The disappearance of four-year-old August ‘Gus’ Lamont has devastated a remote South Australian community and captured national attention — but nearly six weeks on, there’s still no sign of the little blond boy.

Gus was last seen around 5pm on September 27, playing outside the Oak Park homestead while his grandmother cared for his younger brother Ronnie inside.

His mother and grandfather were out tending sheep on the family’s 6,000-hectare property, 43km south of Yunta.

The terrain is brutal — arid, rocky,vast and unforgiving to most living creatures.

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.

Gus has long curly blond 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.

The only clue uncovered so far is a single footprint found on September 30 — roughly 500m from where Gus was last seen.

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.

South Australian Police Assistant Commissioner Ian Parrott said the family had been spoken about the likelihood Gus wouldn’t be found alive.

“Senior police spoke to Gus’ family and prepared them for the fact that Gus may not have survived due to the passage of time, his age and the nature of the terrain he is missing in,” he said in early October.

“While those involved in the search have been hoping for a miracle, over the past 48 hours, the search has shifted to a recovery operation.”

Gus’s case has since been handed to the missing persons section of the Major Crime Investigation Branch.

Last week, police and SES volunteers drained 3.2 million litres of water from a dam just 600m from the homestead to rule out that Gus may have drowned. His body was not located in the water.

Police Commissioner Stevens on Wednesday reaffirmed the force’s commitment to finding Gus with a pending fourth search to happen in the near future.

“We will be going back to the property to conduct further searches based on further analysis of data and further advice,” he said.

SOURCE: https://7news.com.au/news/gus-lamont-search-expert-outlines-survival-odds-as-local-volunteer-says-case-defies-logic-c-20607103