The elderly man, a resident of Middletown in Lake County, was hunting wild pigs with three other men in the Yorty Creek day use area off of Hot Springs Road near the Dry Creek arm of the lake.
Cloverdale Fire Protection District engineer Peter Avansino said that at about 10:30 a.m., one of the hunters shot the pig with a rifle, and the hunters then tracked the wounded animal into a canyon.
"It got backed into a corner, charged the hunters and bit the man in his hand and upper leg," Avansino said.
The hunters then killed the pig.
One of the hunters hiked up to a ridge and called 911 on a cellphone, Avansino said.
A Cal Fire helicopter landed nearby, and rescue personnel hiked down to the injured hunter, secured him to a stretcher and carried him back up to the ridge.
The man was flown by REACH helicopter to Santa Rosa Memorial Hospital, Avansino said. His name has not been released.
The other three hunters left the scene with the dead pig.
In addition to Cal Fire and the Cloverdale Fire Protection District, the Sonoma County Sheriff's Office, U.S. Army Corps of engineers and the Geyserville Fire Protection District responded to the incident.