278 ANNUAL REPORT SAHTHSONIAN INSTITUTION, 19 40 



roundings so well that their coloration is their chief protection. 

 Extreme alertness and the ability to slip away quietly and unob- 

 trusively at the first sign of danger are common and effective safety 

 devices. 



OBTAINING FOOD 



Since all individuals of all kinds of animals must obtain their 

 food under the conditions peculiar to their respective ranges, there 

 is an almost infinite variety in the methods of animal food-getting. 

 Each of these methods, of course, is well adapted to the physique and 

 mentality of the animal and to the conditions under which the food 

 must be obtained. Some animals live only from meal to meal, 

 others hoard food for periods of scarcity, and still others arrange to 

 avoid eating during periods when food will not be available. Some 

 animals must make radical seasonal changes in their diets to be 

 able to survive. 



Animals that live in the midst of a food supply that is generally 

 plentiful, as for example horses (Equus), cattle (Bos), sheep (Ovis), 

 rabbits, and many others, merely have to look about them and select 

 the kind of food they prefer. Sloths {Brady pus and Choloepus) 

 feed almost entirely on leaves, and, since these mammals live only 

 in the Tropics where the trees are green throughout the year, their 

 problem of obtaining food is very simple. They merely climb a tree 

 that produces the kind of leaves they like and remain there in- 

 definitely. In some cases at least, sloths appear to live practically 

 their entire lives in a single tree. 



Porcupines, in the northern portion of North America, have 

 almost as simple a food problem as the tropical sloths. Although, 

 unlike a sloth, a porcupine is quite capable of traveling on the ground, 

 one of these prickly rodents may take up its abode in an ever- 

 green tree that has bark to its liking and remain there during an 

 entire winter, or at least until it has eaten practically all the bark 

 from the small twigs and branches. 



Other creatures must hunt for and capture their prey or must 

 search industriously for tiny particles of an inadequate food supply. 

 A good example of the latter problem is the struggle for existence 

 by the tiny pocket mice. The homes of these small rodents are 

 simple burrows in the barren sandy or rocky deserts of the south- 

 western United States. The burrows may be from a few inches 

 to 2 or 3 feet in length with from one to three chambers at the end. 

 One of these chambers is the storehouse. The animals usually go 

 out early in the evening and industriously search for every seed they 

 can find. Tliese they put into their fur-lined cheek pouches. When 

 they have obtained a load of seeds they return to the burrow and 

 deposit their valuables in the storehouse. Thus they make trip 



