A man who died outside his rural Northern California home had his corpse dragged away and eaten by a black bear that was sheltering nearby.

The 65-year-old man, identified as Marion Williams, had walked from his trailer in Humboldt County to a water source about 100 metres away when he suffered cardiac arrest and died, Humboldt County deputy coroner Roy Horton said.

A bear that was bedding just metres from the water source apparently saw or smelt the body and dragged Mr Williams away, he said on Friday.

"The bear saw the opportunity for a food source and took advantage of it," he said.

He said the bear stripped Mr Williams out of his clothes and necklace and fed on him for several days.

"The bear did eat most of this guy," he said.

"He was about 85 per cent consumed."

Friends became concerned about Mr Williams days after the incident and called the sheriff's department.

They also visited his property and could smell the decaying body.

Mr 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 have been no known fatal maulings by black bears.

Reuters