The poaching is considering a contributing factor to a decline in the state mule deer population, which has fallen to 216,000 animals from historic peaks of more than 300,000.
Research supervisor DeWayne Jackson in Roseburg said poachers typically kill female deer, which are more important to reproduction. Licensed hunters kill more bucks than does.
"If we look at the illegal take, it's basically equal to the legal take — it's bad," said Michelle Dennehy, a Fish and Wildlife spokeswoman in Salem. "Poaching is not ethical, it's not hunting."
State biologists discovered the level of poaching during a five-year research study of deer between Bend and the California border, The Oregonian reported. The state study of 500 mule deer fitted with radio collars was conducted between July 2005 and last January.
Researchers said 128 deer died during the study. Of those, poachers killed 19 and hunters legally shot 21. Cougars killed 15 and eight were hit and killed by cars.
Of the rest, five succumbed to coyotes, disease claimed five and four others died while tangled in fences or from some other accident, Jackson said.
Biologists listed 51 as "cause of death unknown," but poachers could have taken some of those, he said. "Sometimes we just find the radio collar laying out in the sagebrush," he said.
Because the study wasn't designed to detect poachers, biologists don't know if other areas have comparable numbers of deer taken illegally, said Don Whittaker, Fish and Wildlife ungulate coordinator.
But wildlife managers suspect poaching is happening across Oregon.
Poaching "is out of hand in Oregon," said Ken Hand of Klamath Falls, regional director of the 11,000-member nonprofit Mule Deer Foundation based in Salt Lake City. "It's going on all over the state, 365 days a year. From all the contacts I have around the state, I just hear about it constantly."
The chance of Oregon's mule deer population ever rebuilding seem pretty slim "with the predators out there, including the humans," he said.
Oregon mule deer are native to the state and typically found east of the Cascade Range crest. Wildlife managers say the deer are under intense pressure from predators, including an estimated 5,700 cougars roaming Oregon's forests and high deserts, up from 2,600 two decades ago.
Oregon also has 25,000 black bears, and Canadian gray wolves have staked claim to the state's northeastern corner. All three species prey on mule deer.
Automobiles, too, account for plenty of mule deer deaths. A Fish and Wildlife study documented 1,626 mule deer killed by motor vehicles along 150 miles of U.S. 97 and Oregon 31, south of Bend, between October 2005 and January.
Dennehy said habitat issues are also a concern in central Oregon, where resort development, new homes and other human activities have sharply reduced winter range for mule deer.
It's difficult to catch poachers in the act, said Oregon State Police game officer Chris Hawkins of La Grande.
Many areas simply don't have many officers, he said. Wallowa County, which is the size of Delaware and Rhode Island and has a population of 7,150, has three game officers, Hawkins said.
Dennehy said the Oregon Hunters Association's "turn-in-poachers" program, or TIP, offers rewards, but that won't cure the problem.
"It's a very vast landscape," Dennehy said. "We can't have eyes everywhere."
Information from: The Oregonian, http://www.oregonlive.com
Copyright 2010 The Associated Press.