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Show 488 TECHNICAL BULLETIN NO. 107 WATER REQUIREMENTS OF DESERT ANIMALS The junk-heap nest | s of wood rat s (Neotoma) are 2 common h'l Ikangaroo rat (Dipodomys) and pock et mouse (Perognathus)wb1:r? bOWS are abundant. These little crea tures are tied to their home hlglré‘otuors and caclfinot tgavel even 4 or 5 miles to and from a water . , say no mg 0 a 40- or 50-mile rou nd tri Such ' mifglhliswork oi": more water than the creature could drink a jaunt curios1 y 18 arou _ sed , and the observer be gins ' to thin : k 1tam: ptrillblem. The animal has to hav e water for its life proceggeesr T1111 1 asnt any. A paradoxical situation. What is the answer", e "number of inquiries we have had, not only from the la. pull-3111c but: from sc1entists, proves the interest y u is 1 important? It may be a trifl e difficult t ' Eggfiiittl'on getwein Sthe answer to this problem andszepiaitligglc ion . ereo . cientifically, it is no less im orta t th Ether biological problem in the rea lm of pure sgienc: Witeiniz n . O livingncleflellssalbd necessiilry1 major component (by weight) of all _ , an as suc as been investigated from ever vi pglllnt by both - plant and animal physiologists. Its relatiorfship VtVo ac 1V1 y and life has been long and painstakingly studied and e - coai‘ilnuis to lie investigated, and rightly so. e p ysio ogical. necessities of the tiss ues of desert an ' :0 water are essentially the same as those of animals of 1:13:12: tfigiggslggfi the ILrequlilrefiients of the animal as an organic unit and ons y w ic it meet th been thoroughly investigated. 5 ' ose requirements have not yet tion. Ther' e is no bibliograph y, referenc es are undated, and auth tag: fiifltganfliby tsurglanréleslpnly, mak ing it practically impossible: _ . ex en an c aracter of the obser ' imsents, if 38920? which statements are based vatlons, or exper- umner 5 enumerated Some Biolo gzca ' . l Problems Southwestern Deserts. Qne of his most important suggeijtiooiisr evendyet not adequately investigated , is that of emphasizing the dleiseee t of expeilumental studies upon the special physiology of r mamma s, on a scale com arab l ' ' been conducted on desert plants."p e Wlth those WhICh have ,Shreve (1934), in Problems of the Desert, said: Relat ively little has been done . . on th ' of anim al . ' - 22:31:28? 1the trole of water in meta e water relations bolism in the animal grOprsAofCOtrlIile 0 ye pOSSible. The loss and requirem ent have been investigated Kashkarov (1935) says: 489 . The ultimate aim of scientific study of a desert led on by zoologists and other specialists is to come into full possession of it, that is to promote cultivation, animal husbandry and instalment of a settled population. Desert life conditions must be described and understood for that purpose. The zooecologist must give a description of life conditions in terms of the life process itself. Such an aim led Kashkarov to a study related in Ecology of Domestic Animals (19-) ,1 from which investigation he concluded as follows concerning Karakul sheep: The lambs of the Karakul sheep grow and develop quicker than those of the European sheep . . . [owing to] the shortness of the vegetative period. . . . The fat tail is a reserve of nutritive substance and of metabolic water, and enables the Karakul sheep to live through the winter and to survive the summer drought. This means that the Karakul sheep is a desert-adapted domestic animal. It might be worth while to try this breed in the Southwest. Howell and Gersh (1935) carried out some controlled physiological experiments on Dipodomys which will be referred to in our discussion of that genus. Further experimentation of this character should be done with pocket mice (Perognathus). , The Carnegie Institution Desert Laboratory, at Tucson, was concerned for many years with the water relations of desert plants. It behooves zoologists to learn something of the same sort with respect to animals. It was with this thought in mind and with the object of investigating the water relationships of desert animals that we undertook some years ago a long-time project for the study of this problem. Our field investigations on mammals (Vorhies and Taylor, 1922, 1933, 1940) offered so much opportunity for general observations and 'thought on the problem as to foster a desire to undertake field studies rather than laboratory experiments in physiology. Aptitude, training, and the opportunities at hand determined this choice, rather than any failure to recognize the importance of physiological investigations. The objective of the field investigations was to secure records of the "micro-climates" of certain key species of small mammals of the arid Southwest. We shall have to assume herein that the general characteristics of a desert climate, such as low relative humidity, scanty precipitation, much sunshine and heat, and a wide daily range of temperature and humidity are known to the reader.2 The climate of Tucson, Arizona, and the surrounding valley area in which the field records were made is essentially a desert climate, and is typical of a large area of the southwestern United States and northwestern Mexico. It is not of the extreme desert type, and is commonly referred to as "semiarid." Toward Yuma, in the southwestern corner of Arizona, the altitude decreases, the 1Reprint, in author's library, without date or indication publication. 2Buxton (1923) has a good chapter on the desert climate. of original |
