NO. 3597 RODENT ETHOLOGY — EISENBERG 9 



berg, 1963b, p. 4). The encounter boxes included 1110, 1728, and 

 1950 square inches of floor area. Utilizing this technique, some 

 measure of the influence of the locus on the outcome of an encounter 

 could be assessed. 



(3) The formation of social groups: In this situation pairs or 

 groups were allowed to remain together as a result of either a sinuil- 

 taneous or a territorial encounter. Several measurements were re- 

 corded, including the tendency to nest together, the incidence of 

 wounding, the tolerance of the male by a female during parturition and 

 rearing, the effect of the male on the female's estrous condition, and 

 the effect of the adults on the survival, growth, and development of the 

 young. Various cage sizes were employed in the study of the pairing 

 tendencies and the social tolerance during the growth of confined popu- 

 lations. These included cages with floor areas of 180, 328, 550, 864, 

 1110, 1728, 1950, 2304, 5040, and 6480 square inches. Studies of this 

 nature yielded information concerning species-specific differences in 

 social tolerance. Pair tolerance and the growth of confined popula- 

 tions varied from species to species; the solitary species required a 

 large space coupled with a complex environment in order to reproduce 

 successfully. 



Terminology 



As the hiitial analyses progressed, it was found that the behavioral 

 repertoires of the different species were remarkabl}^ similar in their gross 

 form. The social behavior of small nocturnal mammals appears to 

 include a reliance on auditory, tactile, and chemical communication, 

 with a reduced role for visual communication. Hence, the evolution 

 of complex movement patterns with concomitant morphological 

 changes that are employed in the visual display of many diurnal verte- 

 brates such as bu'ds, lizards, and certain fishes are reduced in the pres- 

 ent group. The role of chemical and auditory signals in the nocturnal 

 rodents is still poorly known and, in the present study, the behavioral 

 units were recorded "\\'ithout direct reference to their communicatory 

 function. As a result, the beha\doral inventories show more uniform- 

 ity than might be expected by students of avian or fish behavior. 

 This uniformity permitted a single list of defined behavioral elements 

 to serve for all species. 



Complete ethograms exist for the heteromyid rodents (Eisenberg, 

 1963b), the genus Perom.yscun (Eisenberg, 1962a, 1963a, 1967), 

 Meriones persicus (Eibl-Eibesfeldt, 1951), and Gerbillus nanus (Kirchs- 

 hofer, 1958); in addition, ontogenetic data exist for Meriones tamari- 

 scinus (Ranch, 1957) and a behavior study of the jerboa is near com- 

 pletion by Hackmger (pers. comm.). 



Rather interesting data on the reproductive behavior of Pachy- 

 uromys duprassi and other gerbillines are contained in the early work 



