Desert survival

H

Hoodoo

Joined
Aug 18, 1999
Messages
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It looks like a lot of people are interested in this so I thought it might be a good idea to start a thread devoted primarily to this topic.

I have almost zero experience in this other than, as a physiologist, I'm very familiar with research on desert animals and the physiological and behavioral mechanisms they employ for survival. This has some crossover into human physiology.

For instance, camels have a thick fur that insulates their body. This is essential because the ambient temperature exceeds body temperature, so the flow of heat is down the concentration gradient, from the ambient hotter air into the cooler body. Most of us experience just the opposite in nondesert environments. So if you are in the desert,this is an important reason to cover up during the heat of the day.

Another reason for thick fur on the camel is that it protects the evaporative surface of the skin. Sweat is used to cool the camel (and ourselves as well) by evaporative cooling. The idea is for the sweat to absorb heat from the body and carry it away by evaporation. However, if the evaporative surface is exposed to the sun, the sweat not only absorbs heat from the body, but also heat from the sun. This is a very inefficient use of sweat. It's better to protect the sweaty surface from the heat of the sun so that as much as possible, the only heat absorbed by the sweat comes from the body. You will save a lot of water this way. Thus, many desert dwellers are covered in loose fitting robes that 1)insulate the body from an influx of heat and 2) insulate the evaporative surface (the skin) from the sun.

One last interesting point is that camel hair is tipped in black. Black absorbs heat but the absorption occurs right at the surface so that it is trapped there and removed by convective winds. So desert dwellers often wear black outer robes instead of white, which they use instead as an under-robe.

The camel has many more adaptations for desert survival but these are the most applicable to our own survival.

Also, here are some desert survival links that might be worth checking out:
http://www.ci.phoenix.az.us/FIRE/desert.html http://www.etisurvival.com/des.htm http://www.ca.blm.gov/surprise/rttips.html http://www.desertusa.com/mag98/dec/stories/water.html http://www.desert-survivors.org/survival.html


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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
I hate the desert.... It's too damn hot
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Still I gotta do it. I'm running my annual 5 day desert survival program for the Navy and California Dept of Fish and Game in the California Desert this September. The information in your post is very accurate. More loose clothing improves survival times over bare skin. It seems counter intuitive but desert dwellers swear by loose clothing.

We will be augmenting with space blankets to turn the suns rays and doing most of the training at night.

ROn

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Learn Life Extension at:

http://www.survival.com ]
 
I think the clothing has to be loose to facilitate evaporation at the skin's surface. If the clothing is tight, it absorbs water and now the evaporative surface is at the outer edge of the clothing, not on the skin's surface. The clothing, then, acts to retard the influx of heat from the body into the sweat. In other words, it acts as an insulator between the body and the evaporative surface and evaporative cooling of the body is slowed as the flow of heat from the body into the sweat is slowed.

In the lab, I've heated mice up to the point where they begin to spread saliva on their body to cool evaporatively (they lack sweat glands). This is a last ditch effort at cooling because the matted fur acts as an insulator, as described above.

The camel's fur, in contrast, is very coarse. When camel's sweat, there is plenty of "room" for evaporation to occur, so the camel's fur does not become matted with sweat and the evaporative surface remains at the skin. And this is why loose clothing is more effective than tight clothing.

Have fun in the desert. Never spent time there myself but maybe someday I will.

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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
Hmmm,
I 've spent several years trecking in the desert environments of New Mexico and California. Usualy traveling with a friend or two, I've seen different people try different clothing solutions. My favorite (most comfortable for me, but maybe not the most conducive to long term survival)is,two layers of light weight, lightly colored cotton, and a full brimmed hat, with neck covering.
I have a friend who swears by wearing waffle type cotton long underwear under another layer of cotton. I tried it and felt like death was chasing across the sands.
To each their own.
 
some of the Bedouin tribes wear a black Burnoose or a loose robe. the air under the robe heats up and rises, creating a convection current that actualy cools you fairly well.

here in Las Vegas, i frequently wear a loose black t-shirt and keep it untucked... yeah i look like a slob, but if feels better than a tight or tucked in shirt, but i prefer to avoid direct sun in the middle of the day and the black clothes thing does not work if it does not get light on it to warm it.
 
Thanks for all the tips. I am backpacking in the Grand Canyon and other parts of Arizona later this month.
 
Originally posted by fixer:
some of the Bedouin tribes wear a black Burnoose or a loose robe. the air under the robe heats up and rises, creating a convection current that actualy cools you fairly well.
Click to expand...

That's pretty interesting. I know the Bedouin wear loose robes but I never thought about convective cooling occurring underneath. I wonder how extensive it is and the overall contribution to actual cooling? I would think it would be very limited. The magnitude of convective cooling is directly proportional to the square root of the velocity of the air movement. Thus a low velocity means low convective cooling and I imagine we are talking about fairly slow air movement under the robes. Nevertheless, I would guess that every little bit would help and convective cooling in general is an extremely effective mechanism of heat transfer (hence the use of fans).
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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom

[This message has been edited by Hoodoo (edited 07-31-2000).]
 
In the latest issue of the American Survival Guide there is a blurb on a book called "Desert Survival Skills" by David Alloway. Looks intersting. Anyone familiar with this book?


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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
I`m with Ron here.It is too hot.However,if you want to shoot Doves,you are going to be in someplace like El Centro. Get your limit and beat it for the river.Survival in each environment poses it`s problems. Artic is cold. Desert is hot.Jungle has lots of food and water.Also, Viet Cong and other unhealthy things.The shining mountains are the best.You can be comfortable there;if you are not tactical and not subject to light disipline.The Army can make any place bloody awfull.
 
Hoodoo, `fess up man, you're just trying to brush up to try to be on the next "Survivor" show in the Oz outback, aren't ya?

You can't fool us...
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Don LeHue

Rome did not create a great empire by having meetings...they did it by killing all those who opposed them.
 
Ya, you betcha. And I hope I get stranded on an island with an exotic dancer.
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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
Originally posted by FNG:
I`m with Ron here.It is too hot.However,if you want to shoot Doves,you are going to be in someplace like El Centro. Get your limit and beat it for the river.Survival in each environment poses it`s problems. Artic is cold. Desert is hot.Jungle has lots of food and water.Also, Viet Cong and other unhealthy things.The shining mountains are the best.You can be comfortable there;if you are not tactical and not subject to light disipline.The Army can make any place bloody awfull.
Click to expand...

Could you translate this for me?
confused.gif


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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
I guess one of the key factors in the thermodynamics of the desert is extreme sources of radiant heat. It is obvious that you want protection from the sun. The best protection from that is shade. Don't go wandering in the sun if you don't have to. Move at night or early or late in the day. Large loose hats like Mexican sombreros or asian farmer's hats are good, but may be a little hard to improvise. Consider using a parasol. If you support a sheet of newspaper, some cloth, or just a bunch of leaves on a light branch, you can make your own portable shade.

What may not be as obvious is the high amounts of radiant heat you get off the terrain around you. It is not unusual for desert surfaces to get over 150 degrees F. The surfaces will reflect some sunlight onto you plus they will radiate infrared light onto you as well. You not only want to get under shade, you also want to be on a north facing slope or other area where the ground around you is not as hot. This is where your loose fitting clothes pay extra dividends as they block the reflected and radiated heat from your body.

In regards to color, white has the best general reflective and radiative properties. White reflects incident light well yet also radiates infrared (your own heat radiation) well. I would expect black clothes to get you into trouble more than white clothes. Black clothes will absorb a lot more sunlight and reflected sunlight than white (there may not be much difference for long-wavelength infrared). Unless you have a very effective barrier between you and your black clothes I would expect you to receive more heat from black clothes than enhanced evaporative cooling could compensate for. I would expect even white clothes surfaces to heat up enough to help with convection. I wouldn't be looking for more.

I would favor very loose opaque white outer layers with lots of vents. A sheet or shirt hanging behind your hat to provide shade without obstructing air flow seems like a good idea. I also find a loose, light jacket (such as a windbreaker), with loose cuffless sleaves to be handy in hot or cold weather.

Again, Stay out of the Sun!!


[This message has been edited by Jeff Clark (edited 08-04-2000).]
 
Jeff, I think the critical point to your argument on clothing color is that the white clothes must be opaque. However, this is usually not the case. White clothing, plummage, fur etc, not only typically has high reflectivity but also high transmittance. In other words, more light will penetrate deeper with white clothing than with black clothing.

Let me give you a reverse example and talk about arctic adaptations. It has always been a curiosity that so many arctic animals were colored white. The standard thinking was that yes the animals are well camouflaged but thermally maladapted because black would be much better for absorbing thermal energy.

It turns out this is not the case. Studies have shown that birds with white pelage absorb more heat than birds with black plummage. And the key here is that this occurs only when the wind is blowing. When the air is still, the black bird absorbs more heat. The key here is transmittance. The black feathers trap heat at the surface and the heat then is removed more quickly when the wind blows. In contrast, although the white bird reflects more thermal energy, more energy penetrates more deeply, due to the high transmittance of the lighter colored feathers, and is more easily absorbed. Thus, during windchill conditions, the white bird stays warmer.

Another example is the white fur of the polar bear. Each white hair absorbs energy and transmits it to the skin in a way that is similar to a lucite fiber with high internal reflectiviy and thus high transmittance. At the level of the skin, the heat is rapidly absorbed because the skin is black.

I know all of this seems counterintuitive but it has been well documented in the scientific literature. And animals that live in the desert typically have hair that is tipped in black. The black tips absorb the heat, effectively trapping it at the surface of the pelage, where it can be removed by convective winds.

So I would argue, that in still air, white would be the choice as an outer garment and in moving air, black. But overall, black would be better because of the phenomenon of reverse wind chill. When the wind blows, since the ambient air is warmer than your body in the desert, it will heat you up, which is the opposite of wind chill. The convective flow of heat is into the body. So the most thermally stressful condition would be when the wind is blowing and a loose black outergarment would be more effective under this condition.



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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
Hoodoo I hope that I can translate. I`d be a poor leader if I couldn`t.
What do you not understand?
I thought that it was self explanatory. I guess not.
Doc Ron understood me fine.
What were we talking about? Oh, yes, survival.
It is neat to bring stuff with you.
It is not neat to need stuff that you have at home.
The "Shining Mountains" refer to the rockies.It`s an old term from the fur trappers.
OK, that may not be well known.
Chances are, you will have what`s in your pockets in in inadvertant survival situation.Check NTSB.gov.They are the experts.
Solar stills do not work.
A load bearing vest is not a bad idea. If you live in a Commie state, it will also hide your 1911 nicely.
If you have never been dove shooting, I don`t know what to tell you there.Go do it!Bring lots of ammo. They are not easy to hit.
Living in the field is not as much fun in the Army as it is in the boy scouts.You don`t get camp fire.
The Colorado R. is near where we shoot doves;thus; head for the river for relief from the heat.Get wet.
You won`t have to worry about Charlie.
If you are in Alaska, you are not too interested in desert survival. How do I pack an Akio,would come to mind.
These guys are good at what they do.Jeff, Ron and others.You need to define where it is that your going to do it.
I went through the service schools,same as everybody else.
I have a JWTC patch. Artic and other survival schools did not give you anything special.
Did I miss anything?
I mean to be esoteric, but not to that extent.


 
FNG,
I think I see what you are saying. Your posts are more like poetry than prose.



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Hoodoo

And so, to all outdoor folks, the knife is the most important item of equipment.

Ellsworth Jaeger - Wildwood Wisdom
 
Since cloth can be much denser than loose fir it can be much more opaque than fir. Since loose fir is rare in modern attire the animal model only loosely correlates to the human model for desert attire. In Saudi Arabia the traditional garment, the thobe, is usually white in warm or hot weather (according to their government website).
 
When I lived in Utah/Arizona/New Mexico I tried the dark vs. light clothing concept. I agree with the Mexicans that light colored and loose is best for the Americas. Cover all skin. Dark just seems to get hotter than Hades, especially for a hat. I'm aware that in Arabia black is preferred, but it doesn't work for me.
 
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