308 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1940 



other things to fill portions of the crevices or to build a mound at 

 the base of the cliff in order that it may make its nest under a 

 protective covering. It is remarkable how many of the exceedingly 

 spiny dried prickly pear joints they will use when such material is 

 available. Often the nest is composed chiefly of these joints, which 

 are indeed excellent protection against enemies. Certainly we can- 

 not doubt that the pack rat is well aware of their value. With regard 

 to the pack rats' propensity for carrying a shining object away from 

 a camp and leaving something in its place, it is my theory that the 

 animals are usually carrying something, and that when they find 

 the bright object that they prefer they drop the one they have been 

 carrying and pick up the one that is more to their liking. 



In building their dams or their houses, beavers have need to use 

 considerable earth that sometimes must be transported over dis- 

 tances of several feet or even rods. One method of carrying it is 

 to gather a mass in their hands held against their breasts while they 

 walk or swim to the place where the earth is needed. In this man- 

 ner they move a surprising amount of earth. In addition to earth, 

 sticks and occasionally stones are regularly used by beavers in the 

 building of dams. 



Wasps and ants have been observed picking up small pebbles m 

 their jaws and using them to tamp the earth. Wasps have been ob- 

 served to take a small twig and sweep or smooth the ground over 

 their burrow which they had just filled. These are a few known 

 instances of the use of tools by some of the lower animals. 



Occasionally individual monkeys adopt the practice of throwing 

 objects at a fancied enemy. However, this is not a general practice 

 among monkeys despite the popular belief to the contra r3^ The 

 practice of natives of southern Asia and the East Indies of sending 

 monkeys up coconut trees to break off the nuts is often cited as 

 evidence that monkeys do throw objects at adversaries. In reality 

 the monkeys, usually pig-tailed macaques {Macaca nemestrina) ^ are 

 carefully trained to go up coconut trees, twist off the ripe coconuts 

 by twirling them between their hind feet, and let them fall on the 

 ground. 



I once saw an orangutan grasp a handful of more or less parallel 

 straws in both hands, held about 20 inches apart. The animal then 

 looped his rude straw rope over a projecting iron pipe and swung 



^^^ ^*- EFFICIENCY 



Modern mankind lays stress on skill and efficiency. Evidently 

 animals do likewise, for careful observation of the ways in which 

 they carry out the everyday practices of their lives indicates that 

 they are surprisingly efficient in all their actions. Perhaj)s if it were 



