"It's causing an uproar around here," said Sylvia Minthorn, who lives in a tribal housing unit near the swamp, where she used to play as a child.
She's seen grown men's hair stand on end when the shrieks commence.
Colleen Chance, a tribal housing authority employee, keeps a recording of the howls on her iPhone.
"It's kind of spooky," she said. "Some say it's foxes, some say it's a female coyote and some say it's Sasquatch. I don't know what it is."
Listen:
Or download MP3 here.
So far no one's pinpointed the source of the noise on this rugged 178,000-acre reservation that extends into northeastern Oregon's Blue Mountains