304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1940 



Some monkeys have even gone farther and supplemented their 

 grooming with a very definite system of hair plucking. This habit is 

 especially well developed in the Japanese macaque. In this animal 

 the hair grows fairly long on the sides of the head as well as on the 

 crown. Some individuals have developed a system of plucking the 

 hair around the sides of their companions' heads so as to give almost 

 the effect of a human hair cut. The hair on the crown is left un- 

 disturbed. This plucking is not a hit-and-miss affair, it is very sys- 

 tematic and symmetrical, giving the animals the appearance of hav- 

 ing been carefuly groomed. (See pi. 15, fig 1.) One individual that I 

 have observed, that lives alone, plucks the hair on his own forearm. 



There are members of our medical profession and many other in- 

 dividuals who feel that the human body derives a very definite bene- 

 fit from close contact with the earth. By the nature of their lives, 

 animals are more constantly in contact with the earth than are human 

 beings. When we observe the true enjoyment that pigs, rhinocer- 

 oses, elephants, and numerous other animals derive from wallowing in 

 the mud, can we doubt that they get some very definite benefit from 

 this habit ? The skins of wallowing mammals being practically bare 

 are especially subject to drying and to the bites of insects. Tliere- 

 fore, mud baths must be soothing if nothing more. 



Many birds will bathe whenever water is available even though 

 it be ice cold. Following such a bath, they have a bedraggled ap- 

 pearance but if one will observe them, he will see that they vigorously 

 shake their plumage and preen it until the feathers are fluffed out 

 and in good condition. Indeed, in many instances, if birds cannot 

 bathe, their plumage becomes unsightly and they themselves appear 

 to become discontented and uncomfortable. Birds also shake them- 

 selves and fluff out and arrange their feathers. Chickens dusting in 

 the road or elsewhere, then shaking their feathers and cleaning them, 

 are familiar examples of this habit. Even flies and other insects 

 groom themselves after having eaten or having become soiled. In- 

 numerable other instances might be mentioned. 



MEMORY 



Memory is a faculty that we ascribe mainly to human beings; but 

 most animals obviously remember things that concern them. Natur- 

 ally the things that make the greatest impression on animals are 

 those that relate to avoidance of their enemies, the finding of their 

 home and food, and other activities essential to their welfare. The 

 term "homing instinct" has been applied to the pronounced ability 

 of certain animals, noticeably cats and carrier pigeons, to find their 

 way back to their homes. However, it is even more pronounced in 

 the birds that migrate many hundreds of miles and find their way 



