People who flock to central Oregon’s hiking and biking trails can be deadly for one of the region’s most iconic large animals.

If an elk is startled by humans 10 times while she's pregnant or nursing, her baby is likely to die before winter is over, according to research from Colorado State University that's been cited for decades.

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But trail closures on public land to give the elk privacy during calving season often don’t work. Deschutes National Forest wildlife biologist Brock McCormick said he gets why people might ignore the signs.

“Can you think of a more benign activity than taking a walk or bike in the woods? But when you put it in the context of you being one of 500 people doing that same thing on the same day … it takes on a different context,” McCormick said.

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Elk calves recorded by trail cameras in Wallowa Whitman National Forest, Aug. 4, 2017. Courtesy of Oregon Wild

Elk face more humans than ever before and harsh winters while pregnant. When summer comes around, they run on a tight calorie budget.

“Sometimes the difference between surviving and not surviving for them is a matter of the handful of disturbance experiences,” McCormick said.

On one popular biking trail near Bend known as Middle Flagline, the closure signs during calving season were routinely ignored or even ripped down. Last year over a single week during the closure, trail cameras recorded more than 100 bikes. This year, though, the number of scofflaws caught on video during that same week dropped more than 90%.

McCormick credits the Deschutes Trails Coalition, an alliance between 30 groups representing various trail users, for maintaining the signs and spreading the word among bikers and hikers.

“I think it made a big difference that that message was coming from the community, and it wasn't just the Forest Service and saying no,” he added.