6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



tion, morphology, habitat, and ecology. Ecological data for the 

 Gerbillinae and Dipodidae are adapted from Ognev (1963), Petter 

 (1961), Zahavi and Wahrman (1957), and Kirchshofer (1958). Figure 

 2 compares the overall phylogeny for the three major families studied; 

 it is derived from the work of Ognev (1963), Herold and Niethammer 

 (1963), and Wood (1935). 



The desert-adapted species show wide divergences when reproduc- 

 tion, maturation rates, morphology, and ecology are compared. The 

 jerboas differ from the kangaroo rats in that some genera of jerboas 

 hibernate and the maturation of the young is prolonged. On the other 

 hand, the dipodids and the genus Dipodomys show a close parallel in 

 their morphology and habitat requirements. Certainly the closest 

 correspondence between rodent families occurs when some species 

 of gerbil (i.e., Gerbillus nanus) are compared with the heteromyid 

 species of the genus Perognathus. In any event, tables 2 through 5 

 emphasize the differences that may have a bearing on divergences in 

 the form of social organizations (see p. 31). 



Methodology 



When not under du-ect observation, the subjects were held as indi- 

 viduals or pairs in glass-sided cages with wire tops and wooden floors. 

 These holding cages were of two general sizes containing floor areas 

 of 90 to 180 square inches. The animals were fed a mixture of 

 sunflower seeds, commercial rat pellets, rolled oats, millet, and fresh 

 lettuce (see also table 1). 



The analysis of behavior began with a description of the discrete 

 units that comprise the total repertoire of activity patterns displayed 

 by the subject under study. In order to give the animal ample 

 opportunity to display the full range of its behavior patterns, simu- 

 lated natural habitat cages were employed. Such cages contained 

 artificial burrows ; they are fully described in a previous pubhcation 

 (Eisenberg, 1963b, p. 5). In the present study, the floor areas of 

 the burrow cages included three sizes: 864, 550, and 360 square inches. 

 Nocturnal forms were observed by a red light during their normal 

 dark cycle of activity. Once the behavioral units had been described, 

 the subjects were exposed to several testing situations that may be 

 treated under two headings: (1) behavior patterns of the solitary 

 animal and (2) patterns of social behavior. 



The beha\dor patterns displayed by the isolated animal fall under 

 the general categories of exploratory and maintenance beha\4or. In 

 order to analyze the differences among species, standard tests were 

 run by allowing an anunal to move freely in a glass-fronted arena 

 containing specific artifacts such as stones, hay, a tree branch, and 

 a small amount of food. The arena sizes included floor areas of 748, 



