It's not an uncommon experience on the West's public trails. Pressed by other trail users, horses and their riders are finding themselves less welcome on some trails.
"Equestrians and hikers, once they experience the droves of bicycles on (multiple-use trails), quietly go elsewhere," says Berto, an equestrian representative on the Marin County Open Space and Trails Committee.
Mountain bikers aren't the only recreationists spooking horses and riders.
"The growth in off-road vehicles seems to be one of our biggest threats," says Edd Blackley, a Montana representative of Back Country Horsemen of America. "There's so many of them. Some horsemen are opting not to go (into the backcountry) anymore."
But not all equestrians are trotting away. Some are rearing up.
Back Country Horsemen, a 10,000-member group based in Graham, Wash., that advocates the recreational use of horses on public lands, is collaborating with public agencies, recreational groups and environmentalists to ensure that trails are shared peaceably. One tool: brochures on trail etiquette. Because the noise from an off-road vehicle can spook a horse, Back Country Horsemen suggests that drivers stop and turn off their engines until the horses pass.
"We can't exactly turn our horses off," says Blackley.