Volume , Issue

“Creatures that by a rule in nature teach the act of order to a peopled kingdom”

                                                 -William Shakespeare, Henry V

While Shakespeare was referring to the honeybee, desert creatures also teach us how to live and survive in the desert. In the last columnhttps://wms.org/magazine/1195/plants-of-the-desert we learned how plants have made evolutionary adaptions to thrive in arid conditions. Desert animals have also prospered in extreme temperature variations and lack of water.
The basic rule of water discipline in hot climates has always been “conserve your sweat, not your water” (or no one should ever die of thirst with water in his canteen). This begs the question: how do you conserve your sweat? Observing how desert animals have adapted gives us some clues. Knowing that we cannot violate the Laws of Thermodynamics, sometimes we must alter our behavior and maximize our physiology in order to survive in a hot environment. Humans , like many other mammals, use evaporation as a primary method of cooling when the ambient temperature is greater than 95 degree F , which is skin temperature and doesn’t allow for heat loss via radiation. In other words, because of the 2Nd Law, we take on heat from the environment when the ambient temperature is greater than 95 degrees F. Rate of evaporation of sweat depends on surface area and body size. The higher the surface area to volume, the more evaporation that occurs, there fore a smaller mammal such as a kangaroo rat or mouse is at a greater disadvantage than say a horse or camel.

The smaller animal cannot travel as far as the larger to find water either, but a smaller animal can take advantage of microclimates such as underground burrows and plant habitats. Larger animals have a larger capacity for rehydration when water is available and can tolerate greater increases in body temperature. Other physiologic adaptations include decreasing fecal water content, increasing urine concentration and osmolality , extracting water from plant material, and in some cases (e.g. camel), thick fur. So how can we benefit from what desert animals do to survive in hot dry climates?
While it would be impossible for a human to develop the physiology of a kangaroo rat, we can maximize our own physiology to acclimatize before going into the desert. Accli ma tization may take several days and it involves gradual increase in exertion in a hot ambient environment. This may be the actual ecosystem or it can be done in a sauna (acclimation). What this does is: 1) it recruits more sweat glands that have become dormant in our climate conditioned world; 2) i t allows our bodies to conserve sodium and potassium in our sweat content, decreasing the risk for electrolyte problems; 3) it allows us to begin sweating at a lower body temperature; and 4) it increases blood flow to the skin. All of these adaptations increase our ability to respond to hot conditions.

Figure 1: Temperature variations based on distance from ground surface.

In addition to our physiology, we can affect our behavior also to adapt. We know that in the desert environment the highest temperature is at ground level. Camels may be several feet above the ground and mice several feet below the ground; each is trying to find a cool place (Figure 1). Just moving into the shade can decrease the ambient temperature by 20 degrees (Figure 2). Most desert animals try to be inactive during the hottest parts of the day, say from 11 AM-2 PM.

Figure 2: Shade shelter in the Grand Canyon. There is a 20-degree difference between sun and shade.

The desert traveler should conserve his/her sweat by:

1)Acclimatizing prior to visiting the desert

2) Decreasing activity during the hottest part of the day

3) Getting off the surface of the ground by going above the ground or below the ground

4) Staying in the shade as much as possible

5) Keeping as much of the skin covered as possible

The deserts of the world are amazing and beautiful places. We can enjoy them more if we emulate the “creatures that by a rule in nature teach.”

You Might Also Be Interested in

Desert: Let's Go Out to the Movies

Edward J. (Mel) Otten, MD, FACMT, FAWM12/15/2017

Resident desert expert Edward "Mel" Otten brings us his top 10 desert movies...

Desert: Conserve Sweat, Not Water

Edward J. (Mel) Otten, MD, FACMT, FAWM2/6/2017

The basic rule of water discipline...has always been “conserve your sweat, not your water”...

Desert: Plants of the Desert

Edward J. (Mel) Otten, MD, FACMT, FAWM11/11/2016

I have always been interested in desert plants...

Books of the Desert

Edward J. (Mel) Otten, MD, FACMT, FAWM6/23/2016

A starter guide on books to get you into the desert...