20 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



the species included in this study and is not unique for the kangaroo 

 rats and jerboas. 



The encounter. — Encounters were run between males, females, 

 and between males and females. In general, male to male encounters 

 result in avoidance or in fighting, with the subsequent establishment 

 of a dominant-subordinate relationship. Female to female encounters 

 are less predictable and the most informative encounter type is that 

 between a male and a female (Eisenberg, 1962a, 1963b). For the 

 purpose of this paper, I will restrict the data to the male-female 

 encounters under two spatial conditions and two physiological 

 conditions. 



The spatial conditions include (1) an encounter in a neutral arena 

 and (2) an encounter in a territorial box (see p. 8) . Since the dimen- 

 sions of the encounter arena influence the outcome (Eisenberg, 1963b), 

 the dimensions will be specified in all tabidations. 



The two physiological conditions include (1) the estrous and (2) 

 the anestrous states of the female. In all discussions of male-female 

 encounters the male was judged to be in a sexually viable condition. 



For tabulation purposes the behavior patterns are often classified 

 into the following categories: contact promoting, sexual, and agonistic. 

 The composition of each category corresponds to the classification 

 presented on page 10. 



SoHtary Versus Tolerant Species: If we compare a series of en- 

 counters between males and anestrous females for different species, 

 we find evidence for a distinct separation into two social types. One 

 type either avoids contact or, if the arena space is small, engages in 

 agonistic behavior. The second type initiates contact-promoting 

 behaviors such as grooming. Table 10 lists the totals and average 

 frequencies of bouts of the major behaviors displayed during encounters 

 in a neutral arena or a territorial box. A tolerant species such as 

 Peromyscus maniculatus gambelii engages in a grooming bout ap- 

 proximately once per encounter even in a territorial encounter, whereas 

 a sohtary species in a neutral encounter avoids contact aside from the 

 naso-nasal. Tables 11 and 12 demonstrate a similar separation into 

 contact-prone and avoidance-prone social types, although here the 

 data are selected from a carefully controlled series that utilizes 

 the neutral arena and the territorial box experiments. In the latter 

 situation, contact-promoting behavior drops even further and agonistic 

 aspects become more apparent. 



An inspection of tables 11 and 12 suggests that Meriones un- 

 guiciilatus, Gerhillns gerbillvs, and Alladaga elator are more contact- 

 prone, whereas Dipodomys panamintinus, Perognathus calif ornicus, 

 and Gerhillus nanus are more avoidance-prone when the female is in 

 an anestrous condition. 



