The Life of Grizzly 500

A Montana Fish Wildlife & Parks bear management specialist kept track of the same female grizzly for 21 years. Here are the highlights from his journal of Grizzly Bear 500. 

January 1979

In a snow-covered den high on a slope of the Rocky Mountain Front in Montana, a grizzly bear is born. The one-pound cub nestles in her mother’s fur. Nourished on rich milk, she grows rapidly. When she emerges from the den in late May with her mother, she weighs about 10 pounds. 

LEFT: Bear den. RIGHT: Grizzly sow and cub wandering through sagebrush in the Greater Yellowstone Ecosystem.

May 1983

At 4-1/2 years old, the youngster is captured for the first time on a ranch several miles from where she was born. She weighs 235 pounds and is nearly blonde, with darker brown legs. She is outfitted with a radio collar labeled “Grizzly Bear 500,” though she will eventually be named Bonnie, for the rancher on whose land she liked to roam.

LEFT: Rick Mace, FWP bear manager. RIGHT: Attaching a radio collar to a sedated grizzly bear.

June 1983 

Grizzly Bear 500 is seen traveling with a male grizzly. She is in estrus, meaning she is receptive to mating. Grizzly Bear 500 spends most of this year on plains and river bottoms west of Choteau, Montana. Her range is roughly 23 square miles. 

1984

At five years old, she has her first cubs: one female and two males. The family spends spring, summer, and fall on the prairie and along streams. Her range is now 35 square miles. In late October, the family enters a newly dug den for the winter. 

Painting of Grizzly Bear 500. Scenes from her life.

1985

Spring and summer are very dry. Grizzly Bear 500 and her one-year-old cubs get into trouble for the first time, raiding and damaging beehives near houses. The family is captured and moved 58 miles west to the other side of the Rocky Mountains. One male yearling dies from an injury sustained in the capture. Grizzly Bear 500 and the two remaining cubs are back two weeks later and do more damage to the beehives. On June 29, 1985, the bears are captured again and moved farther west, to the Mission Mountains 70 air miles away. Grizzly Bear 500 and her offspring are back by late summer. The beehives have been removed. A dry summer and little food cause her to roam and increase her range. She weighs 300 pounds, and her fur has turned dark brown, though her head and hump are still blond. There is no trouble with people this fall. 

LEFT: Sow with cubs. RIGHT: Grizzly bear damage to domestic beehives.

1986

Grizzly Bear 500 emerges from the den in April with her offspring, who are now two years old. Soon after emerging, she leaves the youngsters. Although she is not seen with a male, she probably mates this spring. The newly independent cubs stay together, raiding and damaging beehives. In May, the young female is captured under the porch of a ranch house and moved permanently to the Detroit City Zoo. The young male raids more beehives and then disappears. Using a signal transmitted from her radio collar, biologists keep track of Bonnie through the year until she dens. Her range is now 77 square miles. In October, while in the den, the radio collar quits. 

1987–1989 

Although her radio collar is not working, Bonnie probably remains in her home range along the Rocky Mountain Front. In the fall of 1988, a large female with her coloring is seen with a yearling. The beehives are now protected with an electric fence.

October 1989 

Bonnie is captured for the fourth time in 10 years. She has two cubs, and the family has been preying on sheep next to a ranch home. Bonnie is a fat 450 pounds. She is almost all brown, with only a golden head. The cubs are a healthy 120 pounds each. With a new radio collar, she and the cubs are moved 131 miles to the Montana-British Columbia border. She goes north into Canada and disappears in mid-October, probably into a den. 

1990 

In May, she appears with her yearlings back in Montana. She has a very strong homing instinct and has traveled over some of the roughest mountains in the United States to get back to her home range. In the summer, the female cub is killed, and the second cub disappears. 

Riparian habitat along the Rocky Mountain Front.

1991 

At 12 years old, Bonnie gives birth to two cubs, her fourth litter. It’s a dry summer. The bear family damages two bee yards, one without an electric fence and the other with an electric fence that isn’t working. The owners fix the fence; Bonnie ventures far to the east, away from the safety of the mountains, but stays out of trouble. 

1992 

Quiet, rainy year. The family does not have to roam far for food. 

1993 and 1994 

Bonnie separates from her cubs. The cubs play and travel together. No problems with people. A hidden camera takes her picture in the summer of 1994. Now 15 years old, she’s chocolate brown, heavy, and healthy. In the fall of 1994, she loses her radio collar. 

LEFT: Bear cub eating cow parsnip. RIGHT: Grizzly sow with cubs.

September 1998 to 2022 

Bonnie is captured for the fifth time, trapped on this occasion well outside the recovery line. She is 19 years old and has two small female cubs of the year. The year has been poor for chokecherries, and she has been damaging domestic beehives. She is relocated a short distance up along the eastern mountain front and is monitored for the next two years. This litter of cubs stays with her for two years. In 2000, she is observed breeding with a large male. 

Later that year, she is killed by a poacher who throws her radio collar into a river. In 2004, a federal case was made against the poacher, who was found guilty and paid a $2,500 fine. 

As of 2022, through genetic analysis of detected or captured bears, we know Grizzly Bear 500 produced at least one female offspring, who was last captured in 2014 and is not known to have died. This female has also produced at least two cubs (a male and a female) that made it to adulthood and were captured or detected. The female (500’s offspring’s offspring) is not known to be dead but was last observed in 2004. The male offspring died in a management removal as a 7-year-old due to breaking into sheds for livestock feed.

This story is an excerpt from Grizzly Bears of Montana, a resource guide for educators. In partnership with Montana Fish, Wildlife and Parks, the Boone and Crockett Club produced this interactive book that includes six illustrated chapters, including puzzles and games. 

 

Grizzly Bears of Montana, Second Edition

Montana is bear country, with the grizzly bear being the official state animal. Grizzly bears in Montana are an iconic native species with high value to people and cultures across the state and around the world, and they play important roles in Montana ecosystems and economies. Today, Montana has the largest remaining grizzly bear population in the lower 48 states.

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