ANIMAL BEHAVIOR^ — WALKER 311 



In the zoo, we place either the inclined disk-type or the ferris-type 

 exercise wheels in cages of many of the smaller animals so that they 

 may have an opportunity to exercise. Many of the more active 

 animals use these wheels and plainly enjoy them. Some of our 

 keepers have observed that when small exercise wheels have been 

 standing where the wild house mice could get at them they would 

 run the wheels even though they were entirely free to come and go 

 about the premises as they pleased. 



A little pocket mouse now living in my study at home runs her 

 wheel almost continuously from about 9 p. m. to 7 a. m. "Ony," the 

 grasshopper mouse that also lives in my study, does not run his wheel 

 so constantly, but he uses it at frequent intervals from about 10 p. m. 

 to 6 a. m. Each wheel has a characteristic sound that I can hear in 

 my bedroom ; thus I am kept well informed of my pets' activities. 



Vernon Bailey, for many years Chief Field Naturalist of the 

 United States Biological Survey, has informed me that he has found 

 that some of the animals in the wild state, particularly kangaroo rats, 

 would run disk-type wheels placed near their burrows. 



CONCLUSION 



All persons who have kept pets have probably bored their friends 

 by telling them of the interesting and clever behavior of these 

 animals, and no doubt most people have thought that their pets were 

 behaving in an unusual manner and that they were exceptions to the 

 rule. This is undoubtedly true in some cases where the pets have 

 had exceptional educational advantages in homes where they were 

 treated almost as one of the family ; but we should bear in mind that 

 animals' reactions to the new conditions with which they may be 

 surrounded are the product of the age-long efforts of the species to 

 adapt itself to its surroundings, and that the individual confronted 

 with new conditions must meet those conditions to the best of his 

 ability based on the instincts of the species and his own intelligence. 



Almost every dog owner has seen his pet do many things that seem 

 to him to indicate unusual intelligence on the animal's part. Gen- 

 erally the acts that he has observed do show intelligence, but they are 

 not isolated instances. They are merely isolated cases of a man's 

 observing and in part comprehending some of the things that animals 

 can regularly do. 



Any species of mammal, bird, reptile, amphibian, fish, insect, or 

 other form of animal life that has survived the vicissitudes of the 

 ages has developed technique that is well adapted to the perpetuation 

 of the species. But the student will regularly encounter actions that 

 he is unable to explain. He may, however, feel certain that such 

 actions are not haphazard but that they are very definitely associated 



