314 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



(Some caretakers maintain that certain parrots do better in small 

 cages than in large ones.) If it is a climbing animal, trees, horizontal 

 bars, swings, ropes, rings, and poles will all stimulate activity. 

 Wooden or rubber balls, or other toys, even dolls, are sometimes useful, 

 either as playthings or as companions. Wlieels that will give the 

 animal a sense of progress are particularly good. They may be of 

 the inclined disk type, or of the ferris wheel type. (See pi. 1.) It is 

 also probable that successful exercising devices might be developed 

 for the small cats, or other animals of similar size, after the model 

 of the endless-belt treadmills, such as were at one time made to utilize 

 dog and horse power for man's purposes. 



Some animals that do not thrive in captivity when kept alone do 

 very well in groups with others of their kind. An excellent example 

 of this is the ani; lone individuals promptly die in captivity, but 

 groups of four to six have lived for several years in the National 

 Zoological Park under exactly the same treatment as previously given 

 single birds. Others thrive when a companion of another kind is with 

 them, if one of their own kind is not available. There have been 

 numerous odd companionships of this kind, such as the friendship 

 between an African rhinoceros and a goat. We have in the Zoo a 

 Javan macaque monkey that lovingly fondles its pet guinea pig, and 

 IS thus provided with an interest in life. One black-tailed marmoset 

 in a cage by itself at the National Zoological Park was gradually 

 failing. Presently two other marmosets of a different species were 

 put in the cage with it. At first, it was very much afraid of them 

 and stayed as far away as possible. After a few days, it gained a 

 little courage and would occasionally come near the others, and finally 

 it was participating in their play. Thus, the lethargy and so-called 

 cage paralysis which had been coming on was averted. This example 

 rather definitely suggests that one type of cage paralysis is the result 

 of a wasting away of muscles due to inactivity, which can be prevented 

 by providing animals with a good-sized cage and inducement to 

 exercise. 



When placing animals of the same kind or different kinds together, 

 care must be taken to prevent fighting. It is a good plan to keep 

 them in adjacent cages so they may see and smell each other for a 

 few hours, days, or even weeks, and thus become acquainted. Wlien 

 they are first put together, it should be done very quietly and the 

 animals should be allowed to make their own approach to each other. 

 Careful watch should be kept until it is seen whether or not they 

 will get along together. Nocturnal creatures should be watched the 

 first night. Many animals have a very definite sense of ownership 

 of their homes and resent intrusion by another. It is therefore 



