BAKER CITY — A herd of bighorn sheep appears to be thriving in the remote Burnt River Canyon in Eastern Oregon after they were reintroduced in the late 1980s.

The Baker City Herald reports the herd has grown from a low of 46 in 1997 to 65 counted this year, despite cougar predation and other factors.

State officials said that, in the past year, four of the Burnt River bighorns were killed by cougars, two were hit and killed by cars, one died from disease and three died due to unknown causes.

Burnt River bighorn sheep were wiped out in the early 1900s.

In 1987, the state reintroduced California bighorn sheep to the canyon. The original transplant consisted of nine ewes, four lambs and two rams that were caught from the Leslie Gulch herd along Owyhee Reservoir in Oregon.

The original herd of sheep grew to 22 ewes, six lambs and 18 rams, as counted in December 1996.

In January 1997, a supplemental group of eight ewes and one ram from Humboldt County, Nevada, were released in the canyon.

Nine sheep from the highly visible herd that roamed the slopes above Interstate 84 near Arlington were moved to the Burnt River Canyon in December 2007.

Jamie Nelson of the Oregon Department of Fish and Wildlife said workers count sheep in the canyon during the spring and winter each year to monitor the population, and determine causes of mortality.

In addition to documenting causes of death, Nelson said she and other ODFW staff track Burnt River bighorns to see if they come in contact with domestic sheep, which can transmit fatal diseases to bighorns.

Cougars also remain a threat to the herd.

The state estimates that cougar populations in the northeast region, which includes Baker County, increased from 6.2 cougars per 100 square miles to 10.5 cougars between 1994 and 2003, with a substantial increase occurring between 2001 and 2003.