For A Brief Time In 1940, Monkeys Were Loose In Yellowstone

Yellowstone has always had a diversity of wildlife within its borders. Back in 1940, monkeys were briefly a part of the ecosystem.

Mark Heinz

August 26, 20234 min read

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Long before smartphones and social media made it much more difficult to get away with wildlife monkey business in Yellowstone National Park, a pair of elusive primates caused quite a stir there.

When a tourist asked Ranger Gorge Kennaugh where she could “see the rest of the monkeys in Yellowstone Park,” he thought she had to joking — or delusional.

But she was telling the truth.

It was July 1940, and there actually was a pair monkeys running loose in Yellowstone.

And even nearly 80 years later, some people still believe that the Gibbon River that runs through the park was named after the small ape, even though it wasn’t. It’s named for an Army general.

Newspaper Reports

The best accounts of the wayward primates come from reports in the Powell Tribune newspaper published in early August 1940.

According the one of those reports, when Kennaugh at first refused to believe the woman, she became “indignant, said that she knew a monkey when she saw one, and had just observed two small monkeys scamping through the pine trees along the highway within several hundred yards of the ranger station.”

Turns out she was right.

After some digging, Kennaugh discovered that two monkeys had in fact recently escaped from traveling zoo nearby.

And the frisky primates had apparently decided to take advantage of the opportunity to explore Yellowstone’s wonders, according the newspaper report.

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‘Monkey Hunt’

A follow-up article states that a “monkey hunt” for the wayward primates was still on 11 days later, and that their owners had posted a $50 reward for their safe return.

“A reward of $50 for their capture, posted by the owners, has sent the nearby community of Silver Gate on an unprecedented monkey hunt,” according to the Powell Tribune from Aug. 8, 1940.

“Although the two primates have repeatedly raided the community for food, lures ranging all the way from bananas to coconuts have failed to trick them back into captivity,” according to the article.

There’s no account of whether the monkeys were eventually captured or if they disappeared and eventually met their fate through a wild predator, inclement weather or some other misfortune.

At the time of the report, the monkeys had apparently survived “several nights of below-freezing weather,” according to the newspaper article.

Little Else Known

National Park Service historians have verified that those newspaper accounts were true, but virtually nothing else about the monkey incident is known, including their ultimate fate, agency spokeswoman Linda Veress told Cowboy State Daily. 

“It looks like there isn't much information to provide about the monkeys, except that there was a report on July 25, 1940, that they had escaped an itinerant zoo,” she said.

Gibbon River Named After Army General, Not Apes

Regardless of whether they made it back safely or died in Yellowstone, the monkeys left a lasting legacy — a persistent rumor that the Gibbon River was named after them.  

But that’s not true.

Brown also recounted that a few years ago during a winter tour of Yellowstone, he was told by a snowcoach driver that the Gibbon River had been named after the primate species, Gibbons.

That’s because, supposedly, “several monkeys” at one time had escaped and gone cavorting along the riverbanks, Brown said he was told.

But the most reliable reports recount only two monkeys, Veress said, and the river wasn’t named after them.

“The Gibbon River was not named after a primate,” she said. “It has been known as the Gibbon River since as early as 1877. It was named after Gen. John Gibbon, who had been in charge of the Army troops in Montana territory when the Hayden Expedition came through in 1871.”

Mark Heinz can be reached at

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Mark Heinz

Outdoors Reporter