Grizzly Bear

Grizzly Bear Photo
The biggest threat to grizzly bears today is increased conflict with humans, as more people develop and use the bears’ natural habitat.
Julie Larsen Maher ©WCS

Grizzly bears are icons of the wilderness: beautiful, powerful, sometimes fearsome, but also vulnerable. Grizzly bears once occurred from the Mississippi River west to the Pacific Ocean, and from northern Mexico up to the northern coast of Alaska. Eating a variety of foods—plants, roots, berries, pine nuts, insects, fish (especially salmon), rodents, and occasionally large animals like elk and moose—they are able to live in diverse habitats including grasslands, forests, and mountains.

But human developments and activities like livestock grazing, mining, and hunting caused their demise from 98 percent of their historic range in the continental United States and reduced grizzly populations in Canada as well. In 1975, grizzly bear populations in the western U.S. were listed as a threatened species under the Endangered Species Act. Recently, the grizzly population in and around Yellowstone National Park was de-listed thanks to many conservation measures that allowed this emblematic group of bears to recover.

Fast Facts

Scientific NameUrsus arctos horribilis
  • Grizzlies have excellent senses of smell and hearing, but comparatively poor eyesight.
  • Most adult grizzlies weigh between 300 and 600 pounds, but some individuals in coastal areas can weigh up to 1,500 pounds.
  • Grizzly bear cubs are born blind, hairless, and tiny, weighing less than a pound.
  • Female grizzly bears have one of the lowest reproduction rates of any mammal in North America.
  • Sometimes returning to the same den, grizzlies ‘hibernate’ for about six months from late fall to spring, during which they may lose 30 percent of their body weight.


The biggest threat to grizzly bears today is increased conflict with humans, as more people develop and use the bears’ natural habitat. As people construct more roads in and around wild areas and build new homes in previously undeveloped areas, bears become displaced and are often shot when they are perceived as a threat. For instance, bears are often removed or killed when they eat or approach foods or garbage carelessly left out. Expanding roads and highways also fragment landscapes and isolate grizzly habitats. This can prevent genetic interchange among individual grizzly populations, an important factor for the species’ long-term viability.

WCS Responds

WCS is working to help people coexist with bears throughout grizzly bear range. We use non-invasive techniques to survey grizzly bear populations and identify their core habitat areas. In select areas, we place GPS collars on certain grizzly bears to determine where they cross highways and then help design underpasses for safer passage. In the Greater Yellowstone Ecosystem, we monitor energy development projects, predator-prey dynamics, and human-wildlife conflicts across the landscape to conserve natural areas and many of the species living within them. Our field studies established the scientific basis for expanding Canada’s Nahanni and Waterton Lakes National Parks as well as wilderness areas in Montana. WCS-Canada’s focuses on two sites: Nahanni and Crowsnest Pass. These areas in the southern Canadian Rockies are essential to maintaining an interconnected landscape of grizzly habitats from Yellowstone to the Yukon. Our work in Nahanni helped lead the Canadian government in 2009 to increase the size of this protected park by more than 10,000 square miles in order to conserve grizzly bears and other wide-ranging mammals.

WCS Projects

Corridor Conservation in the American West

Food, water, shelter, and the freedom to roam—these are the basic needs of wildlife. WCS-North America works to protect and interlink crucial wildlife habitats through field-based research, outreach, and policy.

From the Newsroom

Alberta’s Heritage of Wildlife & Headwaters Up for GrabsDecember 27, 2013

John Weaver, Senior Conservation Scientist with WCS-Canada, warns that the Alberta government’s draft Regional Plan for the South Saskatchewan, which would establish new Wildland Parks in about a quarter of the area, will be inadequate to conserving its vulnerable fish and wildlife populations and sources of precious water that are cherished by southern Albertans.

Rise in Roadkill Requires New SolutionsMay 16, 2013

The U.S. highway system includes more than 4 million miles of road. Roads crisscross even the most remote parts of the country, fragmenting habitat and causing regular encounters between motorists and wildlife.

Arctic Alaska’s Conservation ConundrumFebruary 2, 2012

WCS senior scientist Joel Berger reflects on how Alaska’s recent decision to cull an Arctic predator in order to protect its prey may redefine the ecosystem’s hierarchy in unforeseen ways.

Apex Predators: A Scary LossJuly 20, 2011

In a recent study, WCS Conservationist Joel Berger concludes that the loss of large predators in the wild may be humankind’s most pervasive influence on nature.

Mapping Montana for Climate ChangeJune 23, 2011

A WCS conservationist maps out a climate change survival plan for species living within Montana’s Crown of the Continent ecosystem.


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