Exactly a month to the day since little Gus Lamont vanished from his family’s remote sheep station, new theories have emerged about just how far he might have gone.

The four-year-old was last seen around 5pm on Saturday, September 27, playing on a mound of dirt near the homestead — about 40km south of Yunta in South Australia’s Mid North.

When his grandmother called him in just 30 minutes later, he was gone, according to his family.

What followed was one of the largest search operations in South Australian history. Police, SES volunteers and the Australian Army scoured more than 60,000 hectares of harsh terrain by air and ground.

A second week-long search earlier this month at the family property failed to find any new clues.

The only clue that remains is a single footprint found on September 30, just 500 metres from where Gus was last seen.

The search is that of recovery, with experts telling police that due to the harsh climate that Gus is unlikely to be found alive.

Police and volunteers have covered a six-kilometre radius from the homestead, but an expert now believe Gus may have ventured well beyond the area that’s been extensively searched.

Nina Siversten, an expert in human physiology from Flinders University, said Gus could’ve travelled outside the search zone.

“Over a three-day period we’re looking at potentially three to eight kilometres,” she told 7NEWS exclusively.

Gus has long curly blonde hair and was wearing a blue long-sleeved Minions T-shirt, a grey sun hat and boots when he went missing. While it’s hoped the hat or shirt may have been discarded if he was lost and possibly dehydrated, Siversten says it’s more likely he would keep them on.

“If you are in really cold conditions and frozen then your instinct would actually be to undress,” she said.

Police have been working on one theory — that he simply wandered off. But with no access to water, food or shelter, survival is considered unlikely.

“If the child could access some sort of moisture or dew or moist leaves that could increase it somewhat beyond the three days,” Siversten said.

“I think that fear would be an absolute factor and that would impact on the ability to move and ability but also on finding shelter.”

Former SES volunteer Jason O’Connell, who walked the property alongside Gus’s father, said the case defies logic.

“My heart breaks for (the father),” O’Connell told 7NEWS.

“It’s been searched. (Gus) is not there.”

O’Connell was given police approval to use his tracking skills to help with the search

“I just don’t get how (Gus) vanished like that,” O’Connell said.

Police have said there is no evidence at this stage to suggest any foul play, with Gus’s mother and a grandparent tending the station’s flock, while Gus was with his grandmother and younger brother Ronnie at the time.

Reportedly, Gus’s father lives off the property.

They’re now in the final stages of assessing hours’ worth of drone vision taken of the property — using infrared technology to pick up any clues. At this point, there are no further searches planned, but detectives haven’t ruled out returning.

“There is still work that is ongoing by SA Police. They are continuing to make inquiries. There are a few different sources of thinking but I’m not in a position to comment on it beyond that,” SA Premier Peter Malinauskas said.

Anyone with information is urged to contact police.

SOURCE: https://7news.com.au/news/new-expert-theory-suggests-missing-gus-lamont-may-be-outside-the-search-zone-c-20484471