The disappearance of 70-year-old Patrick Moriarty from the tiny outback town of Larrimah is now considered suspicious, Northern Territory police say.
Emergency services have launched a second intense search in his hometown, about 500 kilometres south of Darwin.
Mr Moriarty and his dog Kellie haven’t been seen since December 16.
“The time frame for survival appears to have expired,” Detective Sergeant Matt Allen said.
“Detectives hold grave concerns for Paddy.”
Police and emergency services on Friday searched an 85-square-kilometre zone around Mr Moriarty’s home on the side of the Stuart Highway.
More than 20 officers and volunteers scoured the area by foot, dirt bike and helicopter.
The landscape and heat made search conditions challenging.
“Some of it is very difficult terrain to get through,” Sergeant Thomas Chalk said.
“There’s thick grass to get through and temperatures are extremely hot — about 40 degrees plus.”
There were no signs of a disturbance at Mr Moriarty’s property, and his car, quad bike and bank accounts are untouched.
“Unfortunately with the banks and hospitals and the national databases, we’ve got no signs of life,” Detective Sergeant Allen said.
“We’re never going to give up looking for Paddy.”
Locals say disappearance is strange
Larrimah has a population of 10 people including local publican Barry Sharpe, who is friends with Mr Moriarty.
“It’s strange Paddy and his dog are missing,” Mr Sharpe said.
“I think he’s been done in, I really do.”
Police are appealing for information and dashcam vision.
Authorities particularly want to talk to a group of tourists whose bus stopped at the pub on the night of his disappearance.
“If anyone has sighted Paddy, across the country, we want to hear from you,” Detective Sergeant Allen said.