The 65-year-old man, identified as Marion Williams, had walked from his trailer in Humboldt County to a water source about 100 yards (meters) away on Oct. 8 when he suffered cardiac arrest, said Humboldt County Deputy Coroner Roy Horton.
A bear that was bedding just feet (meters) from the water source apparently saw or smelled the body and dragged Williams away, he said.
"The bear did eat most of this guy," he said. "He was about 85 percent consumed."
Friends became concerned about Williams on Oct. 11 and called the sheriff's department. They also visited his property and could smell the decaying body, Horton said.
Horton stressed that the bear was acting naturally after finding the man's lifeless body, and said black bears are normally timid and non-aggressive.
Wildlife officials in California report there has been no known fatal maulings by black bears.
(Reporting by Victoria Cavaliere in Seattle; Editing by Cynthia Johnston and Sandra Maler)