California Grizzlies Weren’t as Big—or Bloodthirsty—as People Once Thought

The now-extinct bears were mostly vegetarians and measured about the same size as today’s North American grizzlies

A model of a California grizzly bear in a museum
A California grizzly bear specimen at the Santa Barbara Museum of Natural History. The brown bear subspecies went extinct around 1924. Vahe Martirosyan via Flickr under CC BY-SA 2.0 DEED

Historical accounts often portrayed the now-extinct California grizzly bears as huge, bloodthirsty beasts ready to pounce on humans and attack livestock at any time.

But while that probably made for some good stories, scientists say the truth may have been less dramatic: The bears ate a mostly vegetarian diet and were smaller than portrayed, according to a new paper published Wednesday in the journal Proceedings of the Royal Society B.

California grizzly bears (Ursus arctos californicus) once roamed the Golden State. But when European—and later, American—settlers began setting up farms there, they removed and fragmented much of the bears’ habitat. In addition, settlers often hunted, poisoned and trapped the creatures, which they viewed as dangerous livestock-killers. Some counties even offered bounties for the bears.

“They were built up as monsters that had to be overcome,” says study co-author Peter Alagona, an environmental historian at the University of California Santa Barbara, to the Atlantic’s Katherine J. Wu.

Over time, because of these human activities, the California grizzly population plummeted. The last reliable sighting of a California grizzly bear occurred 100 years ago in 1924, and the animals disappeared completely sometime after that.

Researchers wanted to get a better understanding of the factors that hastened the bears’ demise. They also hoped to gain more insight into the creatures’ behavior, size and diet.

To do so, they turned to archival documents—such as newspapers, diaries and other historical sources—and California grizzly specimens in natural history collections. They measured the animals’ skulls and teeth to get a sense of their overall body size, and they analyzed their bones and pelts for chemical elements that would indicate what the bears ate while they were alive.

California grizzly bears were about the same size as today’s living grizzlies—roughly 440 pounds—which is much smaller than the 2,000 pounds often reported at the time, the researchers found. Historical accounts may not necessarily have been wrong, but they might have only included the largest bears. Hunters likely targeted the biggest behemoths to earn more money and to boost their own reputations, according to the researchers.

In addition, analyses of the animals’ bones and pelts suggest the bears were primarily eating plants—both before and after Europeans arrived in the region in 1542—which stands in stark contrast to their fearsome, hyper-carnivorous reputation.

Pre-European arrival, 90 percent of the bears’ nutrition came from plants, and 10 percent came from animal meat, the researchers found. Those numbers did shift slightly with the proliferation of farming and ranching, with meat rising to account for 26 percent of the bears’ diet.

“The bears likely increased meat consumption due to landscape changes coupled with the arrival of a new source of protein—livestock,” says study co-author Alexis Mychajliw, a biologist at Middlebury College, to Live Science’s Sascha Pare. However, researchers found the animals still ate a majority vegetarian diet and killed far less livestock than historical accounts suggested.

Zooming out, the findings indicate that human activities can alter an animal’s behavior and diet. But these shifts can also lead to “exaggerated predation narratives” that “incentivize persecution, triggering rapid loss of an otherwise widespread and ecologically flexible animal,” the researchers write in the paper.

By digging beyond the bears’ reputation, the researchers gleaned a more accurate understanding of the California grizzly’s biology and natural history. And since scientists and land managers often rely on historical accounts when reintroducing animals to their former habitats, the study serves as a reminder that old newspapers and journals may not tell the whole story.

“Every piece of history you read about California grizzlies really describes them as being these monsters, incredibly large,” says Alex McInturff, an ecologist at the University of Washington who was not involved in the new paper, to Science’s Rodrigo Pérez Ortega. “So, to hear that they were just like the bears that you see now, that was pretty surprising to me.”

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