378 THE FUTURE OF ARID LANDS 
3. The camel (and the donkey) maintains its appetite in spite 
of dehydration. While other animals will lose their appetites when 
deprived of drinking water, the camel continues to eat until the 
water depletion becomes severe. 
The value of maintaining the appetite will be clear when one 
considers that tolerance to water deprivation permits the animal 
to graze over a large area, and continued food intake is the 
essential to the utilization of the available grazing. 
The effect of the range of the animal on the area available for 
grazing is illustrated by the diagram in Figure 2. The areas that 
can be covered by different animals are encircled, using as radii 
the number of days the animals can go without water in the 
severe desert summer (Sahara). (The figure for sheep is only an 
estimate because we lack sufficient data.) In reality, the animals 
do not remain away from water until the limit of endurance. In 
the western parts of the Grand Erg Occidental of the Sahara, the 
sheep are returned to the wells for watering every day in the 
summer. The camels stay away for several days but will return on 
their own initiative within four days. This is in the same propor- 
tion as the maximal endurances, as indicated in the diagram by 
the numbers on the radii. 
(The actual areas covered may be even more to the advantage 
of the camel because of the much greater speed of this animal.) 
I would like to discuss separately the meaning of this diagram 
to maintenance and to production. 
In summer, vegetation and water supply are at a minimum, 
and an important problem is to maintain an animal stock suffi- 
ciently large so that later the winter grazing can be efficiently 
utilized. In this case the problem is one of maintenance rather 
than production. Assuming that the vegetation density is unt- 
form over the areas represented in the diagram, one can calculate 
the approximate relative numbers of animals that can be main- 
tained, and likewise, as given in the diagram, the total weight of 
meat maintained. 
When the time of abundant feed comes, production is resumed. 
At this time one might prefer a rapidly reproducing and growing 
animal in order to utilize maximally the food available. However, 
this reasoning is fallacious. It is true that production is more 
