Biologists Finally Found What's Hunting Grizzlies in Yellowstone — And It Shouldn't Be Possible
Wildlife Insider
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Seventy-four grizzly bears died across the Greater Yellowstone Ecosystem in 2025, the highest annual death toll ever recorded. But while human activity remains the leading cause of documented grizzly bear deaths, wildlife biologists are uncovering a disturbing pattern deep inside Yellowstone National Park. Some of the most dangerous threats to Yellowstone's grizzlies are other grizzly bears.
After decades of conservation efforts, Yellowstone's grizzly bear population has recovered to approximately 1,050 animals. Yet as the population grows, scientists are documenting deadly encounters between adult males, disappearing bear cubs, and an unexpected survival problem in some of America's most protected wilderness.
In May 2025, a female grizzly known as 1063 lost two of her yearlings to a larger male near Grand Teton National Park. Similar incidents involving Yellowstone grizzlies have raised questions about sexually selected infanticide, a natural behavior in which male bears kill offspring to increase their breeding opportunities.
Researchers studying grizzly bear mortality have also discovered a surprising difference in cub survival. Inside Yellowstone National Park, approximately 49% of cubs survive to independence, compared with roughly 83% in the wider recovery zone. Why would young bears face greater natural dangers in areas with fewer people?
This wildlife documentary explores the mysterious rise in Yellowstone grizzly bear deaths, the growing competition between bears, and the environmental pressures that may be changing their behavior. From declining whitebark pine forests and disappearing cutthroat trout to population density and territorial conflicts, scientists are examining several possible explanations.
The recovery of Yellowstone's grizzly bears is one of America's major wildlife conservation achievements. But with record mortality and increasing pressure on the ecosystem, researchers face a difficult question: has the grizzly population reached its natural limit, or is something changing in Yellowstone's wilderness?
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Biologists Finally Found What's Hunting Grizzlies in Yellowstone — And It Shouldn't Be Possible
Wildlife Insider
353,026 views
Seventy-four grizzly bears died across the Greater Yellowstone Ecosystem in 2025, the highest annual death toll ever recorded. But while human activity remains the leading cause of documented grizzly bear deaths, wildlife biologists are uncovering a disturbing pattern deep inside Yellowstone National Park. Some of the most dangerous threats to Yellowstone's grizzlies are other grizzly bears.
After decades of conservation efforts, Yellowstone's grizzly bear population has recovered to approximately 1,050 animals. Yet as the population grows, scientists are documenting deadly encounters between adult males, disappearing bear cubs, and an unexpected survival problem in some of America's most protected wilderness.
In May 2025, a female grizzly known as 1063 lost two of her yearlings to a larger male near Grand Teton National Park. Similar incidents involving Yellowstone grizzlies have raised questions about sexually selected infanticide, a natural behavior in which male bears kill offspring to increase their breeding opportunities.
Researchers studying grizzly bear mortality have also discovered a surprising difference in cub survival. Inside Yellowstone National Park, approximately 49% of cubs survive to independence, compared with roughly 83% in the wider recovery zone. Why would young bears face greater natural dangers in areas with fewer people?
This wildlife documentary explores the mysterious rise in Yellowstone grizzly bear deaths, the growing competition between bears, and the environmental pressures that may be changing their behavior. From declining whitebark pine forests and disappearing cutthroat trout to population density and territorial conflicts, scientists are examining several possible explanations.
The recovery of Yellowstone's grizzly bears is one of America's major wildlife conservation achievements. But with record mortality and increasing pressure on the ecosystem, researchers face a difficult question: has the grizzly population reached its natural limit, or is something changing in Yellowstone's wilderness?