The grizzly bear (Ursus arctos horribilis) is a subspecies of brown bear and a major apex predator in western North America. Its presence is considered a sign of a healthy, functioning ecosystem. In the contiguous United States, the grizzly bear is listed as a threatened species. The population once estimated at 50,000 individuals across the American West has been drastically reduced. Today, the total population in the lower 48 states is estimated at approximately 1,900 bears, confined to a fraction of their historical territory. This dramatic decline is the result of centuries of human pressure, beginning with a campaign of eradication that pushed the species to the brink of extinction.
Historical Causes of Population Decline
The catastrophic collapse of the grizzly bear population in the 19th and early 20th centuries was primarily due to deliberate extermination efforts. As European settlement rapidly moved westward, grizzlies were viewed as a direct impediment to agriculture and livestock grazing. This led to widespread, unrestricted hunting and poisoning across the Great Plains and into the Rocky Mountains.
Government-sponsored programs actively encouraged the killing of grizzlies through bounty systems. These predator control measures effectively eliminated the species from 98% of its original range in the lower 48 states by the 1930s. The population was reduced to just a few hundred bears, isolated within remote wilderness areas and national parks like Yellowstone and Glacier. The combination of lethal control and habitat conversion nearly ensured the species’ complete extirpation south of Canada.
Ongoing Habitat Fragmentation
While direct killing has been curtailed by federal protections, the remaining populations face a persistent threat from habitat fragmentation. Infrastructure development, particularly the proliferation of roads and motorized vehicle use, fragments the landscape. Roads increase human access into remote areas, which is directly correlated with a higher risk of human-caused bear mortality, including vehicle collisions and illegal kills.
Studies in ecosystems like the Greater Yellowstone (GYE) suggest that female grizzly bear survival rates decline in areas where road densities exceed one mile per square mile. This fragmentation creates isolated “genetic islands,” such as the GYE population, which is physically and genetically separated from the larger Northern Continental Divide Ecosystem (NCDE) bears. Wildlife corridors are necessary to allow for the movement and genetic exchange crucial for the long-term health of the species.
The availability of food sources is another environmental pressure exacerbating habitat issues. The high-elevation whitebark pine, whose large, fat-rich seeds are a critical food source for bears preparing for hibernation, is collapsing. This collapse is due to a combination of climate change, mountain pine beetle infestations, and the non-native fungal disease, white pine blister rust. Loss of this reliable food source forces grizzlies to lower elevations and into areas of greater human development, directly increasing the risk of conflict and death.
Human-Grizzly Conflict
Direct, fatal interactions with humans are the leading cause of death for independent adult grizzly bears in the lower 48 states, accounting for over 70% of known mortalities in some recovery zones. These conflicts often arise when bears are drawn to human attractants, particularly during the fall hyperphagia period when they are desperately seeking calories. Improperly stored garbage, pet food, bird feeders, and livestock carcasses train bears to associate people with food rewards.
Bears that become habituated to human food sources are deemed “problem bears” and often face management removal. Wildlife agencies may attempt relocation, but repeat offenders are typically euthanized to prevent future threats to public safety or property. Livestock depredation is a significant driver of these removals, as bears that kill cattle or sheep on grazing allotments are often targeted for lethal control.
The concept of “social tolerance” significantly impacts conservation efforts, as the long-term survival of the grizzly depends on the willingness of people to coexist with them. Economic concerns over livestock loss and fear of personal safety are major factors that reduce this tolerance. When conflict rates are high, the local appetite for grizzly bear presence diminishes, making conservation efforts more difficult and leading to increased pressure for agency removals.
Current Conservation Status and Recovery
Grizzly bears in the contiguous United States have been listed as a threatened species under the Endangered Species Act (ESA) since 1975. This federal protection is the primary legal mechanism governing their management and recovery. The listing established six recovery ecosystems, with the GYE and NCDE representing the largest and most successful populations, each now exceeding 1,000 bears.
The recovery success in these two ecosystems has led to ongoing discussions and legal battles over potentially removing ESA protections. However, the overall status remains vulnerable due to the small, isolated nature of other populations. Managers continue to focus on education, securing human attractants, and monitoring bear movements to mitigate conflict and ensure population growth. The greatest challenge remains reconnecting the isolated populations to ensure long-term genetic viability across their limited range.