In a 2013 study on forest land near Vail, Colo., researchers blamed human tourists and recreation for the smaller herd counts, down to several dozen head of elk from 1,000 in years past. One study showed that if a cow elk was disturbed 10 times during calving, no calves would survive.
To complicate matters, advanced technologies for mountain biking contribute to deeper exploration of natural areas. Mountain bikes with snow tires, for example, expand the season of riding to winter, when wildlife are most vulnerable.
Solutions include better management of trails used by mountain bikes, as well as restricting use on some trails, lowering any speed limits and permitting bike riders only on dirt roads.
One solution “is careful planning of the trail corridor and the design,” said David Wiens, executive director of the International Mountain Bicycling Association in Gunnison, Colo. “That’s where the agencies get involved and the wildlife specialists, who can come up with the proper location of the trail based on their expertise. In certain cases, there are seasonal closures for wildlife.”
Some mountain biking groups, though, continue to fight for access to excluded wilderness areas. A bill titled the Human-Powered Travel in Wilderness Areas Act, introduced earlier this year by Senator Mike Lee, Republican of Utah, would allow local managers to decide whether mountain bikes are appropriate in designated wilderness.
“What should keep people from doing it,” Dr. Servheen said, “is common sense and the belief that grizzly bears have a reason to be here and I have lots of other places to recreate.”
“I am not against mountain biking,” he said. “But we need to understand grizzlies don’t have any other place to go. It’s their living room.”