Grizzly Bears in the Greater Yellowstone Ecosystem

/

Whitney Tilt, Conservation Chatterm June 23, 2017. Rangemap updated in 2023.

Gfrizzly bear in Yellowstone national park (jim peaco, public domain)

STATUS

The Grizzly Bear (Ursus arctos) once roamed much of western North America. Presently it is found in five distinct populations in the conterminous United States, including the Greater Yellowstone Ecosystem (GYE), see map. The species has been listed as threatened with extinction under the Endangered Species Act (ESA) since 1975. Since its listing, a great deal of effort has been made to conserve the species including removal of livestock, especially sheep, from the GYE recovery area; clean-up and lock-up of garbage and other bear attractants; and stronger education and law enforcement to prevent accidental shootings and poaching. While most would agree that substantial progress has been made, there is a great deal of disagreement surrounding the bear’s status and whether to delist the species in the GYE.

In 1993, a recovery plan was implemented with three specific goals that had to be met for six consecutive years. In 2003, those recovery goals were met and the U.S. Fish and Wildlife Service (FWS) proposed to delist the bear in 2005. The proposal was shelved after significant resistance from environmental interests, and the recovery plan was modified with updated population and mortality methodologies. The GYE population continued to meet recovery goals and was removed from the ESA in 2007. Lawsuits were immediately filed and in 2009 a federal district judge overturned the delisting and put the species back on the threatened list. The judge ruled that 1) the Conservation Strategy, under which the bear would be managed by state and federal agencies, was unenforceable; and (2) the FWS did not adequately consider the impacts of the potential loss of whitebark pine nuts, a grizzly bear food source.

Map courtesy of Interagency grizzly bear committee

Responding to the 2009 decision, an Appeals Court ruled in 2011 that the Conservation Strategy did, in fact, provide an adequate regulatory mechanism, but upheld the lower court’s ruling on whitebark pine and other foods.

In 2013, the Yellowstone Ecosystem Subcommittee, the Interagency Grizzly Bear Committee, and Interagency Grizzly Bear Study Team again recommended the species be removed from the threatened species list, specifically adding that alternative foods are available and the reduction of whitebark pine did not appear to have a significant impact on bears.

In March 2016, FWS again proposed to remove the species from the ESA, by reason of recovery. On June 22, 2017, the Department of the Interior announced that the Yellowstone population of the grizzly bear has recovered to the point where federal protections can be removed and overall management can be returned to the states and tribes.

DOI concludes the population has met and exceeded all criteria for delisting, including: 1) estimated population size, 2) distribution of females with cubs, and 3) mortality rates.

1.       Population Recovery target: ≥ 500 bears in the recovery area (criteria instituted in 2014): achieved in 2014 and 2015. In 2015, there were an estimated 717 grizzly bears in the GYE, an increase from 136 in 1975.

2.       Distribution Recovery target: Objective of 48 females producing cubs annually: achieved since 2006. Earlier target was female grizzlies with young occupying at least 16 of the 18 bear management units that comprise the Primary Conservation Area in the GYE. This goal has been met since 1998.

 3.       Mortality:

a) Estimated percent of total mortality of independent-aged females not to exceed 7.6% (lowered from 9% in 2012): achieved 2006-07, 2009-10, 2012-14.

 b) Estimated percent of total mortality of independent-aged males not to exceed 15%: achieved 2006-07, 2009, 2012-15.

 c) Estimated percent of mortality from human causes for dependent young not to exceed 7.6% (lowered from 9% in 2012): achieved 2006-15. Earlier standard was bear mortality must be limited to no more than 4 percent of the total population. This goal has been met since 1996 with the exception of one year.

  •  In 2015, there were 59 known and probable grizzly bear mortalities in the GYE: 34 attributed to human causes; 4 of undetermined cause; 2 were natural deaths; and 19 unknown.

While there are plenty of opinions on all sides, the primary concern by opponents to delisting is the fear that protection for the GYE grizzlies will disappear if they are taken off the ESA list. In fact, years of effort have gone into crafting a conservation package for Yellowstone’s grizzlies to ensure that the bears continue to thrive once taken of the list. Developed by federal and state natural resource management agencies, the Conservation Strategy provides an impressive set of protections including a six-million-acre core Primary Conservation Area, protections against excessive take, and extensive monitoring. A solid framework is in place to ensure that continued grizzly bear conservation will follow delisting. As the needs of Yellowstone grizzlies change or increase, so will the tools and protections needed to meet them.

Outside the courtroom and the court of public opinion, management of bears changes little whether it is listed under the ESA or not. Land agencies will continue to manage the bear and scientists will continue to monitor the long-term recovery goals, and members of the public will sit in judgement.

BEING SMART IN GRIZZLY COUNTRY

In 2015, a human-grizzly conflict inside Yellowstone National Park resulting in one dead human, the killing of the mother grizzly, and removal of two, now-orphaned cubs to a zoo. This event was tragic for humans and bears alike. Humans deaths from grizzly attack are rare, especially in light of the number of potential interactions of grizzlies and humans as they overlap in time and space. In Yellowstone National Park, the number of bear-inflicted human injuries has averaged less than one injury per one million park visits each decade from 1970 to 2014. From 1980 to 2014, 37 people were injured by grizzly bears in Yellowstone (an average of 1.1 injuries per year).

Grizzly bears can be dangerous.  Considering their size, strength, and potentially aggressive nature, it is remarkable that they don’t injure or kill people more often than they do. To be prepared one must take responsibility for their own safety in grizzly country.  The following advice is compiled from People and Carnivores:

  • The most important tool for staying safe is situational awareness -- "knowing what is going on around you." 

  • Pay attention to where you are – can you see very far?  Is there terrain or vegetation that could hide a bear from your view?  Many people have an unrealistic ‘search image’ -- they assume that grizzlies are huge, and therefore easy to see.

  • Be aware of wind direction. If the wind is in your face as you walk, that means your scent is being carried away from any bears that may be ahead of you. In our experience, grizzlies that can catch your scent will typically leave once they know what you are.

  • Stay alert for fresh bear sign as well. Tracks may not always be obvious – look also for scat, rub trees, or fresh digging (excavating roots, insects, or rodents).  Bears will often tear apart logs or flip rocks seeking food.·         One of the most dangerous situations to walk into is a grizzly that has claimed an animal carcass.  The bear’s inclination will be to defend this food source.  Look and listen for scavenger birds like ravens and magpies.   You may be able to smell a carcass from some distance if the wind is right.  If you do detect a carcass, take a wide detour around it, or turn around if there is no option to detour.

  • Bears tend to be most active at dusk and dawn, but that doesn’t mean you can’t encounter one in midday.  Bears often sleep during the day in thick timber.  Move carefully, and stop frequently to listen, when travelling through such places.

  • Have bear spray and know how to use it. Bear Pepper Spray is a highly effective, easily used deterrent against aggressive bears and other animals.  To use bear spray:

    • Remove safety clip

    • Aim slightly down and towards the approaching bear.  Adjust angle for wind direction.

    • Spray a brief shot when the bear is roughly 30 feet away.

    • Spray again if the bear continues to approach.

    • Once the animal has retreated or is busy cleaning itself, leave the area as quickly as possible, but do not run.  Alternately, go to an area of safety, such as a car.

    • REMEMBER: Bear pepper spray is only effective when used as an airborne deterrent sprayed as a cloud at an aggressive animal.  It should not be applied to people, tents, packs, other equipment or surrounding area as a repellent.

Many aggressive encounters with grizzlies happen very quickly.  Some are probably too instantaneous for a person to be able to react with either bear spray or a firearm.  To give yourself a margin of safety, carry your bear spray in a consistent and accessible place on your person (or on your saddle if you are horseback and prefer it not be on your person). Practice reaching for the spray until it becomes second nature to reach for it.

Courtesy of Center for Wildlife Information – Graphic Art Fund

GRIZZLY FACTOIDS

APPEARANCE. The grizzly bear’s color varies from blond to black, often with pale-tipped guard hairs (hence the name “Grizzly”). The coloration of black and grizzly bears is so variable that it is not a reliable means of distinguishing the two species (see comparison of grizzly and black bear below).

DIET. Bears are omnivores with a wide ranging and flexible diet, consuming different foods depending on location and season. Preferred foods include army cutworm moths, whitebark pine nuts, ungulates (elk, bison), and cutthroat trout. Bears in the GYE are known to consume at least 266 species of plant (67%), invertebrate (15%), mammal (11%), fish, and fungi. They will readily eat human food and garbage where they can get it. Their caloric requirements are: normal (May-Sept): 5,000-8,000 kcal/day; hyperphagia (a determined push for calories in advance of hibernation): 20,000 kcal/day; hibernation 4,000 kcal/day.

HIBERNATION. Grizzly bears hibernate in response to seasonal food shortages and cold weather. The location and nature of dens is variable, but typically dug in sandy soils, at base of large trees, on north-facing slopes (30-60 percent grade) at 6,500-10,000 feet elevation. In hibernation, body temperatures fall some 12 degrees F, slowing their metabolism by 50-60%. Bears sometimes awaken and leave their dens during the winter, but they generally do not eat, drink, defecate, or urinate during hibernation. They live off of a layer of fat built up prior to hibernation, and will lose some 15-30% of their body weight.

EMERGENCE. Bears emerge from their dens as temperatures warm and winter-killed ungulates and early spring vegetation become available. In the GYE, bears begin to emerge from their den in early February, and most bears have left their dens by early May. Males are likely to emerge before females.

REPRODUCTION. Female Grizzly bears (sows) rarely breed before age four, and the average age of first reproduction in GYE is 5.8 years. Once of reproductive age, females typically become pregnant once every three years. Implantation of a fertilized egg in the uterus is delayed so the embryo does not begin to develop until late November or December, about one month after the sow has denned. In late January or early February, the sow gives birth to 1-2 cubs, sometimes three, rarely four. At birth the cubs are hairless and blind, are about eight inches long, and weigh 8-12 ounces. The cubs do not hibernate but nurse and sleep next to the mother. At 10 weeks, the cubs weigh about 10–20 pounds. Male (boar) bears take no part in raising cubs, and may actually pose a threat to younger bears (see mortality). Grizzly bear cubs usually spend 2½, and sometimes 3½ years with their mother before she or a prospective suitor chases them away so that she can mate again. Females frequently establish their home range in the vicinity of their mother, but male cubs disperse farther.

GENUS/SPECIES: Ursus arctos is the North American Brown Bear, or Grizzly. Ursus (Latin for “bear”) and arctos (Greek for “bear”). There are several distinct subspecies including the Mainland Grizzly, U. arctos horribilis, found in the lower 48 states and the Kodiak bear, U. arctos middendorffi, on Kodiak Island, Alaska, the largest of the brown bear subspecies.

COMMON NAMES: grizzly bear, brown bear, silvertip.

LIFE SPAN: 20-30 years; oldest known in GYE 31 years.

SPEED: 35-40 mph.

CLAW LENGTH: average 1.8 inches (45 mm), longest 5.9 inches (150 mm); claw length and shape allow efficient digging of foods from the ground but are less efficient for tree climbing than black bear claws.

TREE CLIMBING ABILITY: cubs and younger, smaller bears are proficient tree climbers; however, adult male and female grizzly bears are also capable of climbing trees.

BODY TEMPERATURE: 98-101°F (36.5-38.5°C) during active season; 94-95°F (34.4-35°C) during hibernation.

RESPIRATION: 6-10 per minute; <1 per minute during hibernation.

HEART RATE: 40-50 beats per minute; 8-19 beats per minute during hibernation.

VISION: on par with human vision; exhibits color vision and excellent night vision.

AVERAGE WEIGHT: adult male = 413 lb. (187 kg); adult female = 269 lb. (122 kg).

AVERAGE HOME RANGE SIZE IN GYE: males = 337 square miles (874 km2); females = 109 square miles (281 km2).

GESTATION: 235 days (implantation of embryo delayed until late November/early December).

BIRTH PERIOD/LOCATION: late January/early February in winter den.

DEN ENTRY: pregnant females- 1st week November; other females- 2nd week November; males- 2nd week November.

AVERAGE DENNING DURATION: females with cubs- 171 days; other females- 151 days; males- 131 days.

DEN EMERGENCE: males- 4th week March; other females- 3rd week April; pregnant females- 4th week April.

TYPICAL DEN TYPES: excavated (i.e., dug) = 91%; natural cavity = 6%; snow = 3%.

PERIOD OF MATERNAL CARE: 18 to 42 months; average = 30 months.

SURVIVAL RATE: cubs = 55%; yearlings = 54%; subadults = 95%; adult females = 95%; adult males = 95%

CAUSES OF MORTALITY (GYE): Human-caused (including management actions, hunter-related, vehicle-strikes, etc.) = 85%; Natural causes (including male grizzly attacks, malnutrition) = 15%.

 Everyone likes to watch bears: bear watching enroute to the chapel in Grand Teton National Park, photo © P.Potter

Everyone likes to watch bears: bear watching enroute to the chapel in Grand Teton National Park, photo © P.Potter

SOURCES & RESOURCES

2016 Conservation Strategy for Grizzly Bear in the Greater Yellowstone Ecosystem. U.S. Fish and Wildlife Service. 128 pages.

Grizzly Bear Recovery in the Greater Yellowstone Ecosystem. Yellowstone Science 23(2): December 2015. 98 pages.

People and Carnivores. www.peopleandcarnivores.org