DOMESTICATED ANIMALS INHABITING DESERT AREAS 



Dr Norman C. Wright 

 {Scientific Adviser to the Ministry of Food, London) 



I do not think I need apologise for limiting my paper to domesticated animals, 

 for such animals are essential to the economy of the human populations inhabiting 

 desert areas; they provide milk (often the only form of liquid available for human 

 consumption) ghee and cheese, meat, hides and skins for clothing, hair for tents and 

 other purposes, means of human and baggage transport, and even fuel in the form of 

 dried dung. These products are provided not only in sufficient quantity to meet the 

 local population's own needs, but are frequently available for export from the desert 

 areas. In spite of this, textbooks on animal ecology have almost without exception 

 failed to devote more than an occasional paragraph or two to domesticated anim.als, 

 and particularly to those inhabiting desert areas, while little work has been done on 

 the physiological reactions of such animals to their environments. This applies 

 equally to practically all classes of desert stock, — not merely to camels but to fat- 

 tailed and fat-rumped sheep, goats, yaks and donkeys. Our largest body of know- 

 ledge is in fact on cattle, which are not typical desert animals, though they are of 

 course widely found in the semi- arid areas bordering on deserts, such as East and 

 Central Africa and Northern India. For this reason I have not hesitated to draw on 

 cattle for certain illustrative material in this paper. 



The effects of climate on the morphology of desert animals may be roughly 

 classed as direct and indirect. The direct effects are associated with environmen- 

 tal temperature (including solar radiation), with humidity, and with air movement. 

 These can affect body size and conformation, the skin structure and nature of the 

 coat covering, and possibly certain other properties (such as the subcutaneous fat 

 layer) which may affect the absorption or dissipation of heat. The indirect effects 

 are associated with the environmental vegetation and water supplies, and hence with 

 the nutrition of the animal. These may to some extent affect size ; they may affect 

 conformation in so far as this is influenced by the local deposition of nutrient re- 

 serves designed to tide over rainless periods; they may affect the mechanism of 

 food intake, and of water intake and conservation ; and they may be related to the 

 animal's facility for speed of movement. 



It will therefore be desirable to summarise briefly the climatic environments to 

 which domesticated desert animals need to be adapted. Since such animals are too 

 large to avoid the extremes of climate in ways which are possible for smaller mam- 

 mals (e.g. by burrowing) it is necessary to take into account the full climatic en- 

 vironment of the open desert. For this purpose ordinary routine meteorological data, 

 however inadequate, is the only source to draw on. 



In sub- tropical and tropical deserts (such as the Sahara) the outstanding fea- 

 ture is the uniformly high temperature. As one goes north-east across the Great 

 Palaearctic Desert region these consistently high temperatures are no longer found, 

 but they are replaced by two characteristics, — by extreme seasonal variations and 

 (particularly in the mid- regions at lower altitudes such as the Iraqi Desert) by 



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