexistence Infrastructure

Because of inattention to conflict prevention by state wildlife and federal land managers, current conditions on the Nez Perce-Clearwater Forests are ripe for grizzly bear-human conflicts over unsecured garbage and food; conflicts over livestock depredations; conflicts with big game hunters; and mortalities caused by black bear hunters mistaking a grizzly for a black bear. All of this promises to leave managers scrambling to deal with grizzly bear mortalities arising from foreseeable conflicts.

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Disregard for the best available science together with inexplicable variation in security standards among ecosystems complicate any assessment of whether conditions on the Nez Perce-Clearwater National Forests provide adequate security for grizzly bears—which is further complicated by being nested within the larger issue of what’s needed at a broader scale to insure population viability. But these sorts of complications do not debar an evaluation of landscape conditions and useful comparisons with other ecosystems.

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There is an imperative to reduce road access on the Nez Perce-Clearwater National Forests, not only because median levels of habitat security for grizzly bears are subpar, but also because measures to prevent conflicts are inadequate and likelihood of poaching and other illegal killing is comparatively high. In other words, heightened odds of prospectively lethal confrontations between humans and grizzly bears increases the need to reduce levels of contact through restrictive management of road access.

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Fragmentation

Natural colonization of north-central Idaho by grizzly bears will clearly depend on successful immigration of grizzly bears from the Selkirk, Cabinet-Yaak, and Northern Continental Divide Ecosystems. However, this on-going process will predictably proceed at a slow pace because of hazards created by I-90 to the north and human settlements in the Bitterroot Valley to the east. As much as natural colonization will depend on creation of in situ conditions that foster survival of newly-arrived grizzlies, it will also depend on making I-90 and the Bitterroot Valley more permeable to migrants. Fortunately, there is no shortage of knowledge and experience about how to do this, whether related to highway crossing structures  or human-grizzly bear coexistence.

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The Future

Dramatic increases in temperatures together with diminished snowpacks and substantial summer-time drying will predictably lead to deteriorating hydrologic regimes and increasingly frequent wildfires throughout most of Idaho. These and other environmental changes will almost certainly translate into foreseeable impacts on foods that are currently important to grizzly bears in Idaho’s potential suitable habitat.

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Emerging patterns in the Yellowstone and Northern Continental Divide Ecosystems foreshadow a future in which additional vegetal foods are lost and grizzly bears switch to alternate high-quality foods that catalyze local changes in distribution—a future in which meat from terrestrial sources plays a prominent dietary role, as it likely did at lower elevations in Idaho during the late Pleistocene and early to middle Holocene. If this future comes to pass, it will put human-bear relations increasingly to the test, especially when there are conflicts with livestock producers subject to depredation losses or hunters jealous of their peroprogatives to kill harvestable elk.

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Relations with humans will continue to dictate whether grizzly bears survive and thrive in the northern U.S. Rocky Mountains, including in the wildlands of Idaho. Yet relations with people have become increasingly typified by volatile dynamics at the juncture of human population increases, socio-economic change, political conflict, and unstable attitudes. The future of grizzlies will likely depend on whether human resentments and population increases are offset by the preservation of wild places and continued emergence of benevolent attitudes towards large carnivores.

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