The manhunt continues for Brian Laundrie, who will face serious charges once apprehended by law enforcement.

He has now been missing for a month, with investigators following multiple leads in an effort to track him down.

If he is relying upon his survival skills to remain outdoors and away from other humans, how long could that last?

True expert survivalists are weighing in ... and explaining that there's a decent chance that Brian could already be dead somewhere.

If one believes the sometimes contradictory stories told by Brian Laundrie's parents, he was last seen at a nature reserve near their home.

The 23-year-old was traveling and spending a lot of time in the woods with his late fiancee, Gabby Petito, before her murder.

It has been assumed by many, both in and out of law enforcement, that he is relying upon these same skills to attempt to evade authorities.

Those of us who are what one might call "indoorsy" naturally wonder how long this is viable for Brian.

Could a 23-year-old who previously lived in a van simply forge a new life for himself in the wilderness and never be seen again?

There are actual experts about survival in the wilderness, and they say that it's not likely that Brian could make it that way.

Jason Marsteiner is the founder and lead instructor of Colorado Mountain Man Survival, and spoke to Insider about Brian's chances.

According to him, people who are stranded away from civilization "break down within five or six days."

Brian vanished a month ago.

"Especially if they don't have food," Marsteiner continued.

He explained that "you're not eating what your body needs."

And not having food leads to disaster.

"You're either going to get angry," Marsteiner said.

"Or you are going to have some sort of emotional distress," he continued.

Either way, Marsteiner explained, "that makes you make poor decisions."

"Plus, he's got this stress of the situation," Marsteiner said of Brian Laundrie specifically.

That stresser is "why he's being pursued to begin with."

Though Brian's initial federal arrest warrant is over misuse of Gabby's bank card, more charges are very likely.

Robert Urban is the founder and chief instructor of the Urban Survival Academy in Florida.

Also speaking to Insider, he echoed the sentiment that Brian's mental state is likely even worse now than it was during and after Gabby's murder.

Most people who are having to survive in the woods hope to hear rescue helicopters. Brian holds no such hope.

"Survival is based on the hope that I'm going to get rescued," Urban observed.

"When I do, my life's going to be better, and I'll be back with my friends and family and get back to normal," he characterized that thinking.

Urban added: "So there's a big positive mental attitude, even for experienced guys like myself."

"And the only way that you really have that mental fortitude is if there's that hope of it," Urban continued.

"So in this specific scenario of if this guy gets rescued -- 'rescued' -- his life is not going to be better than it was in the past," Urban explained.

Being lost in the woods is very different from deliberately making yourself lost in order to hide ... but both can be deadly.

Whether Brian is in the Carlton Reserve or somewhere similar, both Marsteiner and Urban have doubts that he could survive for long.

His sister recently called Brian a "mediocre survivalist."

It sounds like the survival experts agree that he's not going to Swiss Family Robinson himself a hideaway to go unseen for months on end.

Marsteiner noted that even those with genuine training in survival struggle "to survive for seven days."

"For Laundrie, with a minimal amount of gear, it's going to be quite difficult," he continued.

Marsteiner added: "Surviving is not something that you're going to pick up quickly."

After all, there is more to it than not having access to edible food and water.

Mosquitos are a nuisance for people living in houses. They can be a genuine danger to someone who is living outside.

In the wilderness in Florida, Brian also risks encounters with bears, wild hogs, snakes, coyotes, and alligators.

When he does look for food, foraging has its own risks.

A lot of "food" found in the woods is inedbile for humans.

Some is just difficult to digest. Other things are poisonous, or contaminated.

Normally, Marsteiner explained, he would expect someone camping out on a nature reserve to resupply from other visitors.

However, the Carlton reserve has been closed to the public since September 21.

Even with portable water filtration devices, Urban predicted that Brian could struggle to find safely drinkable water.

Starting fires without being noticed could also be a struggle," Marsteiner added.

There is a chance that Brian is elsewhere, and that he could easily scavenge off of unsuspecting campers.

Missing food from a campsite could be blamed on wild animals or even forgetfulness. Who would think that it's America's most wanted fugitive?

There is also a real chance, both survival experts agree, that Brian could have already died.

Even if he was determined to live, there are all of the aforementioned dangers.

If he did die, scavengers in the intense Florida heat this time of year could make short work of his remains.

Urban suggested that the most likely scenario is that Brian Laundrie is simply not on the Carlton reserve.

He also listed the very real possibility that someone is helping him, supplying him with food or other necessities.

If so, it's probably not an obvious suspect -- his closest associates are likely under surveillance.

The third option, Urban noted, is that Brian -- by his own hand or otherwise -- is already dead.

It does seem likely that the volume of unwavering media attention that Gabby Petito's disappearance and murder has received will lead to him being found.

We hope that Gabby's loved ones are able to get answers, closure, and justice.